vO"0, — Vk^ Division of Agricultural Sciences UNIVERSITY OF CALIFORNIA ii»ivji:viuvii]ii:ui;i;ii]iii l!l»;ffl;1[fllHill:T:!IimiMra J, AZEVEPQ PRICE H.OO CALIFORNIA AGRICULTURAL Experiment Station Extension Service MANUAL 44 CAGMAM 1-110 (1974) As conservation of natural resources and reduction of environmental pollu- tion becomes daily more vital, the problems and potential values of livestock manures become increasingly more important to mankind. This publication presents an overview of the status of livestock manures, their interrelationship with society as well as with agriculturists, the problems they create, and the possibilities they offer as sources of energy and of soil enrichment. A comprehensive listing of literature on the above and related subjects is included and will be of value to laymen as well as to professional researchers, planners, and engineers. A general index of text material starts on page 105. August, 1974 The authors: J. Azevedo is Staff Research Associate, Department of Soils and Plant Nutrition, University of California, Davis; P. R. Stout is Professor in the Department of Soils and Plant Nutrition, and Chemist in the Ex- periment Station, Davis. THIS MANUAL is one of a series published by the University of California College of Agriculture and sold for a charge which is based on returning only a portion of the production cost. By this means it is possible to make available publications which, due to relatively high cost of production or limited audiences, would otherwise be beyond the scope of the College publishing program. Digitized by the Internet Archive in 2012 with funding from University of California, Davis Libraries http://archive.org/details/farmanimalmanure44azev CONTENTS INTRODUCTION 1 The historical role of animal manures in agriculture ] ANIMAL MANURES IN CALIFORNIA 3 Regional distribution of California livestock 3 Beef cattle 3 Dairy cattle 4 Sheep and swine 5 Poultry 5 Manure handling and utilization in California 5 Climatic determinants and manure handling 5 Economic determinants of manure utilization 6 QUANTITY OF MANURE PRODUCED BY DOMESTIC ANIMALS . . 8 Digestion and manure production processes 8 Daily manure production 8 Manure distribution per unit area and with time 10 Accumulation of manure 11 CHEMICAL CHARACTERISTICS OF ANIMAL MANURES 12 Nutrient intake and excretion 12 Distribution of nutrients in feces and urine 13 Chemical composition of animal manures 17 Alteration of mineral composition of manures during storage 19 Nutrients excreted per production cycle 19 PHYSICAL PROPERTIES OF ANIMAL MANURES 20 Volatile and fixed solids 20 Particle-size distributions 21 Particle density and bulk density 21 Flowability 23 Water-holding capacity 23 DECOMPOSITION OF ANIMAL MANURES 25 Animal digestion and decomposition processes 25 Decomposition processes 26 Changes in manure during decomposition 28 Management of decomposition processes 33 On-site composting 34 Stockpiling and composting 34 Aqueous treatment systems 35 Effect of bedding, feed additives, and manure amendments 36 NUISANCE FACTORS OF MANURES 36 Esthetics and public relations 36 Health aspects of manure nuisances 38 Dangers of manurial gases in confined quarters 38 Flies 38 Odors 42 Dust 43 Moisture-nuisance relationships 44 Feather, mosquito, and field-spread manure nuisances 45 EFFECTS OF ANIMAL MANURES ON WATER QUALITY AND WATER-BODY ECOLOGY 46 Water quality considerations 46 Manures in relation to fish kills 46 iii Plant nutrients in relation to eutrophication 47 Nirate and nitrite hazards to man and livestock 48 Manure additions to surface and underground waters 48 Direct discharge into waterways 4g Alternatives to direct discharge of wastes 49 Runoff from barnyards, corrals, feedlots, pastures, and rangelands 49 Leaching of contaminants from confined animal units and barnyards 52 Volatilization and reabsorption of ammonia 53 Minimizing water pollution through feedlot and barnyard management 54 Runoff and leaching of pollutants from land-spread manure 55 ANIMAL MANURES AS FACTORS IN DISEASE TRANSMISSION 56 Factors in the spread of disease 56 Diseases transmitted in animal manures 59 Animal wastes and disease prevention 61 PREJUDICES REGARDING USE OF ANIMAL MANURES 62 Esthetics and nuisances 62 Weeds 62 Problems associated with over-use of manure 63 Salts 63 Ammonia toxicity 64 Nitrate in forage 64 Adverse changes in botanical composition of pastures 65 Adverse changes in chemical composition of pastures 65 Zinc deficiency in orchards 65 Trace element accumulations in soils 65 Hormones in animal manures 66 FERTILIZATION WITH ANIMAL MANURES 66 Short-term yield comparisons 67 Long-term yield comparisons 68 Nutrient availability and recovery comparisons 69 Availability of manure nitrogen 69 Recoveries of manure nitrogen 71 Availability and recovery of phosphorus and potassium 74 MANURE AS A SOIL AMENDMENT 75 Supplementary nutritional values 75 Effect of manure on soil's physical properties 76 Aggregation 77 Permeability of soils 78 Soil compaction 79 Soil crusting 79 Water-holding capacity of soils amended with animal manures 30 Biological benefits to soils from manure amendments 81 Values of manure in land and water conservation 81 ALTERNATIVE USES OF MANURES 82 Manure as feed for animals 82 Manure as a source of fuel energy 84 Miscellaneous uses for manure 86 Disposal oi manure 87 SUMMARY 87 LITERATI RE CITED 89 INDEX 105 i\ FARM ANIMAL MANURES: AN OVERVIEW OF THEIR ROLE IN THE AGRICULTURAL ENVIRONMENT "A well-kept manure pile or improved methods of handling this product on the farm are not only a sign of thrift, but also an indication that the farmer is an intelligent operator who understands his problem and is interested in the permanency of agri- culture." F . J. Sieve rs INTRODUCTION Animal manures are inescapably a part of daily life. Manures, including those from humans, are ever present and always a concern to someone — whether farmer, or parent responsible for rearing children from infancy through the "diaper years." Except for cases of unforeseen lack of an appropriate method of disposal, the prob- lem of what to do with one's own excre- ment may be scarcely noticed for the greater part of one's lifetime. Although the average citizen of this day and age escapes the tasks of handling and manag- ing his own manurial wastes, sanitary engineers, plumbers, and public health officials and the community do not. Similarly, the day-to-day concerns for the disposition of manures from our do- mesticated livestock and poultry are re- stricted mainly to managers of animal industries. Yet the over-all problems of their use or disposal are of consequence for society in general. In the U. S., the dry-weight ratio of animal manures to human manures produced is about six to one. This estimate is based upon the amounts of protein-nitrogen consumed by the human population and the amounts of vegetable-protein that have to be eaten by animals in order to provide the known amounts of animal-protein that U. S. cit- izens are consuming. On a wet-basis the magnitudes of ma- terials to be handled from animal versus human excretions is reversed because of the large amounts of water used to trans- port human excretion to sewage treatment systems. The U. S. is about 80 per cent sewered, so that for the country as a whole, fresh volumes of animal excretion are only about one-tenth the volume of water-suspended human excreta. Under new environmental planning, suggestions are made frequently that water from sew- ers be spread on land rather than being diverted to streams, lakes, bays, or oceans. Therefore, the ways that human and an- imal excreta are managed and utilized in the future will be of importance to agri- culture and the agricultural produce sup- plied to people living in the U. S. The historical role of animal manures in agriculture Historically, manures from domestic an- imals changed from waste of little conse- quence to carefully husbanded fertilizers as increasing human populations de- manded more food from fixed amounts of land. Eventually, food demands out- stripped available land and manurial fer- tilizer capacities so that there were eco- nomic incentives first for manufacturing phosphatic chemical fertilizers and then for the more costly synthesis of fixed ni- trogen, both as nitrate and ammonia. With cheap natural gas for ammonia synthesis coming into plentiful supply, and with in- creased food-supplying abilities of larger- scale mechanized agriculture, manufac- tured fertilizers not only filled a develop- ing gap in the fertilizer requirements of still-increasing human populations but also brought prices of fertilizers down to less than costs of handling and spreading the same amounts of available nitrogen in animal manures. As a result, consumers in the U. S. paid proportionately less of their income for food than ever before, while at the same time they increased the quantity of animal-protein in their diet by markedly increasing consumption of meats and decreasing consumption of cereal grains and potatoes. Per capita consumption of eggs, poultry, and meats increased from about 175 pounds in 1910 to about 250 pounds in 1970, whereas per capital consumption of cereal grains 1 CHANGING DIETARY PATTERNS WITHIN THE USA: 1910 ~ 1968 300 POUNDS PER 200?^ CAPITA 00 eggs *e Pof ot^: ............ ues and potatoes 300 200 100 1910 '20 1930 '40 1950 '60 1970 MEATS 500 + POULTRY + 400 EGGS (Hundreds of 300 Millions of Pounds) 200 PROTEI N - FOOD AND FARM-SITE NITROGEN IN I 1910 - 1968 POPULATION (Mi 1 1 ions of Persons) 100- 1910 '20 1930 "40 1950 '60 1970 Metric system conversion factors Pounds x 1/2.2 = kilograms Tons x l/l.l = metric tons Fig. 1 . Relationship of changing dietary patterns to farm-site nitrogen requirements (from Stout, 1972). and flour fell from 300 pounds to about 130 pounds during the same 60-year span (fig.i).' The eharacter of the animal industry changed markedly in meeting consumer demands for animal products. Animals that formerly would have been left on pastures and rangelands were confined in order to reduce labor costs and to in- crease feed-conversion efficiencies. These confinement areas increased gradually in number and size, and by 1968 more than 67 per cent of our beef came from feedlots (Viets, 1971). Specialization for economic efficiency in agriculture also resulted in the disinte- gration of the traditional close-knit bonds between crop production and animal pro- Ms Stout (1972) pointed out, the 1968 U. S. dietary mix included 99 grams of protein per capita- flay, 68 grams of which came from animal sources. In contrast, the 1910 American diet contained almost as much total protein (97 grams) hut only 49 grams of this was from animal sources. Manure from those animals consumed in 1910 would be less per capita than that from such animals consumed in 1968. Manure production in the U. S. could be reduced further if each person consumed an average of only the adequate 65 grams of protein per day, or even further if the animal portion of the 65 grams was garnered from milk and egfis (from high-efficiency animals) rather than from beef. Of course a Btricl vegetarian diet would essentially eliminate animal manure from being a domestic problem. Between these extremes, the manure produced is proportional to animal-products consumed, adjusted by animal-feed conversion efficiencies. Such arc the alternative prospects for reducing II. S. animal manures by dietary choice alone. 2 duction. Animal feeds formerly grown on the farm from which animals were also marketed are now being imported from remote distances, yet the manure is de- posited locally. It is in this context that animal manures have shifted gradually from being in eco- nomic demand as fertilizers to materials of comparatively little value. With the increasingly unfavorable eco- nomic climate for the utilization of un- cherished, accumulating manures, less care has been taken to manage such wastes, and this led to environmental problems associated with unsuitable meth- ods of manure storage and disposal. En- croachments of suburbs into what were farming areas make the usual livestock nuisance problems of flies, dust, and odors more critical as environmental issues. Thus, along with many other operations having recognizable impacts upon envi- ronmental qualities in the 1970's, waste from animals presents management prob- lems that will have to be solved. The major stumbling block is that the costs associated with the solutions will have to be reflected in the food-price structure. Although there are those who despair of finding new uses for manure, animal manures may well find places in other phases of our economy as fuels, if non- renewable energy resources from fossil fuels are depleted further and become more expensive. Although sufficient tech- nological "know-how" on transforming manures into readily salable products is available today, further research and de- velopment will be required before factories can be designed to make such conversions economically feasible. Of course, higher costs of fuels may make manures again competitive with chemical fertilizers. ANIMAL MANURES IN CALIFORNIA Regional distribution of California livestock Increasing quantities of animal manures are being produced in California as a result of animal industries growing to meet increasing demands for meat, dairy products, and eggs. The California Crop and Livestock Reporting Service reports 3,921,000 beef cattle, 789,000 dairy cattle, 956.000 sheep, and 151,000 swine occupy- ing California's rural and semirural areas in the first part of 1973. Figure 2 shows the distribution of these animals for eight regions of the state; their com- bined manure production amounts to a considerable tonnage. Although much of this manure is returned naturally to range- lands and pastures by grazing animals, the greater and still increasing proportion is being produced in confined livestock-feed- ing facilities. Manure accumulating in confinement areas is more visible than manure dropped in the field and thus is more immediately a cause of complaints. In addition, manure produced in confine- ment requires labor and energy to collect. transport, store, treat, or otherwise con- vert the waste into a usable product and to prevent environmental pollution in the interim. 2 Beef cattle. California's almost 4,000,- 000 head of beef animals represents 3.6 per cent of the nation's beef population. About 1.2 million cattle are kept in con- fined feedlot facilities, and over 2.000.000 were marketed from California feedlots in 1972. Beef feedlots are located mainly in the low desert valleys l Imperial. Coa- chella. Palo Verde ) and the San Joaquin Valley with lesser numbers in the Salinas and Sacramento Valley areas. Cattle in the Imperial Valley area alone account for more than 40 per cent of the feedlot beef in the state. Most Californian cow-calf operations connected with beef-cattle raising are scat- tered throughout the rangelands of the central Coast Range mountains, the foot- hills of the Sierra Nevada, and the range countrv of northeastern California. * Animal manure problems are not restricted to agricultural operations as any person walking through city streets or parks can attest. Djerassi et al. (1973) report a national dog and cat popula- tion of 66 to 80 million animals, about one for even- three people. Daily excretions of dog manure in the U. S. includes 3,500 tons of feces and 36 million liters of urine (Djerassi et al., 19731. California is the state with the highest population of dogs and cats. / | CATTLE 98 4 / / DAIRY 2 2 j£ J SHEEP 7 9 J f SWINE 3 J I CATTLE 136 3 / / (3 count i es ) 1 1 DAIRY 4 1 1 SHEEP 12 4 J ---'I SWINE ' 9 l\ ^ »4 CATTLE 323 9 | I ( 3 counti es ) / 1 1 DAIRY 38 8 | / 1 / SHEEP 286 5 I / / f*\ SWINE 13 9 * 1 ■ 1 (B counti es ) * 1 FARM ANIMALS I in t CALI FORNIA - 1973 CATTLE 160 7 X DAIRY 1 \ totals + CATTLE 98 1 |Yk / DAIRY 18 3 1 ^ I SHEEP 78 9 ' 1 V SHEEP 2 ° 4 \ Cattle 3921 t XsWINE 2 1 X \ (II counties) ^ Dairy 789 SWINE 3 5 1 1 ( 3 counties) ^^y 1 A ^y V \ Sheep 956 \ \ Swine 151 t CATTLE 1336 1 ! \ DAIRY 411 1 \ SHEEP 363 3 1 \ SWINE 68 2 \ \ CATTLE 678 8 V 1 ( 8 counties) j X^ DAIRY 81 7 ^^ SHEEP 130 4 J SWINE 27 8 ^ ( 13 counties) M^J^ ^^ CATTLE 1098 8 | \^^ DAIRY 235 5 \ J SHEEP 56 2 \ \*^ SWINE 30 6 ^ ^^ (8 counties) w Al 1 numbers in thousands t Not including dai ry cattle t Figures of December. 1972 Source California Crop and Livestock Report mg Services ^^^^^^^^^^^^^mj Fig. 2. Regional distribution of livestock in California, 1973. Dairy cattle. The 789,000 dairy cattle in California represent 0.8 per cent of the nation's dairy animal population. Califor- nia's dairy cows produce a yearly average of 13,406 pounds of milk and 18 tons of fresh manure per head. Dairying operations in the southern half of the state are located mostly in the San Joaquin Valley (52 per cent of the state dairy cow census) and the Chino- Corona Basin area east of metropolitan Los Angeles. The substantial milk produc- tion areas of northern California include the Sonoma-Marin area north of San Fran- cisco, Glenn and Sacramento counties in the Sacramento Valley, and the Eel River area south of Eureka. Most California dairies are still inte- grated with pastures although in some areas, where land prices are high or where owners favor dry-lot designs, only vestiges of pastures surround the dairy. This in- creased confinement situation is most ev- ident in the Chino-Corona liasin area of western Riverside and San Bernadino counties where 380 dairies ( 143,000 cows ) are situated on only 37,065 acres (15,000 hectares) of land (Luebs et al., 1973). Most of these (365 dairies) are located within a 17,000-acre area (Adriano et al., 1971a). An average, modern dairy will use about 35 gallons (132 liters) of fresh water daily for pre-milk washing and milk- ing parlor sanitation for each cow (Adri- ano et al., 1971a) . The water, which by then is contaminated with manure, offers another disposal problem for the dairy. Sheep and swine. The numbers of sheep in California, while 6 pe~ cent of the U. S. total, have been declining in re- cent years. Most sheep are on range and pasture land, with few in confinement. The foothills of the Sierra Nevada along the eastern edge of the Central Valley are California's main sheep production area. Swine numbers in California are also down, and California swine account for only 0.2 per cent of the U. S. total. The San Joaquin Valley is the major swine pro- duction area in the state, with lesser num- bers located in Riverside county and along the central and southern coast. Most swine are kept on solid or slotted concrete floors, and water-flushing is commonly an integral part of pen sanitation. Poultry. An average of 39.2 million laying hens kept on California ranches pro- duced 721 million eggs in 1972. The ma- jority of laying hens are distributed in large arcs around the Los Angeles-San Diego metropolitan area in the south and the San Francisco Bay Area, including the northern San Joaquin Valley, in the north. Laying hens are confined in suspended wire cages. California fryer production, totaling over 86 million birds (more than 361 mil- lion pounds) in 1972, is centered in the Stanislaus-Merced county area with lim- ited production in the southern San Joa- quin Valley and northern Los Angeles county. Chicks are grown on absorbent litter with about three-quarters of a square foot of space per bird. Usually the surface layer of litter is skimmed off after each brood and the entire litter is replaced at least twice a year. Fryers are marketed 8 or 9 weeks after hatching. California turkey growers produced 16.8 million turkeys in 1971. Turkey ranches are located mainly in the central San Joa- quin Valley counties with other major con- centrations in Los Angeles, San Bernar- dino, and Riverside counties. Manure handling and utilization in California Climatic determinants and manure handling. Climatic variables in different parts of the state suggest some unusual advantages in handling manure in dry cli- mates as well as limitations on manure handling methods in more humid areas. In the northern and central areas of Califor- nia, fly and odor nuisances are more diffi- cult to control because of relatively heavy winter rainfall and, along the coast, higher humidities from frequent summer fogs. Numerous northern California dairies have installed holding-tanks for temporary, minimal-nuisance storage of manurial liq- uid wastes. Sprinkler irrigation is a fav- ored method of slurry distribution as it is undesirable and difficult to haul the mate- rial into fields with trucks or tractors in wet weather. Bedding is sometimes added to corral and barn areas to reduce nui- sances associated with muddy conditions. In drier times of the year, solid wastes are scraped from corrals and spread upon nearby fields as soon as possible — usually just before fall or spring tillage. Although there is some liquid-handling of poultry wastes in humid areas, drop- pings are predominantly handled as solids. Rain water can usually be kept from accu- mulating below covered poultry houses, and limited natural drying is possible. Fre- quent hauling and stockpiling or thin- spread drying of the manure is desirable during the fly season. Enclosed poultry houses minimize fly troubles, and deep-pit housing of fly-tight construction with an inside pit for accumulating manure has met with some limited success in wetter climates. Aridity increases with decreasing lati- tudes in California, and this aridity offers additional advantage for natural drying of manures. Although dry manure may re- quire dust-control measures, it is less odor- ous and less attractive to breeding flies. However, this advantage may be offset by increased breeding activities of flies in warmer temperatures. There is less weight of material to be handled in dry-manure systems, and solids are easier to move and transport with conventional equipment. In moving south, animal housing is found to be of more open construction, but this hous- ing advantage is somewhat offset by in- creasing needs for shades to protect ani- mals from the sun. San Joaquin Valley dairies are especially adapted to storage of liquid wastes in large holding-ponds because water from hold- ing-ponds can be incorporated into routine irrigation programs and common irriga- tion systems. Some dairies re-use holding- pond water for flushing walkways and feeding areas before applying the enriched water to the land. Most dairy solids are scraped, hauled, and spread onto neigh- boring land. Poultry manure is also handled effec- tively as slurries stored in holding-ponds, with the holding-pond liquors incorporated into the farm irrigation system. There are fewer liquid-manure handling systems and more dry systems in the southern counties because of their warmer and drier climates. Beef cattle feeding and finishing in Cali- fornia takes place almost exclusively within open corrals. Sun-shades are beneficial in the Central Valley and necessary in the southern deserts (Clawson, 1970a). Ma- nures are scraped from the pens during dry weather and stockpiled and/or hauled away and spread in fields. Manure accu- mulations around fence-posts and shade- posts require special attention because they are usually inaccessible for cleaning by powered scrapers and fly-larvae can ma- ture in large numbers if accumulations re- main moist. Economic determinants of manure utilization. Manure has changed from an economic asset to essentially an economic liability in the last 30 years, mainly be- cause the costs of scraping, processing, stor- age, hauling, and distributing bulky ma- nures of low plant nutrient content have continued to increase while costs of high- grade commercial fertilizers — particularly nitrogen fertilizers -have declined sharply until just recently. Additionally, the quality of manure could not always be assured from one season to the next. Bulk, weed- seed risks, and other inconveniencing fac- tors of ili'-. odors, and dust have resulted in decreased demands lor animal manures a fertilizers. As a consequence, a few ani- mal growers are now looking to sanitary land fills, incineration, ami high disposal- rates of land applications as means of re- ducing costs of manure disposal. In the in- terests of resource conservation, however, animal manures should be utilized when possible so as to conserve plant nutrients and prevent pollution resulting from inade- quate disposal techniques. Sorely needed research on how best to defray the cost of handling and distribution is in progress. In spite of the current difficult economic climate for sale of manure as fertilizers, at least nine-tenths of the animal manure produced in California is being distributed on crop-land. In agricultural valley areas manures are applied to orchards, vine- yards, and truck crops as well as to crops grown for animal feeds. Two or three tons of manure per acre is the commonly recommended yearly application for or- chard crops, while irrigated truck crops often receive 10 to 15 tons per acre for each crop. ( Some farmers use much less or more than the recommended amounts, depending upon their individual prefer- ences.) There are, in addition, extensive farm lands in California where applications of manure could and would be made were it not for high costs of transportation. Cali- fornia's vast acreage of rangelands could absorb all available manures were it not for the costs of transportation and spread- ing. In parts of San Diego county some poultry operations have relocated from coastal areas to such rangelands, to the benefit of both the poultry grower and the rangelands (McKell et a/., 1970) . A calcu- lation of the manure produced by confined animals in each county (Anon., 1968a), and of farm acreage (U. S. Bureau of the Census, 1967), reveals few counties in California where annual production of ma- nures is greater than about 1 ton of fresh animal manure per acre of farmland (fig. 3 ) . The county maximum is 2.8 tons per acre. However, as only relatively short hauling distances of bulk manure is eco- nomically feasible, the value of manure to the animal producer is highly dependent on local supply of and demand for manures. Currently, animal growers in the San Joaquin Valley can usually break even or even make a small profit by selling their manures for use on nearby newly-planted vineyards. Where manure production is out of balance with fertilizer needs of farms within economic hauling distances (usually less than 10 miles), manure re- moval sometimes has to be subsidized by the animal grower. For example, fcedlot (> Marin 1968 manure production figures 1964 land census figures Fig. 3. California counties having over 0.95 tons of fresh animal manure produced yearly for each acre of farmland. operators in the Imperial Valley have been paying from $0.50 to Si. 50 per ton for manure removal. The major manure hauler in the desert valleys removes 400,000 tons of manure from area feedlots annually; skillful marketing, materials handling, and logistics are necessary in arranging for the distribution of such huge quantities of ma- nure within the relatively limited economic- hauling reaches from feedlots. The hauling company derives its profit from providing cleaning services to feedlot operators and hauling and spreading services to farmers. Increasing supply and decreasing demand have affected cattle manure values ad- versely in other western and midwestern states (Stubblefield, 1966; Badger and Cross, 1971). The exodus of dairies from Los Angeles suburbs to the Chino-Corona Basin area of Riverside and San Bernardino counties re- sulted in oversupplies of manure in a lim- ited area. Manure from dairy farms in the Chino-Corona Basin would amount to about 180 tons of fresh manure yearly for each acre of irrigated pasture in the Basin (Adriano et a/., 19716), so dairymen in that area are searching for other-than-fer- tilizer uses for dairy manures. Numerous alternative uses of manure have been proposed (pages 82-87). I su- ally, the- capital investment and other costs of converting manure into a salable product such as gas, oil, or a building material dic- tate against attempting to build plants for such conversions, particularly when the product would have to face strongly com- petitive markets. If prices of traditional sources of energy continue to rise, conver- sions of manure into fuels, which is al- ready technologically feasible, may become economically realistic. However, the more immediate hope for useful recycling of ani- mal manures lies in their direct agricul- tural use. Increased values of animal manure as a soil amendment, and as an animal feed nutrient source in addition to established values as suppliers of plant nutrients, can increase the demand for manure. Animal growers might also profit by taking into account the supply and demand potentials for animal manure when considering new locations for large-scale animal feeding operations. Cooperation between livestock operators and the growers of animal feeds in order to expand manure recycling should be en- couraged for they have equivalent stakes in the ultimate market for meat, dairy products, poultry, and eggs. QUANTITY OF MANURE PRODUCED BY DOMESTIC ANIMALS Digestion and manure production processes Domestic livestock are selected and bred primarily for their efficiency in converting vegetable matter into animal products de- sired for human consumption. However, there are certain inefficiencies inherent in these conversions: some of the energy of animal feeds is dissipated in body-mainte- nance processes, and much of the feed is not metabolizable and is excreted as ani- mal wastes. Animal digestion processes (pages 25- 26 ) convert complex molecules of plant proteins, carbohydrates, and fats into simpler molecules that can be absorbed from the digestive tract. The amounts of plant material that can be transformed to meat or other animal products is limited by the composition of the ration, the size of the digestive tract, rates of conversion, and the activities of microbial populations inhabiting the digestive tract. The more slowly digestible plant materials are ex- creted in the feces, accompanied by en- zymes, mucous cells of the digestive tract, and the living and dead bacteria that were associated with digestion processes. Ani- mal urine contains wastes from the cellular metabolism of absorbed feed nutrients as well as surplus salts and water. Daily manure production Table I shows representative recent 1 I960 1971 ) data on daily manure pro- duction by various species of confined do- mestic animals fed on modern rations. This table illustrates the great variability that must be considered when generalizing about quantities of manure production. Such variations stem from the size and age of the animal, the type and amount of its rations, its productivity, its innate indi- viduality, and from experimental variables such as methods of manure collection and storage. Data from trials conducted more than 10 or 15 years ago should not be expected to represent current production quantities (Agnew and Loehr, 1966; Taiganides and Hazen, 1966) . In fact, re- cent innovations in animal confinement and formulation of rations tend to obso- lete data more than 5 or 7 years old. Less manure is being produced per beef, pork, or broiler animal than was the case 30 years ago because of improvements both in ration digestibility and reduction of stress upon the animals. In contrast, dairy cows and hens seem to be producing more manure per animal because feed intake required for increased individual produc- tion of milk and eggs has more than offset higher conversion efficiencies from im- proved ration formulation, reduced stress, and restricted movement (hiring confine- ment. However, manure produced per pound of milk, eggs, or meat is still lower than for any previous era. Manure production for any species of growing meat animal is largely a function 8 Table 1 QUANTITY OF MANURE PRODUCED BY MAJOR FARM ANIMALS Type of animal (and reference source) Daily manure production Raw manure Dry matter Beef: Hart (1960) Taiganides and Hazen( 1966)* . . Hore and Pos ( 1967) Wadleigh(1968) Hegg and Larson ( 1971) . . . . Taiganides and Stroshine (1971)t Dairy cow: Hart (1960) Sobel (1966) (avg. of 18 ref.)* . Dale and Day (1967) Hore and Pos (1967) Scholz(1971) Taiganides and Stroshine ( 1971 ) Swine: Taiganides and Hazen (1966) . Kesler(1966) Hore and Pos (1967) Conrad and Mayrose (1970) . Scholz(1971) Taiganides and Stroshine (1971) Sheep: Taiganides and Stroshine (1971) Horse: Taiganides and Stroshine (1971) Hen: Hart (1960) Eno(1966) Moore et al. (1964) Ostrander(1966) Taiganides and Hazen (1966) . Sobel (1966) (avg. of 18 ref.) . Hore and Pos (1967) Scholz(1971) Taiganides and Stroshine ( 1971 ) Broilers: Hore and Pos (1967) Gerry (1968) Taiganides and Stroshine (1971) Turkey: Taiganides and Stroshine ( 1 97 1 ) 60 64 72 29 46 80.6 86.1 107.8 99 139 7.9 7.7 5.1 44.2 0.37 0.38 0.24 0.25 0.25 0.32 0.41 0.29 0.36 0.20 0.79 en. ft. 1.0 0.75 1.3 1.5 0.14 0.006: 0.004 0.004: 0.0023 9.0 10.2 4.6 7.9 12.1 11.2 13.5 13.9 13.8 1.1 1.2 1.0 1.5 17. 0.05 0.21 per cent oj fresh \\ eight of manure 15 16 27 17 15 13 12 14 9.5 16 10-15 9.7 13 40 0.10 28 0.06 26 0.07 29 0.08 25 0.11 27 0.07 24 'Figures reported by these authors are averages of some values given by other authors. higher food inputs, and ordinarily pro- of its body weight, with larger animals producing greater quantities of manure. Mature animals that eat only enough for body maintenance will excrete proportion- ately lesser amounts of manure. Laying hens, lactating cows, or all pregnant or nursing animals require correspondingly duce greater amounts of manure. Moisture is the largest weight compo- nent of freshly-voided manure. The amount of water contained in feces is de- pendent on the species, although water contents of feces remain fairly constant TABLE 2 DISTRIBUTION OF RAW MANURE. DRY MATTER, AND WATER BETWEEN URINE AND FECES OF VARIOUS FARM ANIMALS Livestock species Manure component Horse Cattle Sheep Swine Total raw manure* per cent excreted as feces per cent excreted as urine 81 19 91 9 79 21 71 29 88 12 70 30 63 37 82 18 55 45 63 37 Dry matterf per cent excreted in feces per cent excreted in urine 92 8 Water}" per cent excreted in feces per cent excreted in urine 59 41 'Values averaged from those given by several authors. ["Calculated from Salter and Sehollenberger ( 1939). within each species. Excretion of water in urine is highly dependent on water intake, which in turn depends on rations, physical environment, and animal individuality. Water intake and excretion has been found to be directly related to salt in the diet and drinking water of cattle (Weeth and Hun ter, 1971) and chickens (Hartman, 1962; Charles, 1970). Wilson (1948) found that water consumption of pullets exposed to temperatures of 95°F (35°C) was double that of birds exposed to temperatures of 70°F (21°C). Relative distributions of raw manure, moisture, and dry matter excreted in the feces and urine of certain farm animals are shown in table 2. A great proportion of water eliminated by horses and cattle is excreted in the feces, whereas sheep and swine excrete most waste water via their urine. Proportionately less dry matter is excreted in the urine of swine than other animals, so swine urine appears to be espe- cially dilute. The feces and the urine of poultry are mixed in the lower digestive tract (cloaca) and excreted as one mass. From -indies on chickens with modified ureters, Dixon (1958) determined that about 55 to 58 per cenl of fresh poultry manure was mine. I rine production may he highly \ ariable. Composition of rations formulated for particulai species has a noticeable effect on total manure production since the bal- ance of nutrients and energy of any par- ticular ration will affect its digestibility and the amount of waste excreted. Ma- nure excreted per pound of feed consumed can be measured or calculated from di- gestibility data by assuming that all in- digestible matter is excreted in the feces. Table 3 shows some measured and cal- culated data on manure waste per pound feed consumed, and comparisons of amounts of manure per pound of gain or product produced. Manure distribution per unit area and with time In studies of actual area covered by cattle droppings in pastures, spot depositions of manure and manure distribution in en- closed areas were examined by Johnstone- Wallace and Kennedy (1944) . They found that beef cowpads ranged in size from 78.6 to 113.] square inches with an average of 96.5 square inches. Other reports have shown that sizes of dairy cowpads aver- aged about 1 square foot, whereas urine spots often covered 3 square feet (Petersen et cl., 1956a). In another study, Borne- nr'ssza (I960) reported that manure pads from pastured cows also averaged about 1 square foot (155 square inches), but those from cows on dry feed were 124 square inches and those of cows fed silage average 186 square inches. Manurial spots arc more common along fence lines and near watering places (Petersen et al., 1956a). The distribution of beef cattle manure in confined pens has been studied with the aid of slotted floors. Hegg and Larson I l ( )7l ) found that where feed and water were offered on the same side of the pens, 10 Tabu 3 COMPARISON OF AMOUNT OF MANURE PRODUCED WITH AMOUNT OF FEED CONSUMED AND AMOUNT OF USABLE PRODUCT PRODUCED Pound manure per pound of feed consumed Type of animal (and reference source) fresh-weight basis dried-weight basis Pound manure per pound of product Beef: Hart and McGauhey ( 1964) Taiganides (1970) 1.73 1.04 1.41 0.25 (estimate) 0.16 0.46 0.24 0.22 6 25 lb. lb. gam 5-20 lb. lb. gain Gilbertson et al. (1970) Dairy cow: Ridker (1972) 1928 4.3 lb. lb. milk 1968 2.6 lb. lb. milk Dale and Day (1967) 2.54 1b. lb. milk Swine: Conrad and Mayrose (1970) Hens: White etal. (1944) Moore et al. (1964) 4.8 lb. lb. eggs 5 lb. lb. eggs Taiganides (1970) Bressler and Bergman (1971) Broilers: Gerry (1968) — cockerels pullets 63 per cent of the feces and 56 per cent of the urine were excreted on that half of the pen. When water and feed were placed at opposite sides, 53 per cent of the feces were found on the half near the feed and 62.6 per cent of the urine was excreted near the water source. Chang et al. (1973) mea- sured depth of manure accumulations at various points throughout an open, non- surfaced dairy corral. Fifty-seven per cent of the manure was concentrated close to feed and water and in an area of less than thirty per cent of the total corral surface. These data could he used in designing catchment and treatment facilities under slotted-floor pens, or to help assure more even manure distribution in open pens. Wolf (1965) gave considerable thought to animal psychology in his recommenda- tions for the design of swine production units for efficient manure removal. Swine seem to have fastidious dunging habits and will defecate at one end of the pen and sel- dom where they sleep or feed; they uri- nated in their sleeping quarters only if temperatures rise above 80°F (27°C) . De- sirable dunging habits can be encouraged by arranging for long, narrow pens, with fewer pigs in smaller pens with the water and dunging areas at opposite ends, and by floor-feeding of limited amounts of food rather than free choice. Most of the floor can be solid, with a slotted area covering a flushing channel at one end. Animals will defecate mostly during the daylight hours and more often when dis- turbed or excited. Beef cows on pasture were found to defecate 12 times daily and urinate 9 times daily (Johnstone-Wallace and Kennedy, 1944) . Five studies refer- enced by MacLusky (1960) indicated that dairy cows defecate an average of 13 times daily (12.6) and urinate 10 times (9.5). Caged laying hens excreted about 20 times daily (Tyler 1958). Accumulation of manure Basic data on manure production per an- imal can be used in predicting loads for manure handling and disposal systems. Liquid or semi-liquid systems especially are amenable to volume calculations based on average manure production figures. In order to arrive at necessary liquid storage and handling capacities, one need only multiply the daily volumetric production by the animal-days of service for the facil- ity and allow for additional volume if 11 water is to be added to liquify the manure (HoreandPos, 1967). If liquid systems are not used, manure production figures must be adjusted to ac- count for changes in weight and volume between the times of excretion and the final handling. For example, in dirt-sur- faced cattle feedlots the fresh and dry feces and urine get mixed with the soil to vari- ous extents depending on climate, animal density, and the physical character of the surface. The excreted moisture is generally distributed unevenly throughout the lot, and organic matter is oxidized at various rates depending on temperature and mois- ture conditions. Gilbertson et al. (1970) scraped 1.3 to 5.8 times the predicted weight of dry matter from some cattle feed- lots because soil material contributed sub- stantially to their scrapings. Ottoboni ( 1971 ) estimated that commonly one ton of cattle manure per animal-year must be removed from southern California feed- lots. Grub et al. (1969a) removed 0.2 to 1.2 tons (depending on ration digesti- bility) of accumulated cattle feedlot waste for each animal-year. Some dairy farms and most broiler pro- duction units use litter in their production systems; addition of litter or bedding into the systems means that more waste ma- terial has to be handled. The quantity of litter used for broilers during one growing period can amount to twice the weight of actual manure produced during that pe- riod (Gerry, 1968). Water can also present a disposal prob- lem for dairies. Adriano et al., (1971a) estimate that an average southern Cali- fornia dairy will use 132 liters (35 gal- lons) of wash water per cow-day. Although some dairies have re-used this water to advantage in the liquid handling of ma- nure, water is just more material that must be handled and disposed. Water will evap- orate from manure during storage, but may also be spilled from drinking cups or troughs, thus adding moisture to the ma- nure. Water loss in manure can be acceler- ated by good engineering design and by management that minimizes spillage or in- creases natural drying. Manure-production figures plus post- excretion changes in composition, are fac- tors that have to be taken into account when systems are designed for most effec- tive, economical manure handling. CHEMICAL CHARACTERISTICS OF ANIMAL MANURES if manure is to be considered as an eco- nomic asset, its physical properties and chemical content, including chemical-en- ergy, arc basic in calculations of its intrin- sic worth. Similarly, if manure is to be treated as waste, its energy and nutrient content will have bearing upon the accept- ability of places and methods for disposal. The values presented in the tables on pages 15 17. 20 for animal-waste characteristics. whether estimated, calculated, or meas- ured, arc not fixed entities. Representative numerical values in the future may have to be changed to correspond with alterations in rations and in methods of handling. Nutrient intake and excretion Animals arc fed balanced rations consist- ing mostly of plant materials and Mime organic and mineral supplements. Carbo- hydrates, proteins, ami fats arc metabo- lized l»\ animals for growth and mainte- nance, and for production of meat, milk. eggs, wool, hides and other products use- ful to mankind. Additionally, approxi- mately 40 mineral elements are cycled from soil to plant and through the animal, although less than half of these are known to be necessary For plant or animal growth .or survival. A growing or lactating animal obvi- ously requires more nutrients per unit of body weight than are required merely for body maintenance of an adult animal. Each 100 pounds of body weight gain in a growing steer requires approximately 2.4 pounds of nitrogen. 0.8 pound of phos- phorus, ami 0.2 pound of potassium. One thousand pounds of milk contains about 5.5 pounds of nitrogen. 0.9 pound of phos- phorus, and 1.5 pounds of potassium, among other nutrient elements. Organic and inorganic nutrients not retained by the animal for maintenance, growth, or 12 Table 4 PER CENT OF FED NITROGEN, PHOSPHORUS, AND POTASSIUM RECOVERED IN ANIMAL MANURES Type of animal Nutrient element Dairy* .... Steer* .... Heifer* . . . Sheep* . . . Pigs* .... average Steert .... Grazing cattlej 74 75 78 68 72 73 80-89 75 per cent recovered 61 85 78 87 83 79 70 79 75 82 87 86 92 90 87 80 90 ♦Salter and Schollenberger, 1939. Turk and Weidman (1945) give an average of 80, 80. and 90 per cent recovery for N, P, and K, respectively. tGilbertson et al. (1971). JPeterson et al. (1956/?). production, arc excreted as manure. Table 4 shows the recovery of nitrogen, phos- phorus, and potassium in some manures. The table shows that data from Salter and Schollenberger (1939) and Turk and Weidemann (1945) compare quite well with data from Gilbertson et al. (1971), even though much improvement in feed- conversion efficiencies has occurred since 1939. Distribution of nutrients in feces and urine Figure 4 shows relative distributions of nitrogen, phosphorus, potassium, and cal- cium excreted in horse, cattle, sheep, and swine feces and urine. Urine makes up less than 40 per cent of the total fresh weight of manure but is relatively more concentrated with respect to nitrogen and potassium than is the feces. Thus the nitro- gen and potassium contents of manure solids can vary considerably, depending upon the amount of admixed urine. Nitrogen excreted in animal feces con- sists of plant nitrogen that is resistant to animal digestion, microbial-cell protein synthesized from nitrogen available in the digestive tract, endogenous digested juices, and sloughed-off intestinal cells. Fecal ni- trogen closely corresponds to dry-matter nitrogen intake (Crampton and Harris, 1969). Urine contains some endogenous nitrogen resulting from small inefficiencies of the cycling of amino acids from one protein to another in the animal. This endogenous nitrogen loss is proportional to the metabolic-size of the animal (Asp- lund, 1971). When urea is fed to rumi- nants, some urea and some ammonia is absorbed by the rumen, filtered by the kidney, and lost in the urine ( Asplund. 1971). Most urinary nitrogen originates from the deamination of protein when pro- tein is used as a source of energy. The pro- portion of nitrogen excreted in the urine relative to that in the feces increases as the percentage of nitrogen in the ration is in- creased above the amount necessary for optimum growth. For example, if growing steers needing rations containing not more than 11 to 13 per cent protein are fed alfalfa hay containing 20 per cent crude protein, part of the protein will be metab- olized as an energy source — excess nitro- gen released by protein deamination will be excreted in the urine. Commercial live- stock feeders therefore seldom feed grow- ing animals more nitrogen than necessary for optimal conversion of v 'getable protein to animal protein. About 70 per cent of the nitrogen comes from the urine fraction of the mixture in poultry manure (White et al.. 1944). A relatively large proportion of the total nitrogen of fresh poultry-manure is in the form of uric acid, a water-insoluble material which appears visibly as the "white cap"on poultry droppings. Leibholz (1969) found about 39 per cent of the nitrogen as uric acid in one sample of poultry manure. Uric acid makes up about 13 SWINE SHEEP HORSE 100 , calcium" 44 *VW////y/ POTASSIUM 91.7 55.4 27.7 CATTLE 9 7.3 Fig. 4. Distribution of dry matter, nitrogen, phosphorus, potassium, and calcium in feces and urine of cattle, horse, sheep, and swine. Dry matter data from Salter and Schollenberger (1939); other data from Duley (1919) and Salter and Schollenberger (1939). 80 per cent of the nitrogen in poultry urine (O'Dell et ai, I960). Sodium, potassium, and chloride are mostly excreted from domestic livestock via the urine and form the majority of the salts in the fluid. Chloride alone can account for about 30 per cent of the salt in the urine of dairy cows (Adri- ano et al., 19716). Conversely, most of the waste calcium is resecreted into the lumen of the gut and passes out with the feces calcium would otherwise precipi- tate as kidney '-tones, which can be detri- mental to animal health. Magnesium is nol readily absorbed by ruminant animals and is excreted mainly in the feces. Phosphorus is excreted mostly in the feces in herbivores hut mostly in the urine o[ carnivores. Omnivores, such as swine and man, excrete significant amounts of phosphorus in both urine and feces. Of the commercially-raised animals, only swine have considerable phosphorus in their urine. Table 5 shows a comparison of the nu- trient composition of some animal feeds and the resultant fresh animal feces. The feces were urine-free, except of course for the poultry droppings. 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Nitrogen in the chicken manure was less than nitrogen in the origi- nal feed, which is not too unusual consider- ing that highly utilizable protein in rations for laying hens are transferred as egg pro- tein and that some volatilization of am- monia-nitrogen in the manure may occur quite rapidly after excretion. Sulfur and fiber concentrations in manures seem gen- erally dependent on animal digestion proc- esses and not as dependent on initial con- centration in the feed. It is also obvious that the sodium and potassium from the feeds were excreted mainly in the urine, since the concentrations of sodium and potassium were lower in the cattle feces, hut higher in the poultry manure sample, than they were in the respective feeds. Chemical composition of animal manures Table 6 summarizes chemical composi- tions of some animal manures, as reported in the literature. The age and degree of decomposition of manure, inclusions of bedding and soil, and amount of urine caught with the feces often modify the chemical compositions of manures and ob- scure the characteristics ascribable to fresh excreta from different species of animals. Values in table 6, therefore, can only represent the likely concentrations of nutrient elements in manures that must be used or removed. When nutrient concentrations of ma- nures are expressed on a fresh-weight basis, the moisture contents are the major source of variability between samples. Fig- ure 5 shows that pounds of nutrient per ton of manure decrease dramatically as moisture content increases. Characteristic digestion processes and feed preferences of different species of animals are responsible for some differ- ences in manure nutrient concentrations. Phosphorus in ruminant manures is gen- erally lower than in poultry or swine ma- nures because of the ability of ruminants to extract organically-bound phosphorus from plant feeds (Hays and Swenson. 1970) . As another example, steers, fryers, and growing animals receive more nitro- gen than dairy cows or laying hens. ( Beutel ct a!., no date ) . In the conversion of vegetable protein to animal protein, 17 Weight of manure 80 PER 60 CENT 40 MOISTURE Fig. 5. Effect of moisture content of manures on the percentage of dry matter, total weight, and water loss from manures (data of D. Bell, 1971). meat protein production is relatively less efficient than milk or egg protein produc- tion. The protein conversion ratio for well- managed feedlot cattle is approximately 8 to 1. The ratio for a commercial dairy cow throughout its 6-year commercially- productive life is about 4 to 1, and ap- proaches an amazing 1.1-1.4 to 1 during the prime years of her life if she is fed rations balanced to achieve optimal protein conversion. Vegetable protein not con- verted to animal protein will be excreted. The percentage of nitrogen in steer ma- nures is therefore usually higher than in manures from dairy cows; the nitrogen in broiler manures is generally higher than in manures from laying hens. The gains of more mature animals consist of more fat and less protein than those of young growing stock. The current con- sumer demand for fat and marbling in red meal has encouraged inefficient use of vegetable proteins during the last few weeks of finishing. Use of protein anabolic compounds, sucb as diethylstilbestrol (DES), can generally increase feed- to body-weight conversion rates, With such growth regulators, the rate of gain of castrated animals is similar to the natural growth rate advantage of uncastrated male animals. The percentage of protein, bone, and water in the carcass is increased by hormone treatment while the percentage of fat is decreased. Nitro- gen, calcium, and phosphorus retention is increased by the use of hormones (White- hair et al, 1953), and less nitrogen is ex- creted in the feces and urine (Clegg and Cole, 1954). Daily excretion of nitrogen in the manure of rapidly growing cattle is slightly higher than that of slower growing cattle, but more protein is wasted over the longer feeding period associated with poor conversions (Pfander, W. H., 1971. Un- published data). McDonald et al. (1973) report an estimated 25 per cent increase in weight-gain of beef cattle in response to hexestrol treatment in the United King- dom. Hormone treatments of meat-animals can increase the efficiencies of vegetable protein to animal protein conversions and can therefore decrease the amounts of an- imal manures produced per unit of an- imal protein created, thus changing the composition of animal manures through improved nitrogen utilization. However, intentional uses of hormone supplements have raised controversial health, safety, en- 18 vironmental, and legal issues that have been resolved temporarily by banning the use of diethylstilbestrol as a feed additive. Sodium and total salt contents of animal manures seem to vary with region and ani- mal management. In the arid southwestern U. S., salt in water and forages makes the salt content of these manures higher than those of most other regions of the U. S. Salt concentrations in manures in southern California often range between 5 and 10 per cent of the dry weight of the manure. Morris and Gartner (1971) estimate the sodium requirement of growing steers to be 3.1 grams per day. In some areas, cattle receive several times more than that from available feed and water, but feeders may still add sodium chloride to the ration on the general assumption that some benefit may result from the practice. Sodium chloride is sometimes added as a diuretic. The need for large quantities of egg- shell calcium by laying hens is the reason for the high calcium salt content in rations and in hen manure. Alterations of mineral composition of manures during storage Handling and storage of manure greatly influences redistribution of the excreted nutrients. The nutrient content of com- posted or aged manure is not comparable to that of fresh manure because nutrient ratios of the final product are influenced by losses of nitrogen by volatilization and losses of nitrogen and other nutrients by leaching (see pages 27-28). For example, the nitrogen-to-phosphorus ratio of fresh chicken manure is generally higher than 2.5, but the loss of nitrogen from manure during aging results in the somewhat lower nitrogen-to-phosphorus ratios of older ma- nures. Bedding or litter is relatively low in nu- trients and will dilute nutrient and ash concentrations of the manure. However, bedding or built-up manure will conserve urinary nutrients that would otherwise be lost. Nutrient contents of corral manures vary with stocking density and age of the lot. Heavy stocking of new corrals promotes the mixing of manure with the soil so that wastes scraped from the corral often in- clude generous proportions of total ash, zinc, silicon, aluminum, iron, and other minerals characteristically abundant in soils. Once a manure pack is built up, how- ever, mixing of manure and soil is mini- mized and less soil material is removed from the lot. Gilbertson et al. ( 1971 ) found greater concentrations of sodium, calcium, and manganese, and smaller concentrations of nitrogen, potassium, magnesium, zinc, and iron in manure removed from densely- stocked beef-cattle feedlots as compared with others having fewer cattle per lot. Nutrients excreted per production cycle Animal production is a dynamic process in which an animal is expected to contrib- ute productively, preferably throughout the year. Beef cattle gain 2 to 2.5 pounds per day; a dairy cow's milk-production cycle includes a dry period, calving, and then continues with a predictably varying rate of milk production. During growth cycles the feed ration is varied as the animal's metabolism rate changes, thus causing ma- nure dry matter and nutrient output to change quantitatively and qualitatively. Therefore, the amounts of manure nutri- ents deposited on the farm are connected directly with the dynamic life of the ani- mals, as well as to their species and num- bers. Table 7 gives measurements of the total amount of nitrogen, phosphorus, and potassium in one production cycle for dif- ferent species of farm animals. The values for nutrient elements in ex- crements from laying hens presented in table 7 generally agree with the 159, 55, and 57 pounds of nitrogen, phosphorus, and potassium per 100 bird-years, respec- tively, calculated from data of Taiganides and Stroshine (1971). Calculations from those authors' data for a large dairy cow show more nitrogen ( 195 pounds per cow- year), slightly less phosphorus (23 pounds per cow-year), and less potassium (81 pounds per cow-year) than those reported by Webber et al. (1968) in table 7. The average yearly nitrogen excretion by cows in the Chino-Corona dairy area in southern California is estimated by Adriano et al. (19716) to be 146 pounds per cow-year, remarkably similar to that reported by Webber et al. (1968). The estimate of yearly manurial nitrogen from feedlot steers (table 7) is somewhat smaller than the 100 pounds per animal-year estimated by Pfander (1971, unpublished data) but 19 Table 7 QUANTITY OF NUTRIENT ELEMENTS EXCRETED IN MANURE OF VARIOUS ANIMALS DURING THEIR PRODUCTION CYCLES* Number and type of animal, length of production period, and animal weight during production period Amount of element excreted One thousand broilers; 10 weeks; to 4 pounds (0 to 1.8 kg) . . One hundred hens; 365 days: 5 pounds (2.3 kg) . . . Ten hogs; 175 days; 30 to 200 pounds ( 14 to 91 kg) Two beef; 365 days; 400 to 1 100 pounds (181 to 500 kg) One dairy cow; 365 days; 1200 pounds (544 kg). lb. 155 125 115 140 140 kg 70 57 52 64 64 lb. 31 44 29 29 kg 14 20 13 13 13 lb. 50 46 33 145 145 kg 23 19 15 66 66 'From Webber et al. (1968). much more likely that the 200 to 240 from data of Taiganides and Stroshine pounds per animal that can be calculated (1971). PHYSICAL PROPERTIES OF ANIMAL MANURES The relative paucity of data about physical characteristics of animal manures repre- sents a long period of neglect of the actual importance of these properties. Relevant physical data have been generated only re- cently in response to a recognized need for improved manure-handling machinery and new methods for reducing costs of treat- ment, storage, and disposal. Design of ef- fective storage and treatment facilities re- lies on good data describing solids, par- ticle-size distributions, density, and liquid properties of manures. The scarcity of basic information about physical prop- erties could explain the limitations of some designs which appear to have been based on assumptions that manures are homogenous mixtures having little varia- tion with time or between species of ani- mals. Volatile* and fixed solids Volatile and fixed solids are two fractions of the dry matter in animal manures. W hen a small amount of dry manure is ignited In a laboratory muffle-furnace at a giVen temperature (550 000 C I the volatile solids lost during combustion are an approximation of the organic matter in the manure. The inert residue remaining after combustion is referred to as "fixed- solids" or, more commonly, "ash," and represents the mineral portion of manures. Sobel (1966) estimated the ash of chicken manure to be 24 per cent of the total solids and that of dairy feces to be 10 per cent. (Some other values are given in table 6) . Recent studies of several California ma- nures (Hafez et al., 1974) estimate the ash in fresh chicken manure to be about 32 per cent, and that in fresh dairy and beef feces to be 15 to 18 per cent. Ash content of chicken manure was thought to be generally higher than that of rumi- nant or swine manures because of the considerable amount of grit in the poul- try diet, and the relatively low fiber and high salt content of the highly-digestible poultry rations. Undigested fibrous resi- dues of ruminant manures contained only about 8 per cent ash. Dilution of the fresh manures with the usual types of bedding Or litter reduced ash contents. Ash con tents of composted manures were consid- 20 erably higher (40 to 50 per cent ash in some samples), and in one sample of com- posted corral scrapings the ash was as high as 70 per cent of the dry matter. Particle-size distributions Particle-size distributions of fresh manure depend both upon the ration and digestion processes of the animal. Sobel (1966) found that dairy manure had a lesser pro- portion of fine particles and a greater con- tent of coarse particles than did chicken manure (fig 6). Research by the Uni- versity of California Agricultural Experi- ment Station (Hafez et al., 1974) sug- gests that the difference between chicken and ruminant manure is most evident in the very coarse particles (greater than 2 millimeter in effective diameter as determined by wet-sieving) . When par- ticles are wet-sieved their "effective di- ameters" are assumed to be less than sieve- hole size if the particles pass through the sieve. A series of sieves separates the ma- terial into a particle-size range. Coarse particles generally represented less than 5 per cent of the chicken manure and con- sisted mostly of feathers and grit. In rumi- nant manures, however, 11 to 18 per cent of the dry matter was in the coarse par- ticle-size range. These large organic par- ticles were generally undigested feed res- dues of a fibrous nature. Addition of fibrous bedding or litter increases the rela- tive proportion of coarse particles in col- lected manure (Hafez et al., 1974). Realization of the fibrous nature of the numerous large particles in cattle manure has led to several successful efforts of sep- aration and re-use of these fractions (Fair- bank and Bramhall, 1968; Graves et al., 2 10 5 ARTICLE DIAMETEf Fig. 6. Particle size distribution of fresh chicken and dairy cow manure (from Sobel, 1966). 1971; Anon., 1973). These fibrous par- ticles can be recycled as animal bedding, among other uses, with a concurrent re- duction in the volume of material to be handled and disposed (Bramhall, 1970) and simplification of wastewater disposal. Particle density and bulk density Particle density and bulk density are ex- pressions of weight-to-volume ratios useful in the design of storage and handling systems. Particle-density data refer to the average density of various particles in animal manure. Sobel (1966) found the average particle density of chicken manure to be 1.80 grams per cubic centimeter, and that of dairy feces to be 1.44 grams per cubic centimeter. Hafez et al. (1974) found that the particle density of vari- ous fresh manures ranged from 0.97 to 1.76 grams per cubic centimeter. The higher density values for poultry manure reflected the higher ash content, includ- ing grit, in the poultry diet. Some min- eral calcium constituents in the diet of laying hens have a particle density of 2.0 grams per cubic centimeter (Sobel, 1966) . Older manure contains a higher propor- tion of mineral constituents (ash), and should have a high average particle den- sity because of bio-oxidative losses of or- ganic matter having a density of 1 or less. Measurements of bulk density of dry or moist animal manures include the pore space as well as the densities of their min- eral and organic particulates in the final value. At moisture contents above satura- tion when the pore-void space is filled with water, bulk density of the moisture can be calculated by adding the average particle density of the manure and the density of water (Sobel, 1966). Figure 7 shows ac- tual and calculated bulk densities of chicken and dairy manure at high mois- ture contents. The maximum density of manure slurries is somewhat greater than that of water, 62 pounds per cubic foot for dairy-manure slurry and 65 pounds per cubic foot for chicken-manure slurry (Hart, 1960). The bulk density of samples dried and ground as species-typical manures ranged from 0.20 grams per cubic centimeter (horse manure) to 0.58 grams per cubic centimeter (chicken) in one experiment (Hafez et al., 1974). With compression 21 - " Chicken •>^\ - Dairy Com •/ / TOTAL BULK DENSITY WET BULK DENSITY MOISTURE CONTENT -per cent wet Fig. 7. Bulk densities of chicken and dairy-cow manures at high moisture contents. Straight lines indicate respective particle densities (from Sobel, 1966). of these samples at pressures up to 20,000 pounds per square inch, the bulk den- sity was increased 4 to 8 times the orig- inal value to values greater than the original particle density (fig. 8) . Compres- sion of the individual flexible particles as well as compaction of the particles together were thought to have given these high values. Optimum moisture content for maximizing the bulk density of ground manures at moderate pressures (up to 5,000 pounds per square inch) appeared to be about 15 to 17 per cent. The principal suggestion that has come from these studies of compression charac- 2 5 2 ^ 1 5 1 A Chicken jUI o Dairy 5 n -I a 1 L. J. 1 1 Swine . ... i . 5000 10000 PRESSURE - lb Fig. 8. Bulk densities of air-dry chicken, dairy, and swine manures as functions of pressure (from Hafez etal., 1974). y* — N. Maximum \ by Procto compact ion r test Minimum compaction \ - by light pressing \ Maximum compaction^^ — y y y y y y y y y S 1 1 1 1 1 ~T \ Mini mu m compact ion ^ 20 40 60 80 TOTAL SOLI DS - per cent Fig 9. Change in bulk density of chicken ma- nure during compaction at various moisture con- tents (from Hart, 1963). teristics is that relatively dry animal ma- nures of any type can be readily pelletized into blocks or cylinders. No additional binding agents are required, and included straw and bedding materials do not de- tract from the desirable physical state when compressed. The pelletized products are hard, stable, dust-free, and essentially odor-free materials having a bulk density greater than 1. These pellets can be pre- served for as long as they do not come into contact with moisture. The expense of pelleting may currently be a strong deter- rent for most practical circumstances of handling, but if manures are used as fuels and feeds in the future, pelleting may be- come worthwhile. Compaction of manures with higher moisture percentages are shown in figures 9 and 10. The bulk density of manure de- creases rapidly as moisture is removed from the manure. Surbrook et al. (1971) . : — " ^<^CHICKEn\ \ SWINE X \\ - 04/ffr\ \\ \ s 20 40 60 TOTAL SOL IDS IN MANURE 80 sercer 10. Maximum compaction of chicken, and swine manures; data obtained by Fig. dairy, using the Proctor test, ASTM No. D558 (from Hart, 1964). 22 found a reduction of the bulk density of poultry manure from about 60 to from 12 to 20 pounds per cubic foot with high-tem- perature drying. More data on the effects of moisure and compaction on the bulk densities of various manures would be use- ful in designing systems for efficient han- dling of solid manures. Flowability Flowability of manures affects the ease of pumping and hydraulic transport. Sobel (1966) correlated moisture contents of manures with their flow characteristics, and concluded that less additional water was necessary to liquify dairy manure than chicken manure (fig. 11) and that dairy manure lends itself more easily to liquid handling. Figures 12 and 13 also give flow comparisons of fresh manures at different moisture levels; figure 13 gives consistency reference points in terms of commonly understood mixtures such as batters and pickle relish. Although special pumps have been de- veloped for pumping manure slurries (sus- pensions in water) having 20 per cent or more suspended solids, equipment prob- lems and costs are reduced if the solids content is reduced below 20 per cent. Staley et al. (1971) recommended not more than 8 per cent solids in dairy ma- nure slurries, and Hart et al. (1966) advocated not more than 4 per cent ma- nure solids as a compromise between ex- cessive volume and pumpability. There is an increased tendency for manure par- ticles to settle from more dilute slurries (Sobel, 1966), thus requiring mixing to maintain a uniform solids-content while being transferred by pumping. For detailed analysis of flow properties of manure and further technical informa- tion, the reader is referred to articles by Taiganides et al. (1964), Hart et al. (1966), and Staley et al. (1971). Here, it is sufficient to say that manure slurries can be pumped and transported hydraulically with commercially available equipment. The decision to convert to liquid systems is not limited or dictated by flow data alone but also by other considerations of disposal, nuisances, climate, pollution, and economics. Water-holding capacity Water-holding capacities of manures in corrals affect runoff events following pre- cipitation. Hafez et al. I 1974) used stand- ard pressure-plate methods that are ap- plied to soils to measure moisture-holding capacity of various previously-dried ma- nures at V^-atmosphere suction-tension. The moisture capacities ranged from 101 per cent to 406 per cent of the wet ma- nure, with generally higher values re- ported for fresh fibrous ruminant ma- nures. Poultry manure, composted ma- nures, and those mixed with soil (e.g., cor- ral scrapings) held less water. Measurements of water-holding capacity of manures in the field is complicated by slow, variable wetting characteristics of dry organic materials, ambient moisture- tensions other than V3- atmos pbere, and channeling of water through unsaturated manure. Keeton et al. ( 1970 ) measured the moisture content of feedlot manures in columns after wettings by simulated storm conditions. Moisture contents of the ma- nures ranged from 59.1 to 62.2 per cent. In a similar experiment with natural and simulated rainstorm conditions, Hafez et al. (1974) found that the water would move to lower layers of the manure before wetting the top layer to capacity. The freely-drained water-holding capacity of the surface layer of manure exposed to natural rain was 62.3 per cent on a wet- weight basis. Rates of water infiltration into corral surfaces influence the moisture capacity of the surface layers of manure and therefore the runoff potentials, but studies have not included measurements of infiltration rates on packed corral surfaces. Both loose and compressed manures swell rapidly when exposed to liquid water. For example, pelleted animal manures swelled from two to five times their orig- inal volumes when exposed to a free water surface on one edge (Hafez et al., 1974). The swelling of the pellets was correlated (r = 0.79) with the water-holding capac- ity of the manure. Pellets of fibrous ma- nures (e.g., dairy) absorbed water faster and in larger amounts than did pellets of the more granular manures (e.g.. chicken) . Total water absorbed ranged from 1.85 to 3.49 milliliters per gram of manure. Manures can be handled easily as solids in loose or compressed forms. When han- dled as liquids, due consideration should be given to differences in particle-size characteristics, densities, and settling rates between various types of manure. 23 < £ a. ^ a: z uj < a 2 Q UJ X Q (/) Q Ld < tr 5 - 4 - < u. Q °] in o < ^ CL O U. 3 - 80 85 90 CHICKEN 95 975 85 90 95 97.5 DAIRY COW (per cent moisture) Fig. 1 1. Moisture contents versus fluidity of diluted fresh manures (from Sobel, 1966). Chicken PER CENT SOLIDS 5 10 15 20 25 30 TOTAL SOLIDS IN MANURE - percent Fig. 12. Flow comparison of chicken, dairy, and swine manures based on the slump test de- veloped for testing concrete (from Hart, 1964). 1 . 5 .i.l.i 10 15 , . 1 .... 1 , 20 . . . 1 . 25 , , . 1 P U LT RY 1 1 1 5 , , 1 , 1 , 10 15 1 . . . 1 , i 20 , , 1 , 25 ..,1. SWINE 1 1 2 4 1,1. 6 8 1 . 1 10 1 12 1 . DAI RY t ater t hal f and half, cream t t butter- pancake milk batter t coc ktai 1 dip t pickle relish Fig. 13. Comparative consistency of poultry, swine, and dairy manures at various solids con- tent (from HartetaL 1966). 24 DECOMPOSITION OF ANIMAL MANURES Animal digestion and decomposition processes Domestic animals raised commercially for consumption dispose of initial food energy as metabolic energy, energy stored in the carcass, and energy that passes on as waste. By-products of the feeds supplying animals with energy appear as waste in the forms of heat, simple inorganic com- pounds in solution, gases, and unassimi- Pl G Co Re An FOWL Re CI COW Re An Fig. 14. Diagrammatic representation of the digestive tracts of swine, fowl, and cow. An = Anus. Ab = Abomasum. Ca = Caecum. CI = Cloaca. Co = Colon. Cr = Crop. D = Duodenum. G = Gizzard. I = Ileum. Oe = Oesophagus. Om = Omasum. P = Proventriculus. Re = Rectum. Rt = Reticulum. Ru = Rumen. S = Stomach. (From Mc- Donald et al., 1973). lated inorganic and organic solids in ma- nurial excretions. Domestic and feral (wild) animals can be classified into three groups on the basis of their inherited, primary dietary prefer- ences or habits. Carnivores, including the dog, the cat (and the falcon, among avian species), obtain their energy by consum- ing flesh of other animals. Herbivores pri- marily eat plant material, and omnivores consume both meat and plants in varying quantities. The feral pig evolved as an omnivore and has developed a digestive system that is quite similar to that of hu- mans. The three groups of animals digest their food differently and the resultant ma- nures are quite distinctively different. Of the three, the digestive system of the carni- vore is relatively small. The carnivore's digestive system is well-adapted to enzy- matic action on animal flesh, and micro- bial action is minimal although some putrefactive organisms are present in the large intestine. Feces of carnivorous an- imals are relatively small in quantity but odorous. The commercial domestic animal popu- lation in California is essentially herbivor- ous. Ruminant herbivores such as cattle, goats, and sheep have a specialized lumen (the rumen) adapted for fermentative pre- digestion by microorganisms (fig. 14). These microorganisms invade the rumen shortly after birth and thereafter digest 70 to 85 per cent of the dry matter consumed by the animal (Bryant, 1970) . Plant food- stuffs easily digestible by microorganisms are rapidly converted to volatile fatty acids, and these important energy sources for the ruminant animal are readily ab- sorbed. Microorganisms growing in the ru- men also synthesize microbial protein from plant proteins and from inorganic nitrogen sources such as urea. These reconstituted proteins and certain microbially synthe- sized vitamins are made available to the animal as the microbial mass passes to the abomasum, the acid-secreting true stomach where the microorganisms are digested. Further absorption of digested food mate- rials takes place in the abomasum and in- testine; the residual mass undergoes fur- ther limited fermentation in the large in- testine before excretion. Non- ruminant, herbivorous animals, such as the horse and the domesticated pig, 25 make use of hydrolytic enzymes to decom- pose starches and proteins in the upper di- gestive tract. Considerable fermentative digestion takes place in the large intestine, but it is not known how much of these latter products of fermentation are avail- able to the animal. Microbial protein syn- thesized this far down in the digestive tract is not available to these animals and is passed out in their feces. The digestive system of herbivores is larger and longer than that of carnivores, but the proportion of feed excreted in the feces is also relatively larger because of the poor digestibility of resistant ligna- ceous plant fibers and of the proteins and starches protected by these fibers. Up to 25 per cent of cattle feces can consist of humus-like lignoproteins (Grub et al., 1969a, b) . Under ordinary feeding prac- tices another 20 to 30 per cent of cattle feces are microbial cells and undigested food (Loehr, 1969). The avian digestive system is distin- guished by the presence of a crop and a gizzard. The crop is merely a storage and food-softening organ, but the gizzard is re- sponsible for the fine-ground nature of avian feces. Feed digestibility of seed- eaters is enhanced by seed pulverization taking place in the gizzard. There is some evidence of limited fermentation of eellu- losic materials in the ceca of birds (Stur- kie, 1970). Modern animal rations are selected from plant materials containing the highest quantities of substances most vulnerable to decomposition. The digestibility of these rations often ranges from 70 to 80 per cent. Almost all of the sugars and a considerable portion of the proteins, starches, and fats in the original animal ration are metabo- lized by the animal with the help of the adventitious intestinal microorganisms. The fecal wastes consist of only the more resistant materials of the original ration (e.g., hemicelluloses and lignins) and those formed in the digestive tract U'-g-, lignoproteins). In addition, other mate- rials formed too far down in the digestive system to be digested and absorbed, such as digestive juices, sloughed intestinal cells and muCOUS, and some microbial cells. are also excreted ill the feces. Domestic animal digestion processes, es- pecially those of ruminants, parallel the de- composition of fecal residues; the differ- ences can be expressed in terms of rates. The nature of further decomposition proc- esses in manure after excretion reflects the partially decomposed character of the fe- ces. Much of the manure will be only slowly biodegradable. Decomposition processes The scheme of nature demands that all organic substances from living organisms be decomposed eventually into elements or simple compounds and redistributed in the biosphere, and nature has provided the organisms and biochemical processes to fulfill this cycle. Bacteria, protozoa, fungi, actinomycetes, worms, and insects attack manure as it is excreted as waste from the animal. Degradation and decom- position processes continue until manure is returned to gaseous carbon and nitrogen compounds, minerals, and water. The rates of decomposition of various constituents in manure vary with the diversity of food, temperature, water, oxygen, and other en- vironmental conditions, but the process of decomposition remains dynamic and con- tinuing. The ability of the microbial population to decompose organic waste is predicated on a population complexity. The popula- tion is continually reformed by natural and artificial modifications of the micro- environment. Decomposition of manure in piles, waters, or soils involves three steps: rapid decomposition, synthesis of microbial pro- toplasm, and formation of new compounds by condensation and polymerization (Waksman, 1952). These steps are indis- creet and overlapping in natural systems, and the three will repeat several times in the decomposition process as synthesized microbial bodies are attacked by others and, in turn, are decomposed. As decomposition proceeds, the various organic constituents of the substrate are attacked at different rates. Starches, hemi- celluloses (long chains of linked hexose or pentose sugars), cellulose (long chains of linked glucose sugar), and proteins are de- composed quite rapidly as numerous or- ganisms use the carbon in these materials as an energy source. Only a few aerobic species are capable of decomposing the more resistant lignins and fats (Waksman and Starkey, 1931). These latter materials will remain intact much longer and thus accumulate in the residual, nondescript, decomposing mass. 26 The microroganisms will synthesize some of the mineralized decomposition products of manure into their own proto- plasm. End products of organic matter degradation are voided to the geosphere with an over-all loss of the original mate- rial. Subsequent polymerization reactions that take place in soils and cooling com- posts (Poincelot, 1972) include the pro- duction of complex lignoproteins called "humus." The oxygen status under which manure is decomposed will determine the nature of the decomposition processes more than any other single factor. Completeness and rapidity of decomposition of manures is determined by oxygen supplies since oxy- gen is utilized in oxidative microbial meta- bolic processes that terminate in end prod- ucts of carbon dioxide and water. The oxi- dative energy transformations of rapidly metabolizing microbial cells are responsi- ble for the heat generated in aerobic com- posts, soils, and waters. Anaerobic decomposition (fermenta- tion) is quite different. 3 Because lack of oxygen excludes the efficient fungi and actinomycetes, anaerobic digestion by spe- cialized bacteria is slower and less efficient. During anaerobic decomposition of or- ganic compounds there is an accumulation of compounds which normally require oxy- gen for further breakdown. These residual compounds include alcohols and organic acids from the decomposition of carbohy- drates, and pyridines, indoles, skatoles, ammonia, and amines from the breakdown of proteins. Instead of oxygen, organic compounds can be used as the hydrogen acceptors in metabolic processes of some anaerobic bacteria. Methane, hydrogen, and carbon dioxide gases are high-energy- containing compounds which can be set free during fermentation. The remaining organic residuals still have a high energy content. The oxidative processes of mineraliza- tion of organic nitrogen to ammonia, and the subsequent fate of ionic inorganic ni- trogenous products, is of special signifi- cance as ammonium- and nitrate-nitrogen are utilized by plants. Hydrolysis of nitro- gen-containing proteins in manure will yield polypeptides, amino acids, and some ammonia. Further oxidation of the remain- ing organic nitrogen compounds will re- lease more ammonia. In addition, the rapid hydrolysis of urea by ubiquitous urea-de- composing enzymes will also yield am- monia. In poultry manure, nitrogen is mainly in the form of uric acid. Common uric acid decomposers indigenous to poul- try feces perform the chain of oxidative- hydrolysis reactions necessary to convert uric acid to urea (SchefTerle, 19656). A few can even convert uric acid directly to ammonia. Ammonia is the common source of ni- trogen used in the synthesis of microbial protoplasm. Ammonia will be assimilated along with carbon energy sources at defi- nite ratios that are dependent upon spe- cific microorganisms. For example, fungi require less nitrogen than bacteria. As a whole, microbial populations assimilate all of the nitrogen from substrates having car- bon (C) and nitrogen (N) in the weight ratio of C:Nr:30:l (Poincelot, 1972). If the C :N ratio of an organic substrate is less than 30, some ammonia will be liberated as a result of continuing microbial activities. If decomposable material having a C:N ra- tio higher than 30 (such as manure con- taining large amounts of straw) is applied to soil, microorganisms will draw mainly upon mineral nitrogen in the soil at the expense of growing plants. Carbon is res- pired and lost from the system as car- bon dioxide during microbial metabolism. As a result, the carbon-nitrogen ratio of the residual organic matter will approach a ratio of C:N=10:1, which is the C:N ratio of microbial protoplasm. Nitrogen biologically immobilized temporarily in microbial cells will eventually be released as ammonia when the nitrogen supplies exceed the nitrogen demand of living mi- croorganisms dependent on dwindling car- bon and energy sources. The length of delay of ammonia release depends on the initial carbon :nitrogen ratio, and on sub- sequent environmental conditions and food supplies that influence rates of microbial growth. Ammonia and carbon dioxide form un- stable chemical compounds [(NH 4 ) 2 COs 8 Aerobic organisms including all higher life forms and many microorganisms are restricted to oxygen-linked biological reactions, whereas the anaerobes or fermenting microorganisms grow in the complete absence of oxygen. Faculative anaerobes possess both aerobic and anaerobic life systems. Fermentation means "life without air." Putrefaction is the result of fermentative decomposi- tion of protein that gives rise to foul-smelling amines. In the presence of oxygen, however, these unpleasant, odorous amines are oxidized by aerobes with the release of ammonia. 27 and NH4HCO3] which dissociate readily into gaseous ammonia and carbon dioxide. Volatilization of ammonia gas (NH 3 ) is fa- vored by the normally warm, alkaline, dry- ing conditions of voided manure, whereas acidic conditions shift ammonia into the stable ionic form of ammonium (NHj). Volatile ammonia gas will tend to be cap- tured by surrounding media which are acid or less alkaline, thus increasing the pH of the capturing medium. Volatiliza- tion of ammonia from the decomposition of uric acid in poultry manure is probably responsible for the increase in the pH of poultry house litter during warm weather (Schefferle, 1965a). Sheep urine voided on pastures may lose 12 per cent of the ni- trogen as gaseous ammonia and induce a concurrent upward shift in soil pH within a few hours (Doak, 1952). Beef cattle feedlots and dry-lot dairies continuously release significant amounts of ammonia into the atmosphere (Hutchinson and Viets, 1969; Elliott et al, 1971; Luebs et al, 1973). Under aerobic conditions of soil systems, ammonium-nitrogen per se is utilized as a source of energy by Nitrosomonas micro- organisms, which release nitrite (NO2) as the oxidized byproduct. Other species de- rive energy from biological oxidation of nitrite (NOT) ions to nitrate (NO") ions. As only small amounts of energy can be derived from the oxidation of nitrite to ni- trate, the turnover rate of this conversion is rapid. As a result of the activity of these organisms, nitrate is the final nitrogenous end product of aerobic manure decomposi- tion. Where oxygen is limiting, certain micro- organisms use oxygen from the nitrate molecule as a hydrogen acceptor and denitrify nitrate to nitrogen or nitrous oxide gases. Denitrification results in a net loss of nitrogen to the atmosphere, and will lower the nitrate content of any mate- rial where oxygen is limiting and carbona- ceous food for microorganisms is sufficient. The presence of large amounts of ma- nure in a pile or in soils creates corre- spondingly large demands for oxygen as the microorganisms utilize available oxy- gen in decomposition processes. Restric tiona upon air movement through tli"' organic matter will create an environment of anaerobiosis. Large-scale anaerobic en- vironments are common in flooded soils and compacl wet manure heaps or on ma- nured surfaces, whereas aerobic conditions predominate in well-drained soils and loose manure heaps. Table 8 shows compara- tive products of manure decomposition for aerobic and anaerobic environments. Un- fortunately for anyone trying to predict or explain decomposition processes, the oxy- gen status in soils, manure piles, or waters is seldom strictly anaerobic or aerobic over any reasonable distance. The surface of a moist compost heap or soil may be well- aerated while the interior may have very little oxygen. Completely different micro- bial populations would exist at each ex- treme, with gradations of population com- position in between. Not only would dif- ferent products result at each different microenvironment, but these products would migrate toward other sections by volatilization, leaching, capillary-tension and diffusion processes. The end products of one section would be subject to bio- logical activities in other sections. Anal- ogous gradations can exist in manured waters where algal activity and turbulent flow phenomena may carry oxygen into otherwise anaerobic environments. Mixing of end products in water bodies would be greater than in porous media such as soils. Amounts of aeration are often indicated by the oxidation-reduction (redox) poten- tial of a medium. More positive redox values indicate better aeration. Nitrate will be denitrified at redox values (E h ) less than about +225 millivolts whereas sul- fate will be reduced at lower values (-363 millivolts) . Methane will be produced only at very low redox values (Elliott and McCalla, 1972). Nitrate that is formed in the aerobic surface layers of manure ponds or compost heaps and migrates to an anaerobic horizon will be denitrified and lost from the system. Conversely, alcohols, organic acids, and odorous nitrogen com- pounds produced in anaerobic interiors of clumps or piles of organic matter can be oxidized at the aerobic surface. Changes in manure during decomposition The profound quantitative and qualitative transformations taking place during de- composition or composting of manures result in entirely different product char- acteristics than those of the original waste. Changes in physical structure and mineral composition affect subsequent values and 28 Table 8 GENERALIZED PRESENTATION OE END PRODUCTS OF MANURES DECOMPOSED UNDER AEROBIC AND ANAEROBIC CONDITIONS Aerobic decomposition Anaerobic decomposition Carbon compounds Nitrogen compounds Phosphorus compounds Sulfur compounds Carbon compounds Nitrogen compounds Phosphorus compounds Sulfur compounds end products end products co 2 NO, H 2 P0 4 so 4 C0 2 ,CH 4 N 2 , NH, H 2 P0 4 S Microbial cells Organic acids Alcohols Microbial cells Pyridines Indoles Skatoles Amines Mercaptans H 2 S 'From McCallap/cr/. (1970). use. Materials lost from the waste can af- fect the quality of surrounding soil, air, and water. The weight and volume of the original mass of organic matter decreases as meta- bolic gases are liberated. McCalla et at. (1970) estimated that more than 75 per cent of the organic matter from manure added to soils decomposes within 1 year. In another study, piles of moist dairy-cow manure lost an average of 59 per cent of their dry matter, and the volume was re- duced from 9 to 44 per cent during the process of composting (Willson, 1971). Wells et al. (1969) found that aerobic composts of manure from silage-fed beef lost 20 per cent dry matter and 40 per cent volume in 10 days during conditions ideal for decomposition. Decomposition residues contain most of the original ash and a high proportion of the original lignin. Percentages of these two will be higher in the residue because of proportional decrease of companion ma- terials more susceptible to decomposition. Table 9 illustrates the relative change in the chemical structure of manure that can occur during decomposition. The slowly- decomposable lignins and lignoproteins be- come part of the soil humus and continue to decompose at rates proportional to the remainder present. The half-life may be a decade or more but as decomposition proceeds further, the residues become even more resistant, finally releasing about 1 per cent of the remaining residue each year. The decomposition of organic wastes under anaerobic conditions is much slower. as peat deposits of former shallow lakes and marshes testify. Decomposable organic matter is lost from anaerobic systems when bacteria which are highly-sensitive to oxy- gen convert organic intermediates to meth- ane gas or carbon dioxide. The biochemical oxygen demand (BOD) and chemical oxygen demand (COD) tests have been applied to liquid farm wastes in order to estimate roughly the decomposable organic matter in ani- mal manures. 4 The BOD test provides an estimate of readily oxidizable material ex- pressed and the oxygen required by stan- dard microorganisms for the decomposi- tion of a given amount of material over a specified length of time, usually 5 days. The COD test utilizes a strong chemical oxidant to evaluate total decomposable * Sanitary engineers speak of the BOD (biochemical oxygen demand, or biological oxygen demand) of an organic infusion as the oxygen used in meeting the metabolic needs of aerobic microorganisms in water rich in organic matter. The amount of oxygen dissolved in pure water equilibrated with the atmosphere is only about 8 parts per million. This is enough oxygen to oxidize 15 parts per million of a carbohydrate such as sugar or starch. Therefore, the BOD of 15 parts per million of an easily metabolized organic compound is sufficient to remove dissolved oxygen from the water. Actual levels of oxygen at any given time will depend upon rates of oxidation by microorganisms and rates of restoring oxygen by contact between the water and overlying atmosphere. 29 Tablh 9 CHANGES IN THE COMPOSITION OF ANIMAL MANURES DURING DECOMPOSITION* Sheep manuret Horse manure^ Chemical constituent Fresh manure Manure decomposed for 192 days Fresh manure Manure decomposed for 290 days Ether-soluble substances Water-soluble substances Hemicelluloses Cellulose 2.83 24.92 18.46 18.72 20.68 17.21 per cent, dry-w 2.58 17.89 7.31 12.79 27.31 19.23 eight basis 1.89 5.58 23.52 27.46 14.23 6.81 9.11 0.95 5.71 12.67 5.97 Li tin in 28.43 Crude protein 16.38 Ash 19.32 ♦From Waksman and Starkey (1931). ^Includes mixed solid and liquid excreta. + Solid excreta only. organic matter (McCalla et al., 1970) . One objection to drawing many conclusions about the pollution potential of animal wastes solely from data generated by the BOD tests is that the 5-day BOD test is supposed to represent 80 per cent of the total BOD, whereas this figure seldom ex- ceeds 60 per cent with animal manures (Taiganides and Stroshine, 1971). The two tests are suitable however, for direct comparisons of manures from different types of animals and treatment systems. Cellulosic rations of grass-eating animals such as horses, sheep, or cattle give their manures relatively lower BOD values than manures from poultry or swine. (Table 10 gives representative values for BOD and COD of different animal wastes.) The BOD of animal manures has been related to that of human sewage (popula- tion equivalent, or PE). The BOD of the human excrement is approximately 0.12 pounds per capita-day and that of human sewage is currently about 0.20 pounds per capita-day (Taiganides and Hazen, 1966) . Population equivalent should not be con- strued to mean "pollution equivalent," as only a small percentage of animal manures reach surface waters. However, the BOD of corral runoff is at least an order of magnitude greater than that of municipal sewage (Grub et al., ]9G9a,b) and can be as much as 100 times greater (Law and Bernard, 1970). Because animal and hu- man wastes exert a substantial oxygen de- mand on receiving waters, manures should not be introduced indiscriminately into -I reams and lakes. All inorganic salts except nitrogen tend to remain in decomposing manure. If de- composing manure is subjected to leach- ing, readily available nutrients are re- moved from the manure in varying quan- tities. Figure 15 and table 11 present data on the quantities of nutrients that can be leached from manure. Potassium is most easily leached, whereas nitrogen and phos- phorus are more resistant to leaching. Peperzak et al. (1959) found that both total and inorganic phosphorus concentra- tions of manure piles increase with time for about the first 10 years of stockpiling. Concentrations of total and inorganic phos- phorus measured in manure piles of 15 and 20 years of age were less than those of 10-year-old piles. Mineralized nitrogen resulting from ex- tensive decomposition (table 11) is more easily leached than is organic nitrogen (fig. 15). As water-soluble nitrogen in manure is the only form available to plants (Heck, 1931), losses of this form by leach- ing or volatilization from manure piles or from field-spread manure is particularly tragic. Heck (1931) found that 20 per cent of dung nitrogen is mineralized to the am- monium form in 30 days in fermentation piles. Fifty to sixty per cent of the nitrogen in manure in soils can be mineralized over a period of 1 year (McCalla et al, 1970) ; nitrogen in the liquid manure fraction is primarily in the form of urea which can be hydrolyzed to ammonia in 2 to 5 days under favorable conditions (Salter and Schollenberger, 1939). The majority of the nitrogen in poultry manure is in the 30 "O c o D. o c/i SO o - >> r q ^1 T3 C o D. ++ 3 oo o u-> (N ri u~ r-~ ON m >c &2 ir (N ri O >C NO oc ri r*", — r C) ri ri O — r o O m m -a H o d d d 3 d C d d d d c 3 o 0- T3 C 3 C Q m vO oo r» nC LTi r o r~ tj- rn ON ON oo ur r ON m o Tt ur oc O CO n cn) r\ c~ r q r<- rn 00 c 3 O CL d d d d C ~ d c d d v- >> r NO _ cn .it 'St oc 3 * _ _ _ _ _ _ O * r— t-- r- r~- r~- r~ r-~ C/J nO nO ON ON ON nC nC ON ON ON nC ON a C 3 "3 3 3 r- 3 3 3 On u a> o^ 73 73 73 O^ «« S t« ^c c/3 V) C/5 i 73 73 ) •• DO -; ^ ■ • a .— cu .— fr« S* '73 .— O • — o 'r- '3 Z '5 ^6 73 ir; '« > '3 V* "3 c « >> 5 H f- 1 ^ 5 h " H -73 H tu H H •i H -J h- H I OQ H c75 Q 00 I tyN - 2 & 5 S 31 100 80 *°"»^ 1 o * a ^ ^-"•o- " *"" — — — .o_ Nitrogen 60 a ^"**o^ Phosphorus o< ^"^„ ~~^ — Tr- c | 40 '"«v a^ Sulfur c Po assium ^ "****X* " 20 10 lis water oppln Fig. 15. Per cent nitrogen, phosphorus, sulfur, and potassium remaining in dairy feces after continued leaching with water (from Azevedo and Stout, unpublished data). form of uric acid, which uricolytic bac- teria rapidly oxidize to ammonia. Bur- nett and Dondero (1969) found that 89 per cent of the uric acid in fresh poultry manure disappeared after 7 days; over 97 per cent was gone after 21 days. Uricolytic bacteria were also active in anaerobic ma- nure slurries, and less than 1 per cent of the original uric acid remained after 7 days. Because ammonium-nitrogen exists in equilibrium with gaseous ammonia which can be volatilized and lost to the atmos- phere, temperatures, alkalinity, and dry- ing are important factors in determining quantities that might be lost. Table 12 shows losses of total- and ammonia-nitro- gen from manure exposed to field drying conditions. Heck (1931) hypothesized that the initial rapid loss of one-half of the ammonia-nitrogen was from ammonium carbonate salts, whereas the remaining half was released more slowly from the salts of volatile acids. The warmth of aerobic composts would encourage the vol- atilization of ammonia. Ammonia can be lost from alkaline aqueous manure treatment facilities (Ed- wards and Robinson, 1969; Stratton, 1969; Chang et al, 1971) . Ernst and Mas- sey (1960) showed that up to 50 per cent of the applied urea nitrogen could also be lost from soils at pH 7.5. Greater losses would be expected in soils with higher pH's. During decomposition of manures, am- monium-nitrogen can be oxidized to nitrite and then to nitrate under conditions fav- oring aerobic bacterial activity. Unlike ammonium, nitrates carry a negative charge, are not held by the cation-ex- change complex, and are more easily leached from manure piles as well as from manured soils. Under conditions favoring proliferation of anaerobic bacteria, how- ever, ammonium is not oxidized to nitrate, and virtually all nitrate present can be denitrified to nitrogen or nitrous oxide gases and lost to the atmosphere. Losses of nitrogen from nitrates that move from aerobic to anaerobic zones in manure piles, soils, or water can be quite high. Nitrates are reduced to nitrite and am- monia by certain bacteria. Unlike the proc- ess of denitrification, both aerobic and anaerobic bacteria can effect this reduc- tion. This reaction would result only in a change of form of nitrogen present in the manure and not in a net loss. Most of the nitrogen in aerobic composts is in the un- available organic form, but most of the nitrogen in anaerobically-fermented ma- nure is in the form of ammonium. Figures 16 and 17 depict the common fate of nitro- Table 1 1 EFFECT OF FERMENTATION AND LEACHING ON r HRTILIZiR VALUE OF CHICKEN MANURE* Manure source 1 listory Approximate co nip >sition N | P K /XT cent Droppings Prompt drying 4.2 2.8 2.5 ( enter of moisl stockpile . Fei mentation and loss of N as ammonia 2.1 2.S 2.5 < hitsulc of stockpile . . . Leaching b\ rain and fermentation loss 1.8 2.7 1.6 l imiii Martin el al 32 Table 12 LOSSES OF TOTAL-NITROGEN AND AMMONIA-NITROGEN FROM FERMENTED MANURE EXPOSED TO DRYING IN STILL AND IN WINDY AIR* No wind 82 m.p.h. v\ind Time and temperature of exposure Loss of total- nitrogen Loss of ammonia- nitrogen Loss of total- nitrogen Loss of ammonia- nitrogen 12 hours: 20 C 36 hours: 20 C 3| days: 20 C 7 days: 20 C 7 8 dayst; HO C . . . . mg 9.0 27.2 37.8 42.2 56.2 per cent 1.1 23.4 32.4 36.2 48.2 per cent 15.2 46.0 63.9 71.3 95.0 mg ->9 "> 36.1 41.5 43.5 56.4 per cent 25.1 30.9 35.6 37.3 48.3 per cent 49.4 61.0 70.0 73.5 95.2 "From Heck (1931). Original samples weighed 20 g. f After air-drying in the open for 7 days, the residue was placed in the oven at 80°C for 24 hours. gen from manure stored in aerobic and anaerobic piles, respectively. In compact anaerobic piles organic nitrogen com- pounds are slowly converted to ammonia, and virtually no ammonia is lost from piles that are kept wet. Under aerobic dry- ing conditions, ammonia formed from the decomposition of organic matter is oxi- dized to nitrate. Some ammonia is used in the synthesis of microbial protein; a substantial portion of the ammonia is volatilized. Some nitrate could be deni- trified in the commonly anaerobic cen- ter of the pile. Management of decomposition processes The purpose for which manure is to be used should determine management of its decomposition. Wastes can be handled as solids, liquids, or a combination of both. Nitrogen and organic matter in wastes can Nitrogen as Ami de Other N Compounds Start AEROBI C DECOMPOSITION NH : . 1 1 NO 3 1 1 Am 1 de 8 Other 42 NH 3 N0 3 Ami de Other Stored at Stored at temperature 26 C ^15 C Fig. 16. Changes in nitrogen compounds (per cent of original total N) in farmyard manure dur- ing aerobic decomposition for 56 days (from Russell and Richards, 1917). trogen as ANAEROBIC )E COMPOS I T 1 or Other N Compounds NH-, 29 Ami de 9 Other 57 At Start Stored at 6 C Stored at 26 C Fig. 17. Changes in nitrogen compounds (per cent of original total N) in farmyard manure during anaerobic decomposition for 50 days (from Russell and Richards, 1917). 33 he either conserved or rejected, and nui- sances can he either minimized or ignored. Proper control of decomposition can effect any of these results. Until about 20 years ago. good manure management was directed toward minimiz- ing loss of nutrients and organic matter from decomposition and weathering. With the recent proliferation of concentrated sources of manure production, however, the chief concern is to minimize nuisance aspects of manure during storage and to encourage loss of hulk — conservation of manure for land application has become of secondary importance. Numerous manure-handling systems have been developed to advantageously utilize natural decomposition processes. I nlike the original waste, animal manure stabilized by decomposition is a semi-inert and odorless substance which can be used or sold without offending neighbors or cus- tomers. The bioactivity of stabilized ma- nure remains at a low ebb. Solid manure can be composted, but liquid-handling sys- tems are favored when large quantities of water are already in use on the farm and sufficient land is available for subsequent irrigation with the effluent. On-site composting. Manure begins to decompose at the site of deposition (e.g., on corral surfaces or under cages). Al- though variations in climate and animal density will determine the amount of de- composition, moisture can be managed to increase or decrease the rate of stabiliza- tion (Grubetal., 1969a, b) . Howes (1968) found that composting of poultry manure directly underneath cages could reduce the bulk by one-half and could also minimize odor and fly nuisance problems. A 50 per rent reduction of organic matter in cattle wastes can be attained in some feedlots (McCallaand Elliott, 1971 ). The fate of manurial nitrogen can also be influenced by manure management. In the laboratory. Stewart (1970) simulated urine additions to a feedlot surface. One surface was kepi wet (equivalent to a stock- ing densit) of one steer per 7 square meters) and the other surface was allowed to dry before more urine was added. Twenty-five per cent of the nitrogen added to the wet surface was lost as ammonia to the atmosphere, and nitrate leached through the profile as nitrate and ammonia accumulated. Ninety per cent of the nitro- gen added to the dry surface was lost as ammonia. Ammonia and other volatile ni- trogen compounds can be detected in acid traps and waters surrounding feedlots ( Hutchinson and Viets, 1969; Elliott et al., 1971). Anaerobic manure packs below older feedlots will encourage nitrate losses through denitrification. Mielke et al. (1970) found minimal nitrate concentra- tions below an old feedlot surface. The redox potential in the manure pack was sufficiently low to allow denitrification. High concentrations of carbon dioxide and methane gases in the soil atmosphere be- neath another feedlot were noted by Elliott and McCalla (1972). Denitrification was certain to be occurring since the redox value was low enough to allow methane production. Disturbance of the anaerobic pack by scraping or cleaning corrals down to the soil surface would encourage nitrifi- cation and leaching of nitrates. Stockpiling and composting. Copra- phagous insects play important roles in helping dispose of pasture and rangeland manures by degrading much of their or- ganic contents (Anderson, 1966a). The common housefly has been found to effec- tively convert fresh poultry manure to a semi-dry, crumbly waste material within a week under controlled conditions (Cal- vert et al., 1970). The role of insects in the degradation of manure should not be overlooked. Composting methods for animal ma- nures range from occasional stacking to elaborately controlled systems with forced aeration (Livshutz, 1964; Senn, 1971) and gradations in between these two. All methods eventually seem to result in suc- cess although each varies in the amount of nitrogen lost, odor produced, and the time needed for complete stabilization of waste. Nitrogen and organic matter losses from compact anaerobic fermentation piles are generally less than 10 per cent (Heck, 1931). Because organic nitrogen is min- eralized to ammonia and is offered to crops in this readily available form, anaerobic storage of manure was recommended to farmers by experiment stations up until about 30 years ago. Unfortunately, wet anaerobic piles are generally odorous and society now seems less tolerant of odors and other nuisances than were previous generations. Aerobic composting thus re- flects changing attitudes towards fertiliz- ing value and nuisance control. Aerobic 34 | FRESH MANURE W^/A R TT ^ MAN UR E 2000 lb Weight of fresh manure W'&WffiM B3« loss 485 lb organic matter in fresh manure mw/////////////A ■»>... 12.3 lb N myw//MW///Mm m ^ 1 65 lb Aval lable N vx&m *« '•«« 2 7 lb P EliilSli No change 16 lb Avai lable P M*WMMWM//M/MW/, 12.8 lb K ^MWW////////////MWMm. No change 16:1 C:N Ratio W/MW///A «4.iKr.„. Fig. 18. Effects of rotting mixed horse and cow manure under shelter for 3 months (from Salter and Schollenberger, 1939). composting processes are generally odor- less, but losses of organic matter and available nitrogen reduce the absolute value of the original manure (fig. 18). Relative nitrogen concentrations in fin- ished composts are generally higher than in the original manure because organic matter and total weight are reduced faster than the nitrogen (Turk and Weidemann, 1945) . The nitrogen is mostly in the form of proteinaceous microbial cells, which must be mineralized before nitrogen is available for crops. The decrease in the carbon : nitrogen ratio of manures during composting is often enough to prevent immobilization of soil nitrogen in micro- bial protoplasm which occasionally occurs when some manures containing straw are applied to soil. In such cases, nitrogen in composts would be more available to crops than nitrogen in the original organic material. Ease of handling or marketing otherwise unacceptable manures can be sufficient reason for composting or drying manures. Stabilized composts can also be re-used as animal bedding (Howes. 1966; Senn, 1971). Aqueous treatment systems. Aqueous treatment systems are classified as either aerobic or anaerobic but are generally exclusively neither. Predominantly anaer- obic systems are typified by the lagoons common to midwest swine farms. 6 The success of anaerobic lagoons, as measured by reduction of volatile solids and BOD with the minimum of odor, varies with climate and loading rate but is generally marginal at best. Freezing climes restrict biological activity, and overloaded lagoons are disastrous. Animal waste holding ponds are operated differently in the warmer California climates, and have been quite successful in reducing storage and handling problems (Meyer and Baier, 1971). Waste reduction is not a primary requisite, as liquid is emptied periodically from these ponds for crop irrigation. The aerobic surface and the moderate load- ings minimize odors from anaerobic di- gestion occurring below the surface. Nitrogen losses from the nitrification- denitrification processes and ammonia volatilization are considerable, although nitrogen conservation is a secondary con- cern. Recent evidence that manure lagoons and holding ponds form a bottom seal that restricts water infiltration ( Koelliker and Miner, 1970; Meyer and Baier, 1971) in addition to the actively denitrifying layer at the pond bottom, seem to assure that nitrate leaching from these ponds is min- imal. Artificially aerated aqueous systems have been developed for nuisance-free storage of animal manures. The oxidation ditch (Loehr et al., 1971) is an effective method of introducing oxygen into the liquid ma- nure, and many animal producers use this system, especially in the midwest and Canada. Losses of manure nitrogen as ammonia and nitrogen and nitrous oxide gases from oxidation ditches range from 15 to 50 per cent of that added (Edwards and Robinson. 1969; Loehr et cd., 1971). 5 The term "lagoon" implies a sewage disposal system in which organic matter is retained semi- permanently for microbial degradation to a lower energy level. A "holding pond" is intended primarily as a management aid for convenient holding prior to spreading of waste water, although substantial amounts of microbial decomposition and stabilization of organic wastes may occur in holding ponds. 35 Chang et al. (1971) suggest that aerobic systems could be managed to induce even greater losses of nitrogen if desired. Stabilization of manure in liquid sys- tems depends a great deal on loading rate, climate, and aeration, and the process is generally slower and more sensitive than with solid systems. In aerobic systems, volatile solids in dairy wastes can be re- duced 36 to 51 per cent in 6 months of ideal conditions (Dale and Day, 1967). Greater reductions are associated with low loading rates. There is a greater reduc- tion at higher temperatures (Nye et al., 1971). Cattle wastes lost about one-half of their total solids when decomposed in a heated anaerobic digester (Loehr and Agnew, 1967). Fibrous particles that com- prise the bulk of cattle manure can be separated out to speed digestion of the liquid. Effect of bedding, feed additives, and manure amendments Straw or other bedding material retains the liquid portion of animal manures and prevents loss of ammonia during drying — two-thirds of poultry-manure nitrogen can be lost as ammonia if litter is not used, but only one-third is lost if droppings fall on litter ( Eno, 1966) . Acid-forming chem- icals, such as phosphate or sulfate, can also be added to droppings to reduce ammonia volatilization, but nitrogen saved does not warrant the cost of these chemicals unless their fertilizer value can be recovered by field-spreading of manure. Lime can pre- vent the breakdown of uric acid in poultry manure, but it will induce ammonia losses in older manure where uric acid has already been converted to ammonia. Feed and feed additives can affect the decomposition rate of resultant manures. The rate of oxidation of cattle manure, as measured by the BOD test, was higher for manure from grain-fed cattle than for that from cattle fed a grain-silage mixture (Mills, et al., 1969). The BOD of manure from pastured cattle was shown to be lowest of the three. Algicides or bacteriostats added in feed or to manure during storage may affect decomposition processes (Morris, 1966). About 75 per cent of the chlortetracycline fed to feedlot cattle in one study was excreted and gave a concentration in fresh manure of 14 milligrams per gram (El- mund et al., 1971) . Evidently, the excreted antibiotic selects for bacteria which are inefficient in the decomposition of manure, and probably modifies the nature of an- imal digestion processes to' give a manure more resistant to decomposition. BOD tests showed that 38 per cent more organic matter was oxidized from the untreated- steer manure than that from steers fed chlortetracycline. In addition, cross-seed- ing experiments showed that microflora from treated manure oxidized 40 per cent more organic matter when transferred from antibiotic-rich manure to manure from untreated steers. Microflora from untreated-steer manure oxidized 31 per cent more organic matter in treated-steer manure than did the indigenous micro- flora. Copper oxide and antibiotics fed to hogs altered the microbial population and BOD of the swine lagoons (Clark, 1964), and copper fed to swine changed the BOD of their manure (Ariail et al., 1971). The modified decomposition processes which take place in manure containing antibiotics and other such feed additives may result in a more odorous decomposition (Mess- mer and Berry, 1964; Morrison et al., 1969). NUISANCE FACTORS OF MANURE One of the more noticeable results of changing public attitudes toward manures i- ,in inevitable byproduct of food produc- tion has been the growing intolerance of their nuisance aspects. (In the I . S., animal manure odors are not regarded as the "breath of spring"' as is still the case ifi some picturesque European rural areas.) Nuisance byproducts of animal manure production include esthetics of appearances, flics, odors, dust, and feath- ers. Determinations of what constitutes acceptable or unacceptable nuisance levels to surrounding communities may become so involved with emotional and political connotations that compromises are often unattainable except by court decisions. Esthetics and public relations In California, as in other state's, attitudes toward esthetics of the animal industry have been aggravated by modern trends 36 toward economically-desirable, high-den- sity animal-feeding operations and by en- croachments of suburban populations into formerly rural areas. Where 100 cows might have gone either unnoticed or re- garded as an esthetic attraction in a rural community, a changeover to 200 in the same location may generate neighborhood tensions or hostility. If the neighborhood becomes decidedly suburban, nuisance and esthetic complaints are generally com- pounded. Frink (1970) commented: "Our urban population has largely forgotten and has no desire to be reminded of farm sights and smells." And, writing about emotion-charged issues relating to some of the animal production units in Southern California, Ottoboni (1971) remarked: "The esthetic standards of the American suburban public are not compatible with the insults to the senses as are created by thousands of incontinent animals in neigh- boring unsightly pens." Negative attitudes on the part of the animal manager or the surrounding pub- lic rarely lead to logical compromises of their common problems. Positive responses from public relations can be forthcoming, however, when the industry clearly shows that it is concerned with solving problems of manure management and disposal, im- proving esthetic appearances of animal quarters, and demonstrating permanent beneficial contributions of the industry to the welfare of the community. These latter approaches may be more productive than equivalent efforts spent in parrying com- plaints by adversary methods. Dairies have apparently had fewer prob- lems with esthetic issues than have other animal industries — small dairies have long been traditional parts of commu- nity scenes. Family-operated dairies have earned social and visual acceptance as community assets, and have also added a pleasing pastoral charm by providing us scenes of small herds of cattle grazing on lush pastures. More recently, favorable public relations have been fostered by images of clean milking parlors, sanita- tion and safety of milk products backed up by routine inspections, and signs such as "Grade A" milk and "Dairy Award" placed conspicuously alongside roads that pass by dairies. However, some designers of modern dry lot dairies have neglected these pleasing esthetic traditions, and have also failed to provide for alternatives that might aid in ameliorating public reactions against dairies as neighbors. Poultry production operations have usu- ally been screened or segregated from heavily populated areas. The small space allotment per bird has made separation of modern poultry enterprises easier. Noise and odors of all but the smallest of these operations made such separation desirable as the shift-over from small-scale to large- scale poultry production took place. Beef cattle feedlots face more disad- vantages in making esthetic improve- ments than do most other livestock oper- ations. This is because the large number of animals (even in moderately-sized feed- lots) require quite a few acres of land. Feedlots, with their storage bins and machinery required for large-scale cattle feeding, have generally resembled an in- dustrial rather than a pastoral activity, and this affects community tolerance of them. As one of six coordinated solutions to clashes between community sensitivities and feedlot operations, Ottoboni (1971) suggested an "industry esthetics improve- ment program," including ". . . the use of trees and greenery to change the indus- try's image from that of a 'feedlot' to one of an 'agricultural park.' " This commonly neglected suggestion for park-like appear- ances could apply as well to any other livestock and poultry operation. There are also other advantages provided by trees and greenery: they can be natural deodor- izers (or odor maskants in the case of some plant species) and shrubbery may be used as fly breaks, dust and feather breaks, weather modifiers, sound absorb- ers, and runoff absorbers. Obviously, shielding animal production operations from the public eye with trees or other devices (e.g., building design, microtopographic considerations in loca- tion, etc.) are practical means by which community impressions of livestock pro- duction operations can be improved. Im- pressions of the feedlot as a treeless, wind- swept, uninviting, uninteresting scene can be changed through architectural land- scape and building arrangements so as to reduce nuisance impacts of unavoidable levels of fly, dust, and odor byproducts generated by confined livestock. In the long run. however, minimizing neighbor- hood complaints about esthetics and nui- sances will result only from physical sep- aration of animal operations from highly 37 populated areas. Governmental-commu- nity-industry programs directed toward protective zoning for bonafide agricultural operations and the development of local land-use plans appear to he desirable trends for the future. Some states have already responded with imaginative but practical programs of this sort (e.g., New York's "Agricultural District"). Califor- nia lags considerably behind in this re- spect. Health aspects of manure nuisances Flies, odors, and dust are the more com- mon nuisances confronting livestock oper- ations in California. Flies and dust have significance for animal and human health and for general animal performance, and the generation of toxic gases has to be considered when designing manure dis- posal systems intended for closed animal quarters. Dust has been suspected of lowering resistance of poultry to certain diseases (Anderson et al., 1966), reducing weight gains and impairing general health in cattle (Wadleigh, 1968), and aggravat- ing allergic respiratory human ailments in children and the aged (Ottoboni, 1971). Bacterial spores carried by dusts, includ- ing dusts from ordinary soils, can be one vector of disease in animals and humans. Although experimental evidence is sparse, flies that contact both feces and food of animals and humans are com- monly thought to serve as vectors for cer- tain diseases. The housefly is said by some to be the most dangerous insect known, as it can serve as a vector for about 30 human diseases I West, 1951). Gwatkin and Mitchell (1944) were able to demon- strate tlie transfer of Salmonella pullorum from inoculated poultry feces to poultry food by flies allowed access to both- many chickens developed salmonellosis and died. Biting flies (e.g., the stable fly) can irri- tate cattle and decrease weight gains (Cheng, L958), as well as transmit some diseases mechanically l»\ biting. In at least one reported instance I Freehori) et al., 1 92.") ) . the sheer nuisance of the house- (l\ reduced milk production by dairy cows. Dangers of manurial gases in con- fined quarters. Some odorous gases such as hydrogen sulfide and ammonia pro- duced b\ microbial activities in manure may become dangerous to humans and animals if allowed to accumulate in suffi- ciently high concentrations. Because both ammonia and hydrogen sulfide can form supersaturated solutions with water, stir- ring of liquid manure can rapidly release these gases in quantity. Hydrogen sulfide is the more toxic of the two, and a short period of exposure to sufficiently high concentrations of this gas may be lethal. Ammonia is distressingly unpleasant long before lethal concentrations are reached. Confinement situations normally do not generate lethal concentrations of these gases, but ventilation breakdowns and in- adequate ventilation during manure-pit stirring and cleaning have resulted in human and animal deaths from direct toxicity and from asphyxiation (Taigan- ides and White, 1969; Muehling, 1970). Prolonged exposure to relatively low levels of ammonia, such as those found in some poultry and swine houses, has been found to decrease feed conversion efficiency in swine (Stombaugh et al., 1969) and maturation (Charles and Payne, 1966) and resistance to certain diseases (Anderson et al., 1964) in chickens. Manure-produced methane gas seldom reaches explosive concentrations (5 per cent of air volume) in animal-confinement facilities, but there have been explosions in liquid-manure pits. The reader is referred to the excellent review of manurial gases by Taiganides and White (1969) for more detailed in- formation. Flies With the advent of large, commercial, confined feeding facilities for animal production, populations of cosmopolitan "'filtli-fl i<*^,"" have increased dramatically (Anderson. 1966a, b) . In an excellent summary on the entomological aspects of manure. Anderson (1966a) states that more than 50 species of flies, including the more obnoxious cosmopolitan (lies, can be attracted to and breed in the accumu- lated mass of manure under confined poultry, although only one or two insig- nificant species are attracted to range poultry droppings. Confined layer hens in wire (ages cannot practice their own form of biological control (consumption of the fly larvae). Conversely, manure in Cal- 38 Tami i I 3 DOMESTIC FLIES COMMONLY ASSOCIATED WITH MANURES OF CONFINED ANIMALS IN CALIFORNIA* Number days for life cycle (egg to adult )t I ype of manure Type of fly cow steer hog horse poultry Black blow fly. Phormia regina Blue blow fly, Calliphorinae species .... Green blow fly. Phacnicia species Black garbage fly. Ophvra species Coastal fly, Famiia femoralis Flesh fly, Sarcophagidae species House fly, Musca domestica Little house fly. Fannia canicularis Stable fly. Sionioxys ca lei irons False stable fly. Muscina species Drone flv, Tubifera tcnax 10 15 8 10 14 8 8 24 21 14 21 X X X X X X X X X record X X X X X X // fix in X X X X X X X X X nanurei X X X \ \ \ \ X X \ \ X \ X *From Loomis el at. (1967). tRelative time during warm summer temperatures. Cooler or very hot temperatures will, respectively, retard or accel- erate this developmental period. +The symbol x denotes a recorded occurrence of that species of fly in that type of manure: the symbol — indicates that species of fly is not commonly associated with that particular type of manure. ifornia fecdlots attracts at most seven spe- cies of flies, but most of these are obnox- ious pests to cattle and man. Individual cowpats in pastures may contain more than 40 species of flies although only two (horn fly, Haematobia irritans, and face fly, Musca autumnalis) can be considered serious pests. The vast accumulation of manure in pens is too great to be disposed of by the multitude of coprophagous flies that are so efficient in disposing of drop- pings in pastures. Table 13 summarizes the species of troublesome flies common to California's confined-animal manures. Each species has habitat preferences and will build up in great numbers only when their habitat requirements are best met. In one survey of fly production in the lower San Joa- quin Valley, rattailed maggots were found in wet manure (e.g., around defective troughs) and false stable flies {Muscina spp.) were found only in the early spring (Walsh, 1964). The housefly {Musca domestica) and the stable fly (Stomoxys calci trans) were generally the most abun- dant, however. The housefly was also found to be the most abundant species in Imperial Valley fecdlots (Soroker and Poll. 1968). Walsh (1964) found the moist manure around the water trough to contain fly larvae in 58 to 69 per cent of the samples collected. Samples from corral surfaces wet by accumulations of spring rain contained fly larvae 44 per cent of the time. In one survey of Im- perial County feedlots. manure on or around the water trough contained larvae 74 per cent of the time ( Soroker and Poll. 1964). I ntrampled areas, such as fence lines, were another major source of flies as were individual droppings in un- crowded corrals. Since the breeding and development of flies arc highly dependent on moisture content (fig. 19). management and design recommendations for reducing the num- ber of flies in feedlots usually emphasize moisture management and special atten- tion to design and cleaning of untrampled areas. Cable-and-metal-pole. rather than board-and-wooden-post corral construc- tion, aids fly-control programs for fecd- lots and dairies. Biological control mea- sures designed and administered by rep- utable companies have been successful in 39 PER CENT MOISTURE DEAL ( 1970) a Major i ty of 7 ann i a femes I i s developed Optimum for development of I arvae Fanma sp ±83 ~Y 82 I 64 60 Satisfactory for oviposi tion of Fannia canicular i 43 No development ~J~ 35 Of Fannia sp po 'a camcula 90 80 70 60 1 s T s J 50 40 30 20 10 KL I EWER and B0REHAM (1964) 83 -T- Moi sture I imi 1 for housef I y oviposi ti on SMITH e_t aj_ ( I960) _ If 85 33 J 30 Too dry for 1 oviposi tion of * No fly growth UCD DEAN'S TASK FORCE ( 1 9 7 ^ LOOMIS ( 1972) personal communication T 90 Development of Tub i fera tenax 1 Mo i sture I imi ts for housefly growth 53 -L Fig. 19. A rough guide to moisture conditions of manure required for breeding and development of some common flies. These data apply to fresh and partially decayed manure only, as there is some evidence that flies do not oviposit in composted manure even at moisture conditions that would attract oviposition on fresh manure (Eastwood et al., 1967; Senn, 1971). Chart was expanded from an original by Smith et al. (1960). supplementing fly-control measures of good feedlot management. Residual insec- ticides are less effective on mobile fly populations in open feedlots. Larvicides are recommended by the U. C. Experi- ment Station only in "emergency" situa- tions. Widespread uses of larvicides for fly control in the recent past have resulted in the development of larvicide-resistant flics (Georghiou and Bowen, 1966), with the degree of resistance being roughly proportional to the amount of insecticide used (Georghiou et al., 1972). Evidence also suggests that flics having developed resistance to one larvicide will mutate more readily when exposed to a second larvicide than will their non-resistant fore- bearers (Georghiou et al., 1965). Insecti- cides (larvicides) applied directly to ma- nure are detrimental to beneficial arthro- pod-. Where the onl\ manure management techniques to discourage flics were to appl) insecticides, the flies in some north- ern California poultr) ranches were not controllable (Burton et al.< 1965). Good manure management as part of the fly- control program did not cost more, and satisfactory control was achieved without insecticides. Insecticides are currently rec- ommended only in conjunction with inte- grated control and management measures (Anderson et al., 1973). Anderson and Poorbaugh (1964a,&) studied the ecology of various flies on poultry ranches in northern California and suggested possibilities for biological (integrated) control of certain pestiferous fly species. The black garbage fly (Ophyra leucostema) was found to prey on larvae of the common housefly, the little housefly (Fannia canicularis) , and others, killing from two to twenty of these fly larvae per day. Despite its ominous name, the black garbage fly does not congregate in houses and is not considered a nuisance. Con- veniently, the black garbage 1 fly tends to congregate at night in shrubs and trees outside of poultry houses, whereas the housefly and little housefly rest inside poultry houses. Residua] sprays or tapes Or cords impregnated with insecticide and 40 Major i t y of fly predators attack these stages Fig. 20. The stages of the life cycle of the common housefly (Musca domestica) which are attacked by various predators and parasites. hung inside these houses can reduce nui- sance-fly populations while sparing their predators, the garbage flies, for further housefly control. Axtell (1970) found that the presence of black garbage flies pre- cluded build-ups of a nuisance population of houseflies and little houseflies on some North Carolina poultry houses; selective spraying and baits were also effective. Less frequent manure removal schedules also favor the predator population (Peck and Anderson, 1970), whereas frequent removal interrupts development of an ef- fective predator population. Legner and Brydon (1966) recommended removal of manure from alternate sections of the poul- try house in order to maintain the pred- ator and parasite populations. Also, move- ment of manure liberates ammonia, an attractant to gravid domestic flies. Other predators of flies include certain species of beetles, bugs, mites, earwigs, and ants as well as some vertebrates. Parasites offer another effective means for biological control of flies which hatch in manures. Parasites, such as some species of hymenopterous (wasp-like) insects, at- tack the fly at the pupal stage of the fly's life cycle and thus exert a greater influ- ence on subduing fly populations than do other parasites and predators which gen- erally attack at the egg or larval stages. Only about 1 per cent of fly eggs develop to the pupal stage (Legner and Brydon, 1966) and wasp-like parasites attack and lay their eggs in the tough pupae. Gen- erally, they will choose the healthiest pupae and leave the weak ones to pass on their poorer genes (Legner and Otton. 1968) . Figure 20 shows the various stages in the life cycle of flies and the sites of attack by predators and parasites. In experiments at one poultry ranch near the coast in southern California, Leg- ner et al. (1966) found that introduced wasps increased parasitism of the predom- inant coastal housefly (Fannia jemoralis) . Houseflies and little houseflies (F . canic- idaris) were also attacked although the housefly pupated more deeply in the ma- nure of dirt floors and often escaped para- sitism. Hymenopterous parasitism of de- sirable predator flies, such as the black garbage fly, was well below 50 per cent. An effective but often neglected design- management fly-control practice is to screen or otherwise enclose the poultry house (Bramhall et aL, 1966), but screens should be vacuumed frequently to retain ventilation effectiveness. The cost require- ments of increased house maintenance sometimes intimidates poultry owners. Screening-in of poultry-house fly popula- tions keeps them from bothering neigh- 41 bors, and facilitates integrated fly control by reducing the numbers of attracted flies which would otherwise breed in the fresh manure. Screened enclosures are consid- ered to be impractical for modern feed- lots, as areas which must be enclosed are generally much greater than for poultry. Trapping procedures, though not pop- ular with entomologists, may supplement integrated control in enclosed confinement areas, and experimentation with fly traps in both open and confined situations should be encouraged. A completely different approach to feces-fly relationships has been taken by other experimenters (Miller and Shaw, 1969; Calvert et aL, 1971) who examined some results of fly growth in poultry manure. Larvae of houseflies grown on fresh poultry manure reduced fecal or- ganic matter by 80 per cent and moisture was reduced by one-third. The resultant residues were crumbly, essentially odor- less, had a moisture content of 46 to 50 per cent, and the dried, ground pupae formed a balanced diet for chicks. The radical change in the philosophy of de- sign and management of poultry houses necessary to utilize this new concept re- quires adaptations that may delay conver- sions by poultrymen until the economic advantages are clearly demonstrated. Odors Of all the nuisances related to manures, odor is perhaps the most readily notice- able but least definable and most difficult to control. Although odorous manurial emanations can be characterized chem- ically, odor characterizations as nuisances are often subjective. The odor of freshly voided or dried livestock manure is inoffensive to most people, but odors produced by anaerobic bacterial activity during fermentation of wet manure can be astoundingly offensive to the uninitiated. Using chromatographic techniques, White et al. 1 1971 ) tentatively identified hydrogen sulfide, methanethiol, dimethyl sulfide, diethyl sulfide, propyl acetate, n-butyl acetate, t rimethylamine, and ethylamine as fermentative decompo- sition product^ from dairy manure. Di- methyl sulfide was found to be the prin- cipal sensor) odor in anaerobic dairy wastes. |,ut aeration reduced or eliminated the odorous sulfide compounds. Amines were found to be the major odorous com- pounds around cattle feedlots (Stephens, 1971). Different feeds are thought to in- fluence odors of cattle manure. Cattle feeders in California generally believe that milo in the cattle ration results in a more odorous manure than that produced by cattle fed with other grains. Although amines, amides, alcohols, sulfides, car- bonyls, and organic acids were detected in a confined swine building atmosphere by means of gas chromatographic tech- niques, the major constituents of the odor were of the amine and sulfide groups (Merkel et al, 1969). Deibel (1967) identified butyric acid, ethanol, and acetoin as the chief volatile compounds in accumulated poultry ma- nure. Freshly excreted manure was essen- tially devoid of these compounds, as was a comparable sample of accumulated ma- nure previously treated with a bactericide. There is also a direct relationship between odor and fatty acids in stored liquid poul- try manures (Bell, 1970). Reduction of fatty acids and consequent control of odors was accomplished by aerating sufficiently to oxidize 37 per cent of the BOD of the liquid waste (Bell, R. G., 1971). Other systems of short-term minimal surface- layer aeration have been applied to reduce odors of stored liquid dairy waste (Barth and Polkowski, 1971 ; Ogilvie and Dale, 1971). Higher moisture levels create greater percentages of anaerobiosis in manure, and odors from amines and sulfides pro- duced by anaerobic biological conversions of manure can be quite offensive. Luding- ton and Sobel (1970) found a direct re- lationship between offensiveness of odors and moisture conditions in poultry ma- nure. Where water had been added to the manure, the odors originated pri- marily from hydrogen sulfide and were distinctly offensive. A study of southern California and Arizona feedlots I Anon.. no date) revealed a general consensus among area cattle feeders that odors in their feedlots reached problem dimensions when moisture in the lot surface exceeded .^. r > per cent. As is the case with Hies, it seems that odors can be controlled by reducing manure moisture to less than 35 per cent. Apparently, similar compounds are re- sponsible for odors of various animal manures. Various combinations and con- 42 centrations of these compounds must ac- count for the diverse but distinctive smells of manures from different animals and from manures in different stages of an- aerobic or aerobic decomposition. In feed- lots, a surface layer of aerobic manure is usually sufficient to control obnoxious odors, but frequent manure removal does not solve the odor problem completely. As problems with odors are prevalent when the manure is stored or held before final use or disposal, one of the main functions of a storage facility should be to temporarily stabilize the manure. For odors, stabilization could include drying, aeration, or treatment with various com- pounds. Storage facilities for animal ma- nures include compacted soil and concrete surfaces for piling or mounding, ponds, tanks, and closed buildings. The beneficial effects of aeration for odor control are most apparent in ponds, lagoons, and other liquid systems. Numerous mechanical de- vices and systems to aid aeration have been tested with some success, and many are available commercially. Shal- low ponds, with high surface-area-to-vol- ume ratios, effect oxygenation without me- chanical agitation of the liquid. Although quite effective, these ponds must occupy larger blocks of land area than are gen- erally practicable. In California, it is com- mon practice to construct deep (greater than 8 feet) manure holding ponds. At recommended loadings, odors are dilute and unnoticeable in most rural areas be- cause the surface layer remains aerobic even though the ponds may be distinctly anaerobic at lower depths. Surface mats that form in many ponds are often the major source of odor. Numerous chemical compounds reputed to eliminate odors in manures have been tested for effectiveness. Burnett and Don- dero (1968) evaluated 40 commercial compounds by using organoleptic (human olfactory sensing) tests. Masking agents consisting of aromatic oils used to cover the odor with a more powerful, but pleas- ant smell, and counteractants consisting of aromatic oils selected to reverse the odor were the most effective in controlling the odor of liquid poultry waste. Masking agents used over a long period of time are sometimes as annoying as the original odor. Some of the more effective commer- cial compounds last only a short while and their expense is often prohibitive. Lime and chlorine are sometimes effective, al- though amounts required arc expensive and their presence in manure could cause problems in its subsequent disposal. Para- formaldehyde is said to neutralize the ammonia odor from poultry manure i Selt- zer, et al., 1969). Potassium permangan- ate has been used with some success in controlling odors at one California feedlpt (Faith, 1964) . Hudson et al. (1973 ) found that potassium permanganate can be reacted with either ground hemlock, fir. or corncobs to form efficient industrial air filters for reducing concentrations of hy- drogen sulfide and mercaptans in air. Manganese dioxide formed on the saw- dust surface was thought to oxidize sulfide to sulfur. Similar reactions of potassium permanganate with carbonaceous mate- rials in feedlot manures could possibly account for reported odor reductions, be- cause odorous gases such as hydrogen sul- fide escaping from anaerobic sub-layers would have to diffuse through the man- ganese-dioxide-coated aerobic upper layer before escaping to the atmosphere. Odors can seldom be controlled to the satisfaction of close suburban neighbors — although obnoxious odors can be con- trolled to a considerable extent, some odor is always present and unavoidable wher- ever animals excrete manure. Even the most fastidious control or masking oper- ations are second best to location of the animal enterprise in an area where people are tolerant of the odor. Dust The degree of dust nuisances created by livestock confinement facilities is highly dependent on the amount of moisture in the manures. For example, at least 25 per cent moisture was necessary to prevent blowing manure dust in southwestern cat- tle feedlots < Anon., no date) . With poultry litter. 20 to 25 per cent moisture was suf- ficient to keep dust settled ( Claybaugh. 1965) . Koon et al. ( 1963 ) found that dust in broiler houses was decreased by higher absolute humidities. He found that the quantity of dust produced on litter was 50 per cent greater than from caged layers, and that amounts of dust were related to types of litter used. The dust from birds in wire cages consisted mostly of charged skin flakes and feather barbules. In another study. Anderson et al. I 1966 1 43 found that dust from broilers on litter reached a high of 1.16 milligrams per cubic foot (32.5 /xg per m 3 ) in the late morning and a low in the early morning of 0.025 milligrams per cubic foot (0.7 /xg per m 3 ) with an overall daily average of 0.39 milligrams per cubic foot (10.9 /xg per m 3 ) . A characteristic "chicken house" odor is carried in the dust (Bur- nett, 1969) . (Note that /xg per m 3 , or mic- rograms per cubic meter, is frequently used in technical literature to express at- mospheric burdens of particulate mat- ters). Moisture management will continue to be the most effective tool for controlling dust nuisances. A Tulare County study has confirmed that stocking rates can be manipulated to control dust in cattle feed- lots (Miller, 1962, 1963). Seventy-five square feet per head was optimum for that climate, while 50 square feet per head (5.5 sq. ft. per cwt.) was too wet (and odorous) and 100 square feet per head (8.5 sq. ft. per cwt.) was too dry. The denser stocking rates had the added advantage of reducing fly production due to frequent grinding of the manure by animal hooves, but such feedlot surfaces can virtually erupt with arthropod life after the cattle are removed (Soroker and Poll, 1964; Walsh, 1964). In the Imperial Valley area, most feeders have been reluc- tant to crowd the cattle to reduce dust be- cause of increasing the possibility of ani- mal heat stress. In one trial, allotments below 40 square feet per head reduced gains and 60 square feet per head was bet- ter during torrid weather (Morrison et al, 1970). Sprinkling the lots reduces dust normally raised by animals "playing" in the early evening (Palmer, 1967; Carroll et al, 1974), although total daily dust fall is not affected (Palmer, 1967). Dust reduction in the early evening is important because the winds start to blow in the southern deserts and nocturnal atmos- pheric inversion prevents vertical disper- sion of the dust (Carroll et al, 1974). Some feedlot operators have been cited by the California Highway Patrol for the traf- fic hazard created by dust blowing across highways. The gentle northwest breeze character- istic of summer afternoons in the San Joa- quin Valley can carry the lighter fractions of dry manure dust to adjacent fields (in 1956, a feedlol owner was sued by a vine- yardist for dust damage in a nearby grape field). In late afternoon the wind in this valley diminishes and dust concentrations can build up in a dry feedlot, causing cat- tle to cough. Sprinkling manures (with sprinklers or from tank wagons) palliates dust problems without increasing animal stress due to heat and humidity (Carroll et al, 1974), and fly and odor problems are not aggravated by the temporary sprinkling as long as excessive water is not added. When economic or other practical considerations preclude control by adjust- ing stocking densities, sprinkling may pro- vide an effective substitute. Moisture-nuisance relationships The three major nuisances of animal ma- ures, flies, odors and dust, are intimately related by their dependence on moisture conditions. Nuisance problems can be minimized if manure moisture is kept low enough to preclude serious odors and fly proliferation and yet sufficiently high to prevent dusty conditions. Successful man- agement of manure moisture requires skill and careful attention, but applications of moisture control techniques can be highly effective. Climatic influences upon moisture con- tents of manure can influence occurrences of fly, odor and dust problems. Generally, flies and odors are more of a problem in northern and coastal California zones of higher rainfall and fog, whereas dust is more troublesome in the less humid cli- mates south of Fresno (Loomis and Claw- son, 1970) . Area rainfall and water-use by the livestock operation can suggest varia- tions of handling moisture to minimize fly- odor-dust nuisances in combination. For example, operations in arid climates can take advantage of natural drying condi- tions to reduce moisture below odor-pro- ducing and fly-breeding levels, while add- ing moisture to control dust. Bressler and Bergman (1971) have suggested that auto- matic manure-stirring devices could hasten the drying of poultry manure; such devices could be most beneficial in months when climate makes drying of manure more dif- ficult. When manure is naturally liquid (e.g., duck manure) or kept wet and soggy by rain and fog, or where large quantities of water are being used (as with milking parlor wash-water in dairies), manure can he liquified for relatively nuisance-free 44 storage in holding tanks or ponds. Reduced labor costs and increased flexibility help offset costs of additional materials handling requirements if adequate farm acreage is available for proper use and disposal of the manure slurries. The rattail maggots of the drone fly {Tubijera tenax) thrive in manure holding tanks and ponds, but these are not normally considered nuisance flies, for they do not frequent homes or molest human food (Loomis et ah, 1967; Hart and Turner, 1965). In fact, drone fly lar- vae will consume some of the troublesome debris floating on manure holding ponds (Fairbank, 1963) . No houseflies will breed in liquid manure ponds (Hart and Turner, 1965). Mechanical separation of the solids from liquid manure renders both liquid and solid portions inhospitable mediums for fly development (Fairbank and Bramhall, 1968) . The solids are odorless, and the liquid can be used for sprinkler irrigation as it will not foul sprinkler lines. Gravita- tional separation of solids in large holding ponds (in which solids drop out as bottom sludge) is relatively cheap but less effec- tive. Where enough moisture has been added (above 85 per cent water) to make a slurry of the manure, it can be pumped and thin-spread to facilitate rapid drying and fly and odor reduction (Smith et al., 1960) . Thin-spreading techniques can be applied with some success to fresh or partially-dried manure, although achieving the required thin layer is more difficult. Where neither a liquid manure system nor quick-drying by natural or artificial means is practical, flies can still be con- trolled by storing manure in fly-tight bins or under plastic tarpaulins (Hart, 1957). The latter of these two methods is probably least expensive. Plastic Saran-type mesh tarps provide efficient fly control, while allowing natural drying through the weave (Smith et at., 1960; Eastwood et at., 1966) . When moisture in manure is re- tained by impermeable tarps, there is some odor produced by the anaerobic activity (Adolph, 1971) and some fly pro- duction when the tarp is removed ( East- wood et al., 1966). Adolph (1971) also recommends manure removal only during the season when fly breeding is minimal. Feather, mosquito, and field- spread-manure nuisances Two manure-related nuisances of lesser importance than dust, odor, or flies are feathers and mosquitoes. Loose feathers are a part of all poul- try operations. Normal feather-fall is easily incorporated into the manure be- cause feathers decompose with the rest of the litter, though more slowly. During a forced molt, however, feathers are shed from most of the birds in one house and can present a special disposal problem. Feathers float and form odorous mats on the surface of liquid manure ponds, and these fibrous particles clog drains and pumps; dry feathers can be blown to neighboring farms and create an unsightly nuisance. Mosquitoes are seldom a problem around manure ponds unless weedy growth is allowed to flourish along the edges of the pond (Fairbank, 1963). Irrigated pas- tures receiving waste daily for lack of a holding pond can be a prominent source of mosquitoes. In one recent study, Steel- man and Colmer (1970) found a direct relationship between organic matter con- tent of manure lagoons and mosquito pro- duction in these lagoons. Research data are needed to determine whether mosquito production in California manure holding ponds is significant in view of the pro- duction of mosquitoes in the thousands of acres of irrigated farmland surrounding these lagoons. The same types of manure-induced nui- sances arising from animal production in confined quarters can be present when manure is spread on cropland. I sually. though, the nuisance-period is seasonal and temporary and fields where manures are spread are sufficiently removed from dense populations so that relativelv few complaints arise. In addition, accelerated drying in the thin-spread manure layer (one-quarter inch or less) and intimate contact with the soil discourage flies and odors. Thicker layers of moist manure should be promptly disced or otherwise incorporated into the soil to help reduce their nuisance potential. 45 EFFECTS OF ANIMAL MANURES ON WATER QUALITY AND WATER-BODY ECOLOGY Water quality considerations Beginning with sea water as the earth's great natural supply of salt water, and with rain water as the sole continuing source of fresh water for streams and lakes, criteria for acceptable water quality generally range between the composition of these two extremes. Plant and animal wastes feature prominently in the ecology of all open-water bodies as sources of nutrients for the biota that inhabit streams, lakes, and seas. Nearly all fresh-water resources are viewed in terms of their multiple-use po- tentials. Thus, water quality guidelines are modified subjectively to suit diverse groups of water users, and a high-quality water for one kind of use may be low- quality for some other use. For example, phosphate compounds upgrade water qual- ity when added to water in a steam-gen- erating boiler in order to reduce corrosion and boiler-scale, but might be regarded as a polluting agent if returned to a stream, lake, or other water body (in contrast, the same phosphate would be considered bene- ficial if the phosphate-bearing water was to be applied to a phosphate-deficient soil) . Because of the great multiplicity of inter- ests among users of our water resources, water-quality standards have to be set in accord with the best judgement available in the light of prevailing circumstances. The presence of animal manures in sur- face waters is a normal part of the eco- logical scene; ingestion of fecal pellets and other organic materials is an important part of the natural feeding and digestive processes of many aquatic or semi-aquatic animals. Harmonious ecological adjust- ment in relation to water quality and ma- nures from large herbivorous animals is well demonstrated by Lake George in Africa. The lake has profuse growths of papyrus and floating-leaf water plants, and exceptionally high-yielding fisheries. Fecal discharges from herds of land-grazing hip- popotami fertilizes the lake directly. The lake water provides these animals with a comfortable daytime habitat including swimming facilities and some food. Tonr- IStfi consider tin 1 scene as idyllic and es- thetic, and residents appreciate the im portanl Supplies of lake fish. An ecological problem arises, however, when herds build up to a point where overgrazing near the lakeshore leads to soil erosion. Periodic re- ductions of the numbers of hippopotami are required in order to preserve ecolog- ical stability of the soil, water, and fishery resources of the lake. Nutrition of higher-order aquatic ani- mals is assisted by bacteria and fungi that attack organic debris whatever its source. When organic detritus is ingested, micro- organisms attached to it are stripped away and the undigested portion is passed on as fecal pellets to be continually cycled and reprocessed in the stripping, bacterial- production and ingestion sequence. Large fractions of organic debris in a coastal bay have been observed to be in the form of fecal pellets (Saunders, 1972) . Nutrients, odor, taste, color, and bac- terial overloads can easily result, however, from misplaced or misused manures or sewage discharged into water bodies. Or- ganic matter in manure also increases the BOD of water as part of the organic frac- tion and serves as an energy source for certain water-borne microorganisms — in- cluding yeasts, molds, bacteria, and proto- zoa — whose respiratory activities can de- plete waters of oxygen more rapidly than oxygen can be resupplied from the atmos- phere or from photosynthesizing aquatic plants. Waters depleted of dissolved oxy- gen promote the growth of anaerobic, fermentative organisms, but inhibit growth of aerobic organisms (e.g., fish). Manures in relation to fish kills. Although minor amounts of manure en- tering a large watercourse or reservoir would have little effect on dissolved oxygen in the water, great additions may quickly result in anoxia-caused fish kills. Agri- cultural wastes from "manure-silage drain- age"' were responsible for 4.8 per cent of the fish killed by pollutants in the U. S. in 1968, 6.2 per cent in 1969, 6 per cent in 1970, and 5.4 per cent in 1971 (table 14). In some geographical regions, such as the midwestern I . S., animal wastes have been responsible for a greater proportion of fish kills and a higher proportion of damage to fish. In Kansas. IS out of the 25 pollution-caused fish kills in 1964, resulted 46 Table 14 POLLUTION-INDUCED FISH KILLS IN THE U.S. AND NUMBER RELATED TO MANURES 1963 1971*. Fish-kill data b\ year Item 1963 1964 1 965 1966 1 967 1968 1 969 1970 1971 Total kills in U.S Per cent of reported fish kills traced to manures . . Per cent of total fish loss traced to manures .... 436 4.8 2.3 4X5 6.0 6.5 537 5.5 5.4 436 8.0 11.9 375 12.0 11.4 438 4.8 0.2 465 6.2 0.6 634 6.0 1.8 860 5.4 0.0 'Data from Federal Water Pollution Control Agency leaflets ••Pollution-caused fish kills" (1963 1971). from agricultural waste drainage (Loehr and Agnew, 1967) . Of the six fish kills in Kansas in 1965, five were from agricul- tural waste pollution. In California during 1960-1971 there were five documented fish kills of import- ance attributed directly to livestock opera- tions. During this period there were other fish kills ascribed to lowered dissolved- oxygen (California Department of Fish and Game, 1970, 1971), but it is not known what roles livestock operations might have had in reducing the oxygen contents of streams. Although livestock- related fish kills in California have been infrequent, care must be taken to insure against their reoccurence. Plant nutrients in relation to eutro- phication. Nitrogen and phosphorus are the two plants nutrients whose concentra- tions in natural waters usually determine amounts of aquatic plant growth. They are always available to some degree in surface runoff water and in water from most underground reservoirs. Drainage from animal wastes can be expected to increase the amounts of these nutrients in surface runoff. When temperatures are favorable, turbid green proliferations of algae and other aquatic plants in normally clear water are the usual visible signs of nutrient enrichment and eutrophication. Rates of eutrophication of lakes or reser- voirs are usually directly related to rates of acquisition of plant nutrients, and many of man's activities in the countryside result in increasing rates of eutrophication of water bodies. Nutrient enrichment pro- ceeds naturally in moving waters and in lakes, however, as a result of soil weather- ing and erosion processes. Lakes of recent geological origin started to age as soon as glacial ice melted. Natural additions of nutrients increased primary and secondary productivity and the lakes slowly acquired sediments. Many ice-age lakes evolved into marshes and, eventually, into organic soils. In the U. S. alone, there are approximately 75 million acres of organic soils that once were beds of shallow lakes. A large propor- tion of these soils have come into being since the last ice age. Man's use of waterways and water bodies for waste disposal have featured prominently in speeding up eutrophica- tion — a noted example is that of Lake Erie, which in the last 15 years of accelerated eutrophication is presumed to have aged the equivalent of 150 years of natural aging. Nitrogen and phosphorus are sometimes added . intentionally to low-fertility lakes in order to increase fish production, but excessive nutrient additions have also caused obnoxious forms of algae to reach nuisance levels (Smith, 1967). Restricted light penetration in algae-clouded waters is also said to affect fish production ad- versely (Eby, 1966) . Photosynthesizing plants in nutrient- rich waters eventually die and their re- mains create a biological oxygen demand. If the water body becomes anaerobic, fish kills and putrefaction will likely occur. Thus the aesthetic, recreational, and do- mestic-use values of water bodies may be- come impaired solely from additions of mineralized plant nutrients without in- volving organic matter additions from ex- ternal sources. Clearly then the entrance of animal manures, and of nutrients derived from them, into water bodies used by the general public should be kept within limits 47 compatible with prevention of wasteful damage from excessive growth of algae. Nitrate and nitrite hazards to man and livestock. Concentrations of nitrate in municipal drinking water supplies are monitored regularly by public health ser- vices because nitrate is the precursor of nitrite implicated in the rare disease known as infantile methemoglobinemia or "blue-baby disease" — so called because of the blue tinge of an affected infant's skin. The discoloration is due to formation of abnormal amounts of methemoglobin when more than the normal amount of ferrous iron of blood hemoglobin is oxidized to the ferric form. A nitrate-nitrogen concentra- tion of 10 parts per million (45 parts per million nitrate) has been set by the United States Public Health Service as a permis- sable nitrate-nitrogen level in public water supplies. In California, the permissable level is 20 parts per million of nitrate- nitrogen. Infantile methemoglobinemia has not been reported in California although special attention has been given to search- ing for such cases. Infantile methemoglobinemia, first linked with nitrate in well waters in 1944, is nearly always associated with shallow, rural wells. In the U. S. there have been no reports of fatalities from well water nitrate during the 15-year period from 1952-1966 out of about 40 cases of infantile methemoglobinemia re- ported (Bailey, 1966). In 1972 the Na- tional Academy of Sciences, which was reviewing nitrate and nitrite hazards to livestock and man, communicated with 13 state health departments, and these agen- cies reported about 10 cases with no fatal- ities for the period 1960-1969 (Natl. Acad. Sci., 1972). Livestock deaths ascribed to nitrate in manure-contaminated shallow ponds are not infrequent- -the toxic level is con- sidered to be about 500 ppm nitrate. When animal manures are spread on fields or pastures having low spots, rains can wash manure and dissolved nitrate into these depressions and evaporation will increase nitrate concentrations. Therefore, animals drinking from the spots risk nitrate poison- ing, particularly if temperatures arc favor- able for rapid biological conversion of the nitrogenous components of organic resi- dues to nitrate. Nitrogen balances of open water boles are highly dynamic and complex. If BOD is high, aeration is poor, and temperatures are high, nitrate concentrations may be- come very low because of denitrification. But if the organic matter contents, tem- perature, and aeration conditions are right for nitrate formation, nitrate buildup can be very rapid. Thus, animal deaths from drinking nitrated water in the field or open range may occur under conditions which have been known to carry livestock safely for many years. The problem of possible stock losses from nitrate poisoning on the range or in pastures is further complicated by the variable amounts of nitrate contained in forage. Certain climatic factors can, par- ticularly in early spring, cause increases in plant-contained nitrates which in turn can be additive to nitrate contained in animals' drinking water. For example, when plant growth is restricted due to low temperatures, overcast, or drought, nitrate is accumulated in plants because their roots continue to absorb nitrate from soil solutions even though photosynthetic ac- tivities may be insufficient to elaborate the absorbed nitrate into plant protein. Herbi- vorous animals are usually able to contend with large amounts of nitrate appearing suddenly in feeds and water holes, but with high stocking rates of domestic animals there are increased risks of exposure to nitrate overdoses in animal feeds and drinking waters in unprotected ponds be- cause of heavier manure deposits in and near water holes. Manure additions to surface and underground waters Beside entering surface waters through obvious routes, animal manures and ma- nure decomposition products can enter .underground waters by vertical drainage. Additionally, manurial compounds such as ammonia can enter surface water through volatilization and reabsorption of the volatile compound. Direct discharge into waterways. It was once common practice 1 to discharge 1 collected liquid wastes directly into a con- venient water, and souk 1 livestock opera- tions were located to take advantage 1 of such waste- disposal systems. Today, how- ever, there are few if any water bodies that can be u*c(\ for disposal of untreated manurial wastes from any source without causing concern to other people. Because 48 of increasing human needs for water and waste-water disposal, the view of disposal that once was exemplified by the saying, "One man's sewer is another's fountain," has given way to demands for water- quality standards, regulations, and en- forcement as practical measures for ex- tending the usefulness of available water supplies. Many states (California included) have specified standards for the quality of water that may be discharged into streams by water users. The federal government has also recently invoked old laws governing discharges of wastes into navigable streams and their tributaries. Alternatives to direct discharge of wastes. To the extent that aqueous meth- ods of manure handling are used, beef, poultry, and swine-production units, and dairies in pa.ticular, must regularly dis- pose of large volumes of contaminated waste water. Compliance with laws re- stricting discharge of liquid wastes into water bodies calls for increased use of the land as a natural sink for moderate ap- plications of manurial nutrients and or- ganic matter. In the past, dairies were usually integrated with pastures that re- ceived the manure generated by the dairy, but today higher water use associated with automated pre-milking washing systems for liquid transport of manure, importa- tion of feed, and increased numbers of cows per dairy have increased the stress upon disposal capacities of pastures di- rectly associated with milking operations. Successful waste-control operations (in terms of economics and adequacy) of modern dairies in California appear to be favoring holding ponds as integral parts of waste water management systems where liquid wastes are to be spread upon ad- jacent land. Holding systems offer both operational flexibility and nuisance con- trol during storage. Some investigators have gone into con- siderable detail in designing and testing lagoon treatment systems (Loehr and Agnew, 1967; Loehr, 1969) and measur- ing the effects of such systems on manure degradation (Loehr and Agnew, 1967). These studies have shown that effluents from such anaerobic, aerobic, or combi- nation lagoon systems were still not suit- able for direct discharge into receiving waters. Many California livestock pro- ducers have reached similar conclusions and have installed facilities designed as holding ponds rather than lagoons (Meyer and Baier, 1971) . It should be emphasized that holding tanks and ponds, and other manure-storage facilities, still require ade- quate land per animal to accommodate the eventual use of the liquid manure. Swine producers were among the first to try water flushing systems for removing manure from pens and swine-houses, and of the few true lagoons operated in Cali- fornia, most are associated with swine- production units. Some egg-producing units in California are also using water to flush and transport chicken manure into holding-pond storage systems. Beef-cattle producers have also followed the trend toward confined animal quarters and hydraulic systems for handling ma- nures. Slotted-floor systems pioneered by the swine industry have been adapted for beef cattle in some instances. Volumes of waste to be handled from a common beef- cattle feeding operation are usually many times greater than from an economically- sized dairy, so holding-pond systems have been less popular for beef animals. In Ontario, Canada, where feedlot oper- ations are generally smaller than those in California, lagoons are more common. Al- though microbial activities in these Cana- dian lagoons reduce pollution potential of animal wastes by decreasing BOD, lagoon effluents may still be sufficiently active biologically that these lagoons are often operated as holding ponds (Townshend el al„ 1970). Townshend et al. (1970) also reported that effluent from an over- loaded lagoon was responsible for a fish kill, and that overflow from a manure storage tank adversely affected the quality of an adjacent private well. Although lagoons are satisfactory for holding and for partial treatment of ani- mal wastes, they usually do not perform as an equivalent to an engineered sewage treatment system (Loehr and Agnew. 1967). Even though BOD is reduced by microbial activities during impounding, it is a common view that high-nutrient-con- tent effluents should not be dumped into streams and that the nutrients belong on croplands. Runoff from barnyards, corrals, feedlots, pastures, and rangelands. Manure and manure decomposition pro- ducts readily transportable in surface run- off can become major sources of stream 49 pollution, but management can minimize nutrient and organic water contamination of runoff water. Climatic conditions, topog- raphy, and lot design influence the quality and quantity of runoff from confined and pastured animal facilities. Rangeland and pastured animals are least likely sources of stream contamina- tion, since pastured-animal production systems cause an over-all net export of nutrients from the grazed ecosystem. The waste-nutrient absorption capacities of pasture land usually exceed the amount of nutrients voided by grazing animals, even though grazing animals gather nutrients from a broad area and concentrate them into spots as urine or fecal droppings. Since unconfined animals often void them- selves near or in streams and other natural water bodies where they obtain drinking water, nutrients contained in their urine and feces are moved closer to lakes and watercourses. Direct elimination of wastes into or close to a waterway by high con- centrations of domestic animals can be an important concern, and Davis and Bunten (1969) and Robbins et al. (1971) have recommended that restrictions be placed upon animal access to streams. Statutes to that effect have been suggested in some states. However, the animal access to drinking water varies so much from place to place that such statutes should take into full consideration the relation of wild and domestic animal wastes to the ecology and intended uses of waterways. More obvious localized sources of ma- nure and its byproducts in runoff waters are such high animal-density corral areas as barnyards and feedlots (Loehr, 1970; Townsend et al, 1970). Amounts of run- off from these are functions of rainfall distribution and intensity, lot design and management, and climatic conditions such as freezing and thawing. In general, water contamination from feedlot runoff is more of a problem in humid areas (Viets, 1971) than in the arid and semi-arid areas of California's major animal agriculture regions. But storm intensity, seasonality (whether snow or rain), and frequency alter the polluting effect of runoff from different areas and at diffen tit times. For example, some nor- mally dry areas occasionally have "flash- floods'" of short duration but high-inten- sity. Several authors have reported on effects of climatic conditions in relation to feedlot runoff under natural conditions: Grub et al, 1969a, b; Gilbertson et al, 1970. Others have made studies in the field under simulated conditions: Miner et al., 1966a, b; Swanson et al., 1971. Yet other work has been done in the laboratory: Keeton et al, 1970. Most of this work has been done in the midwest and, to some extent, in the southwest. Runoff from a corral will not occur until the moisture content of manure ac- cumulated on the corral floor, plus added rain, reaches the moisture-holding capacity of the manure. In one laboratory experi- ment, Keeton et al. (1970) found that the water-holding capacities of beef-cattle manure ranged between 0.44 and 0.83 inches of rain per inch of manure when water was sprinkled on manured soil col- umns at the rate of 1.5 inches per hour, with excess water being allowed to run off. Initial water contents of the manure as collected for their wetting and runoff ex- periments ranged from 7.3 to 28.0 per cent. When these manures became saturated at 60 per cent moisture the artificial rainfall yielded 100 per cent runoff from the pack. Gilbertson et al. (1970) also concluded that moisture-saturated lots were more con- ducive to runoff. However, Grub et al. (1966a, b) noted that dry, tight, com- pacted lots would yield more runoff than those which had been previously wet, and that moist feedlot surfaces could store significant amounts of water in the surface layer where dry manures were hydro- phobic and only slowly wettable. Ap- parently, less rain is needed to induce run- off from either very dry or very wet corral surfaces than from moist surfaces. Mois- ture is one of the significant variables that feedlot managers can control by varying stocking rates, cattle rations, and sprin- kling regimes. Cattle-hoof indentations (Miner et al., 1966a; Clark and Stewart, 1972) and "manure dams" formed by the activity of the animals (Gilbertson et al., 1970) are two of a corral's physical character- istics which reportedly influence rain- fall-runoff relationships. Lots having con- crete or other impervious surfaces may shed more runoff than non-surfaced lots, not only because of their impervious sur- face but also because the irregular inden- tations of the latter will hold more water that can evaporate or penetrate into the 50 3.0 2.0 1.0 0.0 0.0 1.0 2.0 PRECIPITATION Miner ef. al. (1966 a) dirt corrals, estimated from data concrete corrals, estimated from data Manges ef. al. (1971 ) Gilbertson et. al. (1970) Swanson et. al. ( 1971 ) Clark and Stewart (1972 3.0 4.0 inches Fig. 21. Relationships between rainfall and runoff from corral surfaces. The lines shown were drawn from actual experimental points by using statistical methods. soil (Miner et al, 1966a; Grub et al, 1969a, b ; Keeton et al, 1970) . Despite the various conditions, locations, and methods used in the aforementioned experiments on rainfall-runoff relation- ships, there is general consensus that from about 0.22 to 0.5 inches (average = 0.32 inches) of rain must fall before runoff will start; and that straight-line graphs (fig. 21) can describe rainfall-runoff rela- tionships of corrals. Climatic conditions, lot design, and management also affect the quality of run- off from animal-confinement facilities. Us- ing simulated rainfalls on 2 per cent slop- ing feedlots, Miner et al. (1966a, 6) noted that the concentration of manure byprod- ucts in runoff water was related to manure solubility, contact time with the runoff water, and physical transport processes exhibited by runoff flow patterns. Con- sequently, their values for COD, ammo- nium-nitrogen, nitrate-nitrogen, and sus- pended solids were correlated positively with temperature for sample collections taken in summer, fall, and winter. Their hypothesis that manure solubility would increase with temperature held true. Gil- bertson et al. (1970), monitoring actual rainfall-runoff events at some Nebraska feedlots, found that manure solids in "win- ter" runoffs of late February and early March were ten times more concentrated than in runoff from summer rainstorms. However, the winter runoffs included the spring thaw and the winter's accumulation of feedlot litter was thus washed from the lot in a fresh state, having been preserved for 3 months at freezing and near-freezing temperatures. The effect of the ambient temperatures upon rates of runoff in this case was judged to be subordinate to the effects of surface physical conditions. Moist lot conditions which favor bacterial growth for longer times may increase the BOD, soluble phosphorus, and soluble nitrogen contents of runoff from corrals (Miner et al., 1966a, b; Manges et al., 1971). Duration and intensity of rainfall affect both total amounts and concentrations of pollutants in corral or feedlot runoff. Con- centrations will initially increase with time as water from farther reaches of the lot contribute to- runoff strength, but pro- longed moderate-to-heavy rains will cause channels through the lot and thus mini- mize transport of material (Miner et al. 1966a) . Chemical changes in runoff from a feedlot exposed to an extended artificial rainfall of 0.2 inches per hour intensity have been monitored by Swanson et al (1971) who found that ammonium- and nitrate-nitrogen concentrations in the runoff dropped rapidly during the first hour. After several hours of no rainfall. 51 another rainfall again produced high run- off ammonium-nitrogen concentrations; this was due to interim activities of micro- organisms mineralizing organic nitrogen in manure. Nitrate was not produced as rapidly, and concentrations of nitrate- nitrogen were still low during the second period of runoff. Concentrations of pollutants in corral runoff water apparently decrease as rain- fall intensity increases until rainfall in- tensity is sufficiently high to generate turbulent transport of corral solids. Like- wise, corral slopes greater than 8 per cent cause turbulent transport of manure solids and increase runoff water strength. Lesser slopes apparently have little effect on run- off water quality. Of all design and management variables affecting feedlot runoff water quality, feed- lot surface material is the most influential. Grub et al. ( 1969 a, b ) found a higher concentration of BOD in the runoff from concrete-surfaced feedlots than from dirt lots. Miner et al. (1966o) also noted that runoff from surface lots con- tained higher concentrations of solids, COD, and Kjeldahl-nitrogen (fixed-nitro- gen including mineral plus organic forms of nitrogen as determined by the Kjeldahl chemical method). In addition, the per cent of solids analyzed as "volatile" when subjected to ignition temperatures were higher for surfaced lots (75 per cent vol- atile-solids) than for dirt lots (39 per cent volatile-solids). Swanson et al. (1971) speculated that the low volatile-solids ver- sus total-solids concentrations (30 to 40 per cent volatile-solids) from their un- surfaced test lots were due to transport of non-combustible soil material in the runoff along with manure. Grub, et al. (1969a, h) examined the effect of various rations on runoff water quality. Different rations produced runoff of varying qualities, but results were in- consistent and difficult to explain. Although effects of depth of manure accumulation on runoff quality were not apparenl in studies made by Gilbertson et al. i L970), Miner et al i 1966/;) noted tli.it the runoff water quality from a lot 2 weeks after cleaning and restocking was i concentrated as that from a longer- stocked lot. Leaching of contaminants from confined animal units and barnyards. Considerable quantities of potential water contaminants are initially available in manure or are released during decompo- sition of manure; these can be leached down into groundwater with sufficient ap- plied water. Problems of groundwater con- tamination can be more frustrating than those of surface-water pollution because of the relative inaccessibility and slow rates of turnover of underground reser- voirs which make their regeneration dif- ficult. The current focus of interest and re- search upon nitrate contamination of groundwater is related to health consider- ations of man and livestock. Salt buildup in groundwater is becoming of great con- cern in irrigated agricultural areas, par- ticularly in the southwest. Objectionable odors, color, or taste in groundwaters may also make w r ell waters undesirable for drinking purposes. Leachates from areas with accumulated manures have potentials for imparting any or all of these undesir- able qualities to groundwaters, depending upon loading rates and hydraulic conduc- tivity of underlying soils. Contamination of shallow groundwaters with manurial seepage and leachates have given rise to sanitation problems ever since man tapped these waters with shallow hand-dug wells. The problems became more serious as the numbers and density of livestock increased, but sanitation risks have diminished as tightly-cased drilled wells replaced the shallow wells of rural areas. After a report by Comly (1945) on nitrates in well water being associated with methemoglobinemia, several samples from shallow hand-dug wells in permeable glacial drift in Michigan were sent to the U. S. Geological Survey for analysis (Deutsch, 1963). Leachates from human and animal wastes were thought to be responsible for the high nitrate values found. High nitrate in well water was corre- lated with livestock operations (r = 0.58) in Missouri (Smith, 1965). Livestock op- erations were thought to be a major, al- though not the only, source of well-water nitrate in thai area of loess and limestone geology. In a study of nitrate movement below one level feedlot in Missouri, Smith il ( )o7) found thai nitrate concentrations decreased after 200 to 300 Eeet of lateral movement. The movement of nitrate from one Canadian barnyard used for manure storage for 50 years was definitely in the 52 direction of the bedrock slope (Gillham and Webber, 1969). Nitrogen concentra- tions had spread out from the lot, with as much as 5 parts per million nitrogen appearing in underground water 600 feet away from the lot in the direction of underground flow. Here, the water table was at 8 feet and bedrock started at 16 feet below the barnyard surface. More attention is now being given to incremental amounts of nitrate, salts, and other contaminants that can pass below the root zones through porous soils to deep water tables over periods of several years, decades, or centuries. From intensive core sampling of the Middle South Platte Val- ley of Colorado, Stewart et al. (1967a, 6) found less nitrate near the surface of corrals and more nitrate in the deeper soil profile beneath corrals than beneath cropped or uncropped fields. The generally low nitrate concentrations at corral sur- faces varied considerably but were indic- ative of denitrification processes predom- inating, and observed redox potentials of less than -330 millivolts offered support for this assumption. In a similar study of the Chino-Corona Basin in southern California, Adriano et al. (19716) noted that nitrogen and salts were higher in the unsaturated zone under dry-lot dairy corrals than under croplands or pastures. The high population of cows in the region insures heavy applications of manures over most of the dairy acreage in the basin. Studies of soil borings taken from feed- lots and adjacent lands in several regions of California ( Algeo et al., 1972 ) indicate that nitrate and chloride concentrations decreased rapidly with increasing depth. Although concentrations of nitrate and chloride in the first 4 feet beneath the feedlots were usually higher than in soils from adjacent fields of unspecified his- tories, differences were generally insig- nificant at depths below 4 feet. Olsen et al. (1970) in Wisconsin compared inorganic nitrogen contents and concentrations in shallow soil profiles down to 7.9 feet (240 centimeters) below uncultivated and cul- tivated fields and barnyards. Nitrate was higher in cultivated soils than in corral soils, and both contained higher nitrate than did uncultivated controls. Ammo- nium-nitrogen was low in cropped and uncultivated soils, high in well-drained barnyard soils, and exceedingly high in poorly-drained barnyard soils. Any considerations of the effects of feed- lot leachates on quality of underlying aqui- fers must take into account both the rel- ative acreages in feedlots as compared with other agricultural uses, and the gen- erally lowered hydraulic conductivity of compacted soils in feedlots. Although leachates from corrals can be heavily con- taminated and should be controlled, exten- sive pollution of aquifers probably does not occur from feedlots because they com- prise only a small fraction of the total area in a particular agricultural region (Stewart et al., 1967a; Olsen et al, 1970; Adriano et al., 19716). For example, the ratio of irrigated cropland to corrals was 13 to 1 in the Chino-Corona Basin study (Adriano et al., 19716) and over 200 to 1 in the Platte River Valley study (Stewart et al., 1967a) . However, farm barnyards have been implicated as local sources of ground-water pollution for rural families (Stewart et al, 19676; Olsen et a/.. 1970 1 . Volatilization and reabsorption of ammonia. A considerable proportion of the nitrogen in urine is in the form of urea from which ammonia (NH 3 ) is readily released by enzymatic decompo- sition. Some of the other organic nitro- gen compounds in feces and urine can be mineralized quickly to ammonia or to ammonium (NH|) ions. All ammonium- nitrogen is subject to volatilization as am- monia gas under alkaline or drying con- ditions. Stewart (1970) found that 85 to 90 per cent of nitrogen applied as urine was lost as ammonia under simulated con- ditions of a feedlot whose surface was al- lowed to dry before more urine was added. Local atmospheric nitrogen enrichment with distillable nitrogen volatilized from animal production facilities has been the subject of two recent investigations (Hut- chinson and Viets. 1969: Luebs et al.. 1973 ) . After they had measured the amount of ammonia trapped by dilute sulfuric acid and water in Colorado. Hut- chinson and Viets ( 1969 I concluded that ammonia volatilized from feedlots con- tributed significant amounts of nitrogen to surrounding surface waters. Yearly ab- sorption of ammonia in one trap located 0.4 kilometers from a 70.000-head lot was calculated to be 73 kilograms per hectare each year. 20 times the normal expected for that area. 53 Luebs et al. (1973) detected atmos- pheric ammonia by measuring distillable nitrogen caught in dilute acid and water traps. Nitrogen concentrations in such traps placed throughout the intensive dairy area in the Chino-Corona region reflected average cow density around the traps. They found a weekly maximum of 8 mil- ligrams distillable nitrogen per square decimeter of acid surface in an area having a cow density of 3,210 head per square kilometer. These values translate into 370 pounds of ammonium-nitrogen caught yearly per acre of dilute acid sur- face for a stocking rate of 13 cows per acre; amounts caught by water surfaces average only about 60 per cent of that caught by acid surfaces (Hutchinson and Viets, 1969; Luebs et al, 1973) . The dair- ies occupied about 150 square kilometers, but about 560 square kilometers were being affected with some atmospheric ni- trogen enrichment. Volatilized ammonia could possibly be transported to other areas in rain and fog and precipitated on vegetation or other surfaces, and amounts of nitrogen thus deposited could be significant or insignif- icant depending on the localized cycle of nitrogen in an area. Such nitrogen addi- tions, while possibly adding to the eu- trophic potentials of adjacent open waters, could benefit growing crops. Minimizing water pollution through feedlot and barnyard management Initial location of an intensive livestock operation is a prime determinant in its subsequent pollutional potential. Compro- mises in choosing the initial location of a feedlot may complicate management pro- cedures necessary to minimize the oper- ator's concerns about environmental im- pacts. Fairly level areas away from streams, having light precipitation and where the soil is only slowly permeable, constitute the better physical aspects of locations for animal-confinement systems. However, feed lots have to be located according to economic realities of the time and place, and with due consideration for prejudices as well as practicalities. Pos- sibilities for efficienl manure managemenl should he a prime consideration in choos- ing a new feedlot location. The location itself will help determine what manage ment principles can best be applied to existing lots. Potentials for water pollution from corrals and barnyards can be reduced by water management. Roofed corrals, though expensive, can prevent runoff from manured areas (Turner and Proctor, 1971). Runoff water originating outside the feedlot can be diverted from passing through the lot or manure storage areas by arrangements of dikes. Such diversions may relieve pollution potentials of a feed- lot by as much as 50 per cent (Madden and Dornbush, 1971). Properly con- structed and maintained dikes and hold- ing ponds will detain polluted runoff from corrals and manure storage areas, and will prevent slug-loads of polluted water from entering streams (Gilbertson et al., 1970; Loehr, 1970; Dale, 1971). Feedlot runoff water has been used for crop irri- gation (Koelliker et al., 1971; Manges et al., 1971), and also has been metered slowly into a large stream where legal and other conditions have permitted (Miner etal, 19666). Grassed areas have been used to ame- liorate runoff water quality. Edwards et al. (1971) found that nutrient and BOD levels in barnyard runoff were reduced after runoff was subjected to dilution, settling, screening, and infiltration pro- cesses along a 500-meter grassed effluent ditch. However, the remaining nutrient concentrations still exceeded algal bloom limits of the area. Weidner et al. (1969) compared several small watersheds and found that runoff from meadows had almost no pollutional characteristics. Rohbins et al. (1971) have suggested that to reduce manurial pollu- tion there should be grassed areas be- tween sources of manurial runoff and streams into which runoff might otherwise flow. Theoretically, the* feedlot operator should he able to manage corral surface moisture to reduce runoff quantity and improve runoff quality while still prevent- ing infiltration of pollutants. A slightly moist surface with little slope will absorb light rains and decrease runoff. Manure mounds and designed slopes allow heavy rains to run off to detention ponds and prevent sloppy areas which have, inci- dentally, been shown to decrease animal performance (Morrison et al., 1970). A little moisture will also allow a tighter 54 packing of the surface that essentially prevents infiltration. Manure will also stabilize and decrease in volume (on-site composting) under these moist, layered conditions (McCalla and Elliott, 1971). Moisture on a lot can be varied by adjust- ing animal densities and by artificial sprinkling. In many respects, a moist, compact cor- ral resembles the "Barriered Landscape Water Renovation System" (BLWRS) proposed by Erickson et al. (1971) as a means of removing some pollutants from liquid animal waste. In the Erickson sys- tem the surface of the disposal area is kept moist and aerobic to encourage conver- sion of applied organic nitrogen to nitrate- nitrogen, whereas the subsurface is de- signed to provide an anaerobic zone with restricted drainage where nitrates are de- nitrified and volatilized as free nitrogen (No) and oxidized nitrogen as nitrous oxide (N 2 0) gasses. Similarly, a moist but aerobic corral surface with a subsur- face naturally compact from cattle stomp ing will encourage nitrification and sub- sequent denitrification of excreted organic and inorganic nitrogen (Mielke et al., 1974) . In such a corral most nitrate trans- ported in the limited water into the packed sublayer is lost from the system. Any ni- trate contributions to groundwater pol- lution should therefore be minimized or eliminated. Mielke et al. (1970) took core samples from a level Nebraska feedlot. The 1-foot- deep manure pack had reduced infiltration to 0.08 centimeters per hour and free water was often noticed on the surface. Nitrate-nitrogen, ammonium-nitrogen, and Kjeldahl-nitrogen concentrations dropped off with depth below the manure pack. Denitrification, as well as impeded water penetration, was implicated in the nitro- gen reductions as redox potentials were below 320 to 340 millivolts. Although the feedlot studied by Mielke et al (1970) was located over an aquifer recharge area and the groundwater varied from 2 to 7 feet below the surface, these authors could find little evidence of pollution of ground- water. Elliott and McCalla (1972) installed caissons in a beef-cattle feedlot to monitor and compare underground feedlot micro- bial activities with those of an adjacent cropped field. Unlike the soil-atmosphere beneath a cropped field which approx- imated the earth's atmosphere, the feed- lol soil gases were high in carbon dioxide and methane. As methane production only occurs at low redox potentials, any nitrate appearing in the /one of meth- ane production should be denitrified. Many California feedlots are located in dry climates, and Elliott and McCalla (1972) found that drought also reduced carbon dioxide and methane levels be- neath feedlots — this is perhaps another reason for keeping feedlot surfaces moist. In some arid areas of California the low rainfall (less than 6 inches) does not supply enough moisture to move nitrates below 3 or 4 feet, and Ayers (1972) sug- gests that sprinkling might leach the ni- trates farther. As Stewart (1970) pointed out, nitrates from manure decomposition will travel rapidly in wet but aerated soil. Research is needed to be able to predict conditions under which nitrate and other pollutants might be leached in California's various climatic regimes. Moisture man- agement can play a key role in reducing surface- and ground-water pollution from animal-production facilities once research provides answers to a few basic questions. Runoff and leaching of pollutants from land-spread manure Every watershed contributes some water contaminants to the surface or under- ground drainage. Natural processes, such as soil erosion and wild animal and bird defecation release nutrients, organic mat- ter, and bacteria to streams and lakes. Likewise, in areas where rainfall is suffi- cient to result in movement of water down through the soil, minerals will be carried with this leachate and thev eventually reach ground water. In certain areas of Missouri (Smith. 1965) and California (Stout and Burau. 1967). natural current and historic processes could account for high nitrate found in ground water. Robbins et al. ( 1971 ) in a study involv- ing several small watersheds, noted that ". . . the effects of animal wastes properly spread on the land are overshadowed by natural pollutants." In fact, improvement of vegetative cover with manure can have a beneficial effect on subsequent runoff quality. In an area having a rainfall of 70 to 80 inches per year, runoff and ero- sion were reduced on fallow and corn plots 55 by additions of barnyard manure (Neal, 1939). Minshall et al. (1970) found that nutrient losses and runoff quantities were less from plots where manure was incor- porated in the summer than from similar control plots. Incorporation of manure into the soil has proved to be the most effective way of preventing manurial nutrients and other potential contaminants from reaching riv- ers. Bartlett and Marriott (1971a) .devel- oped a method of subsurface incorporation of liquid slurry. Decreased contaminated runoff was touted as one of the system's many benefits. Reddel et al. (1971) , study- ing disposal of great amounts of beef manure by deep plowing, found that run- off quality of heavily-manured plots de- pended on resultant degrees of soil cover from plowing. Manure spread on frozen or snow-covered ground is subject to spring thaws without the benefit of soil contact and can release large amounts of nutrients in the runoff (Midgley and Dunklee, 1945) . Ten per cent of the nitro- gen, 6 per cent of the phosphorus, and 8 per cent of the potassium were lost from winter-applied manure in an experiment by Hensler et al. (1969). Minshall et al. (1970) found that such losses amounted to 20 per cent, 13 per cent, and 33 per cent, respectively, of the nitrogen, phos- phorus, and potassium applied. Manure applied at "disposal rates" (where nutrients are added in excess of what is lost by crop uptake, volatilization, fixation, and denitrification) can degrade the quality of both runoff from the area and leachate beneath the area. Excessive rates of manure application can result in losses of highly mobile nitrate by leaching (Webber et al. 1968; Martin, 1970; Bart- lett and Marriott, 19716; Koelliker et al., 1971). Guidelines for an area can be developed from data on crop growth and fertilization requirements, and from esti- mates on other nitrogen losses (Webber et al., 1968) . Manges et al. (1971) applied cattle manure at rates up to 241 tons per acre and found that nitrogen and salts accumulated in the soil surface while ni- trate-nitrogen was leached — most of the minerals remained in the top 27.6 inches (70 cm.) of the soil. Mathers and Stewart (1971) also applied high rates (up to 538 tons per acre) of manure to a soil, and noted that although some nitrogen was removed from surface layers of soil by crops considerable downward movement of nitrate (up to 360 centimeters) oc- curred. Eventual pollution of ground water from applications of manurial nutrients in excess of crop needs and other losses make this practice undesirable. Phosphorus added in manures is "fixed" in most soils (Martin, 1970), although soils do not have an infinite capacity to absorb and retain phosphorus (Goodrich and Monke, 1971). In general, phos- phorus from applied manure is not leached from soils. Some soils also have the ability to "fix" potassium (Martin, 1970) in the clay structure and thus prevent leaching. Potassium and other cations are also held on the cation complex of soils. Neverthe- less, heavy rates of applied nutrients can exceed soil adsorption capacities and will be leached. For productive use of manure on agri- cultural land, the goal of manure manage- ment should be to prevent manure from over-stressing the natural nutrient and organic matter capacities of soils and waterways. ANIMAL MANURES AS FACTORS IN DISEASE TRANSMISSION Dicscb (1970) states that more than 150 r "lock-jaw.") Concentrated animal populations are more conducive to the rapid spread of dis- ease, so close surveillance and rapid treat- ment of disease has become an increas- ingly important feature of animal hus- bandry. Factors in the spread of disease Diesch (1970) lias outlined six factors essential for the spread of disease (fig. 56 SOIL RESERVOIR (spores) CAUSATIVE AGENT >* t LARGE ANIMAL RESERVOIR DISEASE IN ANIMAL DISEASE IN MAN EXIT FROM RESERVOIR TRANSMISSION BLOWING DUST RESPIRATORY SECRETIONS VAGINAL EXCRETIONS MANURE EXCRETIONS BITING PESTS BITING PESTS DOMESTIC FLIES MANURE IN RUNOFF MANURE IN DRINKING WATER MANURE IN RECREATION WATER BLOWING DUST MANURE FERTILIZATION DIRECT CONTACT ENTRY INTO HOST I CONTAMINATED AND WATER INHALATION FOOD BODY OPENINGS- Udder, Uterus, Novel, Cutaneous abrasions, Etc. EXTERNAL MEMBRANES (Eye) Fig. 22. The six essential steps in the spread of disease via animal manure. 22) : Causative agent, reservoir of the in- fectious agent, mechanism of escape, mechanism of transmission, method of entry into new hosts, and susceptibility of the host. All of these factors must be present for a disease to spread. The causative agent can be a bacte- rium, virus, protozoan, rickettsia, fungus, or larger parasite. The host specificity of the organism will determine the potential for spread of the disease to other hosts. Only sick or, in some cases, "carrier" animals will release and proffer patho- genic organisms. Coliform and fecal coli- form bacteria, although not always patho- genic, may cause coliform mastitis and coliform uterine infections in dairy cows, and colibacillosis of calves which are major problems associated with manure contamination. Coliform bacteria have commonly been used as indicators of fecal contamination, and fecal strepto- coccus bacteria have recently been used as specific indicators of animal waste con- tamination. Animal wastes can also be differentiated from those of humans by using coliform: fecal streptococci ratios (Wadleigh, 1968; Geldrich and Kenner, 1969). As a general rule, this ratio is greater than 2.5 in human wastes and less than 1.0 in animal wastes. Because of different rates of survival of each specie, the ratio is best used as an aid in locating proximate sources of contamination. Pres- ence of fecal bacteria in food and water does not automatically indicate the pres- ence of disease-causing organisms, but does suggest a definite sanitary problem and potential for spread of disease. Most diseases spread in animal waste originate in a living animal (or man) because parasitic and pathogenic organ- isms grow and multiply in a living body. Certain spore-forming disease organisms. such as Bacillus anthraci (anthrax) and Clostridium tetani (tetanus), will easily survive the rigors of the outside environ- ment for indefinite periods, and contam- inated soil is a reservoir for such organ- isms. Free-living soil microorganisms such as those associated with coccidioidomycosis and histoplasmosis, which can also attack man. are nourished by nutrients supplied by animal wastes (Decker and Steele. 1966) . The degree of exposure of animals and man to a reservoir of disease organ- isms governs the importance of that reser- voir in the progression of a particular disease. Escape routes of pathogenic organisms found in manure are not limited to fecal and urinary excretions. For example, va- ginal discharges infected with the Q fever organism, Coxiella burneti, or those caus- 57 ing brucellosis. Brucella sp., may contam- inate animal wastes. Respiratory aerosols containing pathogenic organisms, e.g.. Mycobacterium bovis (tuberculosis), may — though rarely — contaminate fecal waste. In addition, flies breeding in animal waste can carry pathogenic organisms from wounds of infected animals (including fly-induced wounds) directly to other an- imals or their feeds. For example, the face fly (Musca autumnalis) which breeds in cattle droppings and especially those of pastured cattle, is an important vector in the spread of pink eye disease ( Morax- ella bovis) in cattle. Hanks (1967) reviewed the transmis- sion of disease by flies and concluded that there is ". . . sufficient evidence of the link- age [between flies, waste, and disease] to condemn practices in the disposal of waste which permit fly propagation." Any pro- cedure which controls fly-breeding in an- imal waste will have the additional benefit of reducing exposure of surrounding an- imals and humans to disease. Gwatkin and Mitchell (1944) demon- strated that flies could occasionally carry Salmonella pullorum externally and in- ternally from contaminated feed to non- contaminated poultry feed and thus cause salmonellosis in chickens. Actual documen- tation of diseases transmitted by flies from feces to other animals or man are scarce in the literature. Although Faust et al. (1968) conclude that flies are common (but incidental) carriers of enteric path- ogens, Anderson (1966a) has stated that no diseases are transmitted solely by flies. The quantitative role of flies in the trans- mission of disease has received but little research. Direct contact with feces is a more common mode of transmission of disease. McCroan et al. (1963) reported eases of salmonellosis in young children who had been given chicks for Easter; intimate contact with the chick feces was the prob- able cause of the disease in the children. In England, cattle contracted salmonel- losis from grazing a pasture that had been spread with a manure slurry contaminated with Salmonella t\phimarium (Jack and Hepper, L969). Disease may spread when domestic animals come in contact with the feces of infected wild animals. Goyal and S i n <_' 1 1 (1970) found Salmonella anatum in the feces of farmyard poultry ana pigs and in the feces of rats, lizards. and sparrows associated with the same barnyard. In the U. S., widespread migration of rural families to cities has reduced the incidence of disease attributed to contam- inated drinking water. With a few notable exceptions, people served by monitored, chlorinated, and otherwise treated drink- ing water are relatively exempt from water-borne infections such as typhoid, cholera, hepatitis, and amoeba-dysentery. Paradoxically, the emphasis on water rec- reation in rural areas has increased man's exposure to water-borne diseases (Diesch, 1969). Schaeffer (1951) and Gillespie and Ryno (1963) have reported cases of leptospirosis in people swimming in water contaminated by farm animals excreting Leptospira pomona. Miner et al. (1967) detected Salmonella infaniis in feedlot runoff. Grazing and corralled farm an- imals were thought to be the major source of bacterial pollution in the Snake River (Anon., 19686), but it should be realized that wild animal populations can be an important source of bacterial contamina- tion of natural waters quite independently of domesticated animals. Unsanitary drinking water is still a prominent route of disease transmission between animals, but animal management can often alleviate disease problems. For example, Ogelsby (1964) investigated an outbreak of salmonellosis in a feedlot and found that cattle were drinking from a mudhole in the middle of the lot. Ex- amination of the fecal material from in- fected cattle and of the mud from the water revealed the presence of Salmonella typhi- murium in both. Diesch (1970) discusses the importance of water-borne transmis- sion of other bacterial, rickettsial, viral, fungal, and parasitic animal and human diseases that can be contracted from an- imal manure. Manure dust can carry disease organ- isms. Fungal diseases, notably coccidio- idomycosis, are prevalent in dusts of semi- desert areas, such as those in southern California and Arizona (Bridges, 1963). Other bacterial, rickettsial, and viral dis- eases can also be acquired from inhalation of infected dust or aerosols — psittacosis of poultry and man and Newcastle disease of poultry are viral diseases commonly spread in this manner. Henderson (1969) re- ported one instance in which the spread of foot-and-mouth disease virus was attri- 58 buted to air-borne aerosols or particulates. If all infectious agents survived the trip from one host to another, many diseases would be pandemic throughout animal and human populations. Fortunately, few dis- ease organisms are able to effectively cope with the competition and changing envi- ronments of the world outside their host. The paucity of data on survival time of pathogenic organisms in common manure- handling systems and climates is surpris- ing. The limited information on the sur- vival ability of some common pathogenic organisms found in manures was empha- sized in a review article by Diesch (1970) . Kuzdas and Morse (1954) found that Brucella abortus survived 1 day in bovine urine at 37°C, but died off more repidly in feces; cooler temperatures increased the survival rate. McCoy (1967) tested surviv- al of E. coli, Streptococcus faecium, and S. bovis in an aerated cattle manure slurry. E. coli grew initially but died out after 5 or 6 days. S. faecium died out at about the same rate, and S. bovis could only survive for 2 days. Diesch et al. (1970) found that leptospires could last in an oxida- tion ditch for up to 18 days. Gibson (1967) determined that of the organ- isms which he tested only salmonella, anthrax, and Johnes disease organisms cculd survive the common slurry system and remain alive when manure containing them was spread upon pastures. Once ap- plied to pastures, the anthrax and Johnes bacilli could survive indefinitely and sal- monella organisms could survive 6 to 12 months. Galton (1963) also estimated that salmonella organisms could survive up to 1 year after pasture application. Rankin and Taylor (1969) noted the gradual die-off of Salmonella dublin, S. typhimurium, Staph, aureus, and E. coli in one manure slurry. These were still detectable after 12 weeks in slurry. Brucella abortus could not be de- tected after 11 weeks. The colloidal character and microbial population of agricultural soils should ef- fectively inhibit downward movement of pathogenic organisms. In laboratory and field tests, McCoy (1969) found that the top 14 inches of a silt loam soil retained most of the fecal bacteria from manure applied at the rate of 5 to 80 tons per acre. A sandy soil was slightly less efficient in straining bacteria. Transmissions of pathogenic organisms are complicated by varying times of release from the host, by seasonal temperature and moisture condi- tions, and by concentrations of harmful organisms in excretory materials. Lepto- spires, for example, are excreted in the urine of infected animals for several weeks to several months (Gillespie and Ryno, 1963 ) , thus increasing the chance for pass- ing the infection on to other animals and man. Transmission of a disease agent from one host to another does not guarantee that the disease will infect the second host, because animals possess certain na- tural and acquired resistances to patho- genic organisms. With domestic animals, immunization programs have contributed greatly to disease control. Immunization of animals against anthrax, for example, has reduced the incidence of that disease dramatically and is the principal control method for leptospirosis. In this country, most children are immunized against teta- nus. The universal distribution of the tetanus organism, the intimate contact of most children with soil, and the frequency of skin abrasions would seem to demand such immunization. The few number of cases of tetanus in non-protected children indicates that some immunization is ac- quired, perhaps because of mild exposures from small scratches as a child grows up. Certain organisms pathogenic to one animal may not affect other animals; man is not a susceptible host for the virus causing hog cholera, for example. Among the numerous Salmonella species S. faecalis is common to man, and S. bovis is most often found in bovine and ovine animals (Cooper and Ramadan, 1955; McCoy. 1967; Middaugh et al, 1971). S. typhi (typhoid) and S. enteriditus serotypes paratyphi A and B are primarily adapted to humans (Middaugh et al.. 1971). S. typhimurium, on the other hand, passes freely between humans and other animals. Diseases transmitted in animal manures It is surprising that pathogens surmount all obstacles to transmission and infection and survive to cause disease, as some do. Table 15 lists the more common diseases that can be transmitted in animal manure to other animals or man. With the excep- tion of salmonellosis, the incidence of disease transmission from animals to man via contact with manure and other routes is on. the decline. However, the passage of 59 > ? 51 3 o ^ 3 OJ "O J= o 15 ~ E 3 O/j o c 1/3 ^ a OJj '.J C/5 c c c o W C .2 x> c u o oxj C c eg y Li Oil C o QQ 2 w o ~ $ o S 2 2 Oh U c a E E E 2 3 00 c E o c F U C u c c > 2 "O ^ 33 u > < c/3 c S ^ -C >: ■c -3 | -o a at aa ^ ■£■ 8 o -o $5 ^ s 3 ~ !< ^ !< !< CQQqQa *J U ft. Q 3 ■3 a 60 r*~i ^O sO so OS O — ' — ON on u OJ 00 00 or 3 T3 "O 0J CO 03 Li- 3 c O o c >. c o c o u c o o O o on 3 -a J2 is C o o 03 X! c 03 o 3 3 3 c 3 CJ c 1Z) o ^O S o O o3 u K 00 o c «s 03 03 03 > o u cz O O 1/5 o _^ -3 \3 ~ o3 to 'X3 o 00 u 1> on 00 C E c 03 s. U E E o 9J E o 3 03 3 E 1 O. o C r3 £ O .3 o E ^3 3 E O ■« 3 ts S o E c -a . T3 u .2 o o c c 03 C 3 3 03 3 03 3 < U U ^ S S 2 TJ __ c ca ^ t; fc o- ^ r| £ S, §. ;-. •S 2 ^ o ? D. ■~ D. -I | ^ §. s- .1 | ■2 on 1 X - £ fc. 1 "5, C V > c 1 R > £ =Q £ T 3 CO c« O en jr O o o c >^ on on 3 on E o "2 'on O 1 | •s O | V on .2 'on O '5 03 c ^ C X 03 o 03 on 0- '■5 w o 00 o a o en c i 03 o o -E L C L J o. a % X O H o o3 03 <- < § 03 00 Uh £ a. certain diseases between farm animals is on the increase. The more troublesome ani- mal afflictions include Johnes disease, coli- form infections of young animals, cocci- diosis, and stomach and intestinal para- sites. Animal wastes and disease prevention Current immunization and chemother- apeutic practices in the animal industry have helped control animal disease and disease pathogens. Decreased incidence of disease agents, in turn, reduces exposure of man and other animals to the disease. Continued testing and vigilance should reduce instances of some transmissable diseases even more. The use of chemotherapeutic agents for growth promotion has resulted in the emergence of non-pathogenic serotypes of bacterial species that are resistant to some of the therapeutic-"nutritional" drugs (Smith, 1962; Bromel et al, 1971). This resistance can be genetically transferred from non-pathogenic to pathogenic sero- types of a certain species (Bromel et al., 1971) . Because of the difficulty of control- ling resistant pathogens, the use of drugs helpful in disease control has been gen- erally discouraged for "nutritional" pur- poses. Basic sanitation procedures should be standard to every animal-production facil- ity. Routine health inspections and treat- ment or isolation of sick animals also reduces amounts of pathogens in animal wastes. Manure should be kept out of water intended for human or animal consump- tion and water used for recreation. Under- ground water supplies are usually pro- tected by filtering through layers of soil, but fissures or other routes of direct con- tact between surface and underground water that bypass the filtering action re- duces this protection. Manure from sick animals and from those carrying harmful organisms should be kept from contact with other hosts. More specific research is needed on manure storage and handling methods so as to develop the best methods to protect against the spread of disease. Use of animal manures as animal feeds presents different problems in disease con- trol than those caused by using manures as fertilizers or by animals manuring their own grazing areas. Direct feeding of ani- mal wastes increases exposure of animals 61 to any pathogens present in the original waste. Before the idea of feeding animal manures to animals gains general accep- tance by feeders, consumers and govern- ment agencies, the manures fed will prob- ably have to be certified pathogen-free and of known nutritional value, and this will require standardized processing. Caswell et al. (1972) have suggested fumigation of broiler litter with ethylene oxide or heating the litter to reduce bacterial count (and thus the disease potential) of broiler ma- nure. Shell and Boyd (1969) found that hot composting of sewage sludge could eliminate Salmonella newport, Candida albicans, and Ascaris lumbricoides organ- isms planted in the original sludge. Similar composting processes would probably be the most feasible and practical standard treatment of animal manures. PREJUDICES REGARDING USE OF ANIMAL MANURES In recent years, animal manures have suf- fered declining popularity in the highly competitive fertilizer market in spite of advantages of familiarity inherited from centuries of use in agriculture. At the same time, proponents of organic manures have criticized modern trends toward expanding uses of chemical fertilizers. The animal husbandryman has been left in the middle — puzzled by these conflicting attitudes but still faced with the economic realities of declining demands for animal manures. If animal manures are to reoccupy and maintain a firm position as marketable commodities in developed countries such as the U. S., it appears that better recogni- tion of their functions as fertilizers and soil amendments hold the only immediate promise for their general acceptance. Un- founded prejudices must be recognized and overcome. When livestock owners fed their ani- mals mostly from their own farms, ma- nures were usually returned to the forage- producing fields, thus solving problems of necessary waste removal while at the same time contributing to the fertility status of pastures and fields. When neighboring farmers having few or no animals wished to buy manures for fertilizer, a considera- tion of quality entered into the bargaining. For example, a "weedy" manure spread upon row crops might undo the work of careful cultivation, whereas application to pastures of origin would do little in the way of changing weed populations. I nnecessary, excessive, or poorly-man- aged applications of manure have some- times led to unsatisfactory results, and the manure itself rather than its misuse has received the blame. Cultural practices that use animal manures to advantage are be- ing studied at various Experiment Stations in order to delineate appropriate rates of fertilization with plant nutrients contained in manures. Results from well-planned field trials are respected by growers who may be thinking of taking advantage of ma- nures supplied as byproducts from animal- feeding industries. Trouble-free use of manures requires special attention to the following particular features. Esthetics and nuisances Nuisances commonly associated with ma- nure can be bothersome to the user of ma- nure as well as to non-user neighbors (pages 36-45). Reaction to nuisances and esthetic considerations is an individual matter, and each farmer should assess his own circumstances about the effects of manure spreading. Most farmers will agree that manure is part of a traditional and natural cycle that can be tolerated in the interest of maintaining supplies of food for human populations. Weeds. Weed seeds are common in some manures. They may enter the ani- mals system with its feed and then pass through the digestive tract, or they may be deposited into excreted animal waste by wind transport. Weeds in fresh poultry manure are scarce, as few seeds can sur- vive the grinding actions of gizzards of seed-eating birds and their attendant di- gestive processes (Harmon and Keim, 1934; Cooper et al, 1960). However, ma- nures from other animals may contain numerous viable weed seeds if the original feeds have been contaminated. Some po- tentially viable seeds are partially scarified while passing through digestive tracts of animals, and the germination percentage 1 ma) even be increased by digestive proces- sing (Harmon and Keim, 1934). Viable 62 seeds in fresh manures can he killed hy hot composting or aerobic stockpiling pro- cesses (Abbott, 1968; Beutel et al., no date). If manure and weed seeds carried by manure are buried deeply enough in the soil during field applications, the seeds may germinate but the seedlings may not be able to break through to the soil sur- face. Most weed seeds remain viable even when buried in soil for several decades (Harvey, 1959). Top-dressing of weedy manure after cultivation may create prob- lems requiring additional weed control action. Weed seeds added to farmland with manures may be insignificant in number when compared with weeds and their seeds already present in a field. However, ma- ures intended for sale as fertilizers should be managed so as to reduce weed seeds to at least less than nuisance levels if not to near-zero. Problems associated with over-use of manure Salts. Nitrogen has been the nutrient ele- ment traditionally valued and sought after in manures because it is usually the first growth-limiting plant nutrient to show prominent deficiency symptoms after soils are placed under cultivation. However, manures containing nitrogen always con- tain substantial quantities of phosphorus and potassium as well as calcium, mag- nesium, sulfur and other micronutrients and extraneous non-essential minerals. Nitrogen in fresh manures is biologically unstable and susceptible to losses during storage, whereas phosphorus, potassium, and other ash constituents are not lost as readily. Nitrogen losses in storage mean that relatively larger amounts of manure (including phosphorus, potassium, and other salts) have to be placed in the field in order to supply the same amount of avail- able nitrogen. Some students of plant nu- trition maintain that long-term cycling of animal manures back to the land has resulted in greater over-all benefits from the plant-available phosphorus and potas- sium rather than from the nitrogen carried by manures. Such views have merit be- cause nitrogen can be extracted from the atmosphere by soil microorganisms, where- as phosphorus and potassium have to be imported or weathered from the parent rocks from which soils are formed. How- ever, repeated heavy applications of ma- nure can, like any other phosphorus- or potassium-containing fertilizer, cause det- rimental soil and crop effects directly from accumulating amounts of salts, or indi- rectly by phosphate-induced zinc defi- ciencies or potassium-induced magnesium deficiencies. Successful manuring with or- ganic fertilizers requires knowledge and management in the same degree applicable to use of inorganic fertilizers. Most California manures contain from 5 to 10 per cent water-soluble salts. Normal to heavy applications of manure in humid areas of the state would not be expected to affect plant growth adversely, as the salts would be effectively leached. Also. ". . . moderate but profitable rates" of manure applied in arid regions seldom cause crop damage (Abbott, 1968) — the soils and irrigation waters in these regions often contribute far more salts than are normally supplied by manures. Additional salt loads from manures may require more careful water management, but most growers in arid regions are conscious of the water requirements for leaching and take them into account in irrigation man- agement. Salt injuries to crops can result from loading soils with so-called disposal rates of manure (applications far exceeding reasonable crop needs). In pot trials and field tests in the high plains of Texas. Mathers and Stewart (1970, 1971) ex- amined grain sorghum and soil response to applications of up to 538 metric tons of cattle manure per hectare (240 tons per acre). Poor crop responses were ob- tained at application rates above 67 metric tons per hectare (30 tons per acre). Ac- cumulations of nitrogen and other salts in the surface were the two most readily noticeable results of these abnormally heavy manure applications. Manges et al. ( 1971) observed salt injury in corn grown in soils that had received 123 and 421 tons of manure per acre, and visible amounts of salts accumulated in these heavily- manured soils. Crop injuries, salt accumu- lation in soil profiles, and possible salt movement into ground waters militate against applying disposal rates of manure. Liquid from manure holding ponds, runoff catch basins, and manure lagoons may be sufficiently saline to require dilu- tion before use as irrigation water. At least one orchard in California has been deci- 63 mated by irrigation with effluent from a poultry manure holding pond. Dilution should be based on the electrical conduc- tivity (EC) of the pond, the quality of diluting water, and the EC permissable in irrigation water for the crop, soil, and cli- mate in question. Salinity of holding ponds will increase with surface evaporation and with recycling of the liquid as wash water. Different ratios of monovalent to diva- lent cations for a given salt concentration in the applied manure or liquid slurry will show different effects upon soil physical properties. A high proportion of monova- lent ions (sodium, potassium, and some- times ammonium) can increase soil dis- persion and decrease water penetration rates (Manges et al., 1971; Travis et ah, 1971). High potassium levels are common in animal manures and can be a cause for concern when manure is applied to some soils. However, calcium and magnesium contained in manures can cancel some of the deleterious effects of the monovalent ions. Questions are often raised about in- fluences that sodium chloride as a feed ad- ditive might have upon soil salinity when animal manures are returned to soils. Gen- erally, levels of additional sodium salts are much less than the sodium and potassium salts contained in feeds and waters and, consequently, in animal manures. There- fore, salts added to animal rations may not have a major influence in the over-all prob- lems of soil salinity. Nevertheless, sodium in animal manures is certainly of no bene- fit in terms of soil fertility or soil structural improvement. In addition, the need for adding additional sodium in the feed of beef animals has been questioned from a nutritional aspect (Morris and Gartner, 1971). Sodium chloride additions to ani- mal feeds should be minimized within the framework of modern feeding programs. Ammonia toxicity. Small amounts of ammonia gas in the soil atmosphere will inhibit seed germination or restrict root development. Urea in animal manure can l»e enzymatically converted to ammonia in 2 to S days; the conversion rates are gov- erned by environmental factors affecting microbial activity (Salter and Schollen- berger, L939) and the amounts of urease enzyme that happen to be present. I p to ( )0 per eent of the urine-nitrogen, pri- marily urea, can he lost by volatilization on a feedlot surface (Stewart. L970). Con- sequently, unless animal manures are handled to preserve the urine-nitrogen or are applied to soil at high rates, there is small likelihood that ammonia would exist at concentrations high enough to do dam- age. Little harm to the crop from ammonia toxicity should result from manures from animals that excrete urea. Most of the nitrogen in poultry manure is in the sparingly-soluble forms of uric acid and other nitrogen-containing com- pounds (such as creatine) which release ammonia in a series of sequential enzy- matic decompositions. At moderate to heavy application rates of poultry manures containing uric acid, sufficient ammonia can be released during the first few weeks to severely damage plant crops (Hileman, 1971) . In order to avoid ammonia toxicity, poultry manures of high nitrogen content can be composted or applied to soils with allowance for an incubation period of sev- eral weeks. This allows for conversion of uric acid to ammonia and then to nitrate, which is normally non-toxic to plants. Eno (1966) recommends a delay of 4 weeks between the date of manure application and date of planting. Rapid drying of fresh poultry manure will preserve the uric acid and creatine compounds that can later decompose and release ammonia when moisture is supplied. Conversely, incubation of moist poultry manure for several weeks with subsequent drying will release most of the ammonia. The amount of ammonia gas existing in the root zone is not easily determined. There are still many unanswered questions about the critical ammonia concentration that will inhibit plant growth, and about the possible interactions of other com- pounds in poultry manure which may be harmful to growing plants. Composting or delayed planting after incorporation of poultry manure successfully ameliorates the toxic effect and should continue to be the most useful management tools for the grower. Nitrate in forage. Nitrate can accumu- late in souk' plant species when grown in media containing more than enough ni- trate-nitrogen to satisfy rates of plant protein synthesis. Levels of nitrate in for- age that will induce* nitrate poisoning of cattle vary from area to area and are de- pendent on Factors not as yet completely understood. However, concentrations of more than 0.3 per cent nitrate-nitrogen 64 on a dry-weight basis are frequently con- sidered to be dangerous to cattle. Manges et al. (1971) found that appli- cations of up to 241 tons per acre of cattle manure did not affect the nitrate levels in the subsequent corn crop. Mathers and Stewart (1971) found that nitrate levels in grain sorghum responded to manure appli- cation rates, with levels in plants grown on heavily manured soil exceeding the recom- mended safety levels. Nitrate concentra- tions in a fescue pasture were increased by the application of poultry litter (Wil- kinson et al., 1971). Forage producers should regulate manure applications as well as other nitrogen applications to min- imize problems of high nitrate in forage. They can also monitor nitrate-nitrogen levels in plant tissue used for forage to determine when and if a problem may exist. Adverse changes in botanical com- position of pastures. Application of ni- trogen from manure or other sources to a grass-legume pasture will favor the grass species and depress the legume thus result- ing in an eventual predominance of grass. However, legumes can benefit at a later date from the increased soil phosphorus from applied manure (McKell et al., 1970). Adverse changes in chemical com- position of pastures. The ratio of nutri- ents in an applied animal manure will affect the nutrient uptake of plants grown on manured soil. In addition, the absence or scarcity of legume crops which are rela- tively high in nitrogen, calcium, and mag- nesium, will further affect the chemical composition of mixed pastures. Watkin (1957) noted that sheep manure decreased the nitrogen, calcium, and magnesium con- tent of some clover-dominant New Zealand pastures, but increased the nitrogen and potassium and decreased the calcium, mag- nesium, and phosphorus contents of grass- dominant pastures. Thus an adverse K/ (Ca+Mg) ratio created by manuring pas- tures could generate conditions favorable for grass tetany, a hypomagnesaemic syn- drome in cows and ewes. Nitrogen and potassium fertilization are also thought to reduce the availability of forage magne- sium to lactating cows and to increase the incidence of hypomagnesaemic tetany (Kemp et at., 1961). Zinz deficiency in orchards. Contrary to typical reports of the efficiency of ma- nure in supplying zinc to deficient crops (Barnette and Warner, 1935; Grunes et al, 1961; Miller et al., 1969), continued heavy applications of manure have accen- tuated zinc deficiency in some California orchards (Beutel et al., no date). Chand- ler's (1937) summary of his findings indi- cated that, while inadequate zinc in or- chards was common on coarser California soils, the deficiency was rare on finer-tex- tured soil except where the orchards had been planted on old corral spots, other heavily manured spots, or old Indian en- campments — soils from such sites con- tained high potassium. Chandler was un- able to induce a zinc deficiency in one fine-textured soil with four annual applica- tions of horse-cow stable manure at 60 tons per acre or by adding potassium. Price et al. (1966) recommended treatment of in- cipient zinc deficiency before applying poultry manure to California orchards. Foliar zinc sprays are most effective. The once-popular practice of driving galvan- ized nails or glazier's points directly into trees has given way to use of zinc sprays or to direct application of zinc salts to soils. Zinc nutrition of orchards should be moni- tored especially close when heavy doses of rich manure are applied yearly. Trace element accumulations in soils. Essential plant nutrients including zinc, copper, iron, manganese, and boron are always present in animal manures. These trace elements resist leaching from soils and accumulate in upper soil-hori- zons. Where water available for leaching is limited in quantity or quality or where soil factors preclude adequate water move- ment, boron accumulation problems may appear. The other essential elements, iron, zinc, and manganese are usually regarded as beneficial. Because animal digestive processes restrict the utilization of these elements, animal manure often contains higher concentrations than the original plant feed. Feed additives such as arsenic, sometimes fed to animals for growth stim- ulation and disease prevention, show up in the animals' manure. Data on the sub- ject are rare (Manges et al., 1971), but heavy continuous applications of manure possibly could introduce undesirable quan- tities of heavy metals into soil. Overdosing a soil with extraneous non-essential metals is much less likely to occur with heavy applications of animal manures than with 65 sewage sludges that may carry metal salts of industrial origin. Cadmium, chromium, mercury, and copper components of mu- nicipal sludges disposed of on farmland are becoming causes for concern and de- hate, particularly with respect to cadmium. Borate compounds were used for fly con- trol in poultry manure many years ago and yearly manurial applications were responsible for increasing the boron con- tent of some soils from borderline boron concentrations to above the toxic level. This toxicity, most noted in southern Cali- fornia orange groves, discouraged use of poultry manure for some time. Currently, there should be little concern about this problem as borates are not used for fly control. Arsenic is sometimes fed to poultry and swine at low but continuous levels and is thought to be excreted in equilibrium after a few days (Overby and Frost, 1960). Arsenic in litter from chickens being fed typical amounts of organoarsenic did not affect the arsenic content of soil treated with poultry litter for 20 years. Crops grown on those soils were similarly unaf- fected. Highly impractical amounts (2,000 tons per acre or more) of such litter would have to be applied to soils to equal amounts already present in some soils from ar- senical pesticides, herbicides, or defoliant sprays. Even so, human health would not be affected from consumption of plants grown on such contaminated soils, as evi- dence indicates that arsenic in the soil will injure the plant before harmful quantities are absorbed (Williams and Whetstone, 1940). Copper is sometimes fed to swine as a growth-promotant. Many swine producers in the United Kingdom have been feeding high levels of copper, but little is known about its excretion and subsequent effect on soil and crops (Frobish, 1971) . Further studies on the heavy metal content of ani- mal manures and their effect on the soil seem warranted. Hormones in animal manure Interest in the cycling of natural and syn- thetic hormones through the feed, the ma- nure, and back to animals or man via the uptake by plants has been reviewed by Dinius (1971). Apparently, estrogenic compounds are excreted by hormone-fed and hormone-implanted beef animals for the duration of the anabolic activity in- duced by the hormone (Turner, 1956; Story et al, 1957; Callantine et al, 1961) . Nevertheless, the manure of the average dairy cow usually contains about five parts per million of natural estrogens, three times the concentration of synthetic estro- gens in hormone-fed beef cattle manure and thirty times the concentration in hor- mone-implanted beef cattle manure (Din- ius, 1971). When manure from these ani- mals is spread on the soil at 12 metric tons per acre, the amounts of estrogen added will be approximately 60 grams, 20 grams, and 2 grams per acre, respectively. The ultimate fate of the primary syn- thetic hormone, diethylstilbestrol (DES) in the feces of steers implanted with DES was examined by Hacker et al. (1967). Ten per cent manure was mixed with two sandy loam soils, and various vegetable crops were grown to maturity. One-third of the original uterotropic activity, as de- termined by standard biological assay using mouse uterine weights, was extracted from the slightly alkaline (pH 7.5) soil. No uterotropic activity could be detected in the slightly acidic (pH 6.5) soil. Of the various crops grown, only lettuce roots and radish leaves showed some uterotropic ac- tivity and the amount was slight. Summar- izing this and other studies, Dinius ( 1971) concluded that a 50-kilogram person would have to consume a minimum of 1700 kilo- grams of food per day to be affected by the hormones originating from manure used as a fertilizer. Consequently, estrogens in land-spread manure are not apt to cause any hazard to man or his animals. It should also be borne in mind that some plants contain naturally-occurring hormones which may adversely affect fer- tility of animaks (Curnow et al., 1948; Moule, 1961 ) or improve meat animal per formance (Oldfield et al., 1966). FERTILIZATION WITH ANIMAL MANURES Returning nutrients and organic matter to to provide nutrients for plant growth — is tin- -oil via animal manures completes the enhanced by such judicious returns of nil- ancienl and natural cycle on which all life trients. Economic as well as biological bene- depends. Soil fertility— the ability of a soil fits accrue from supplying nutrients orig- 66 inally deficient in the soil and then growing crops to take advantage of the increased soil fertility. The conservation of manurial nutrients seems especially desirahle in this period of developing concern for the con- servation of natural resources. The value of animal manures in supply- ing fertilizer nutrients for farm crops has been noted since the beginnings of agricul- ture when manured crops grew visibly bet- ter than those without. In recent years, numerous studies conducted in various parts of the world have examined nutrient- supplying power of animal manures by comparing growth or yields of crops with and without applications of manures alone and in combination with other fertilizers. Principally, three measures of the compar- ative effectiveness of manures have been reported in the literature: short-term yields, long-term yields, and actual nutri- ent recoveries. Short-term studies of yields are quite easy to perform and are, if proper attention is given to replication, useful to farmers. Long-term studies of yields ex- tend the data to include residual effects, beneficial or detrimental, which may show up only after several decades — climatic and other experimental variables are mod- erated over the long term. Relatively few long-term studies have been carried out however. Nutrient-recovery data can be obtained from these short-term or long- term studies if the necessary chemical an- alytical work is included for calculating plant uptake and other additions and losses of nutrients. Nutrient-recovery data can be used to identify nutritional benefits to crops grown on manured soils, and can also be useful for evaluating data on crop growth obtained in yield studies. All three types of studies depend upon comparing animal manures with inorganic fertilizers on the basis of equal amounts of speci- fied plant nutrients. Short-term yield comparisons Because nitrogen is commonly the limiting nutrient for good plant growth, the abili- ties of manures or chemical fertilizers to increase plant growth are often compared on the basis of different forms of fixed nitrogen. In experiments with sweet corn in the Coachella Valley of southern Cali- fornia, Tyler et al. (1964) found that ni- trogen in barnyard manure was only one- fifth as effective as that of ammonium sul- fate in increasing yields. However, con- siderable residual benefits of manurial nu- trients were noted in the fall crop after a spring fertilization and cropping. Herron and Erhardt (1965) noted somewhat bet- ter yield results for manure when sorghum was grown; they found that manure nitro- gen produced first-crop yields equal to 35 per cent of those produced by equivalent amounts of chemical nitrogen. Residual benefits of the manure decreased by about one half each year, but after 4 years the total 4-year increase in crop yields from manure nitrogen approached 71 per cent of the effectiveness of the inorganic nitro- gen. In pot trials with sorghum, Mathers and Stewart (1970) found that manure nitrogen was about 42 per cent as effective as ammonium sulfate in increasing yields. Wilkinson et al. (1971) found that in fertilizing fescue pasture with poultry lit- ter the manure was about one-half as effec- tive as ammonium nitrate in increasing forage growth. Poultry manure applied to a nitrogen-phosporus-deficient rangeland by Adolph et al ( 1969) and McKell et al (1970) gave forage responses not signifi- cantly different from equivalent amounts of inorganic fertilizer. Where manure has been applied to phos- phorus-deficient soils, crop responses have been generally similar to those from inor- ganic phosphorus fertilizers. For alfalfa on the southern deserts (May and Martin. 1966) and cereals in the central valley (Petersen et al., 1969), phosphorus in ma- nure produced yields equal to those pro- duced by equivalent amounts of phos- phorus in commercial inorganic phos- phatic fertilizer. Petersen et al (1969) noted residual phosphorus effects 2 and 3 years after the original manure applica- tion. Bertramson and Stevenson (1942) compared prepared organic phosphorus compounds with inorganic phosphorus in a pot trial using sunflowers and tomatoes. They found that calcium ethyl phosphate was equal to treble superphosphate in pro- ducing plant growth. Several authors have related the ferti- lizer value of manure to certain specified chemical fractions of manure. Gardner and Robertson (1946) found that yields of sugar beets produced by the soluble por- tions of nitrogen and phosphorus in ma- nure were equal to those produced by com- mercial fertilizers. In pot experiments with different grasses, Gisiger (1950) noted that soluble urine-nitrogen produced yields 67 < OC LU a z s. U. LU ^< Z d < f- Z g < 2 s < C/3 UJ < «5 3 c^ Increase stated as per cent of that for chemicals IS, at >> u Im c u sO o OO O ISj u ecJ -. o CO y= k. ft, oo o vO o Average increase in total produce per rotation]: 03 CI u c u 6. 6,231 7,263 first 10 years 4,024 5,891 Nutrients applied per rotationt 2 o r- ir> potash m o phosphoric acid o »n nitrogen ri o r- >/-. £ 3 C a. Plot 20 (manure) Plot 14 (chemicals) i * 2 « E 2 u u jz > U < equal to or better than those produced with inorganic nitrogen, but the nitrogen in full liquid manure (dung and urine mixed) was only about one-half as effec- tive as inorganic nitrogen. In Europe, liquid manure slurries ("guiles") com- monly applied to crops have been com- pared with commercial fertilizer as a source of nitrogen (Herriott and Wells, 1962; Herriott et al., 1963, 1965). These experiments showed that manure slurries were 44 to 84 per cent as effective as inor- ganic fertilizers. The probable high pro- portions of soluble nutrients could have produced these relatively high nitrogen ef- ficiencies. Apparently, the nitrogen in manures is about 20 to 50 per cent as effective as commercial fertilizer nitrogen in influenc- ing short-term yields of crops. In contrast, phosphorus contained in manures is gen- erally conceded to be as effective as acid- treated forms of inorganic phosphorus such as super-phosphate. Long-term yield comparisons Studies over a period of 50 to 150 years which compared animal manures with mineral fertilizers showed that equivalent yields can be sustained with either organic or inorganic sources of nutrients (Bunting, 1965; McCalla et al, 1970) although yearly quantities of nutrients supplied were usually greater in the manured plots. For example, Bunting (1965) estimates that nitrogen applied to crops in standard yearly applications of farmyard manure on farms near the Rothamsted Station in Eng- land amounted to 140 pounds per acre. This amount of manure nitrogen is higher than that usually supplied to crops in ap- plications of inorganic nitrogen, but is lower than that applied yearly on manured plots at the Station. The effectiveness of nitrogen in manure in sustaining crop growth for 50 to 150 years must be less than that of chemical fertilizer nitrogen, because long-term yields of crops from adjacent fields receiving nutrients from the two sources were similar only when total amounts of nutrients applied with manure were much greater than those applied in chemical form. Where crops are given similar amounts of nutrients in the form of manures or chemicals (tabic 16), there is notably less yield response to manure, especially during the first decade. With continued 68 application of manure, the cumulative residual effect of the slowly-available or- ganic nitrogen in the accumulating soil humus narrows the ratio of crop response between manured and chemically-treated plots. Figure 23 shows the characteristic slow release of nutrients from heavy appli- cations of manure. In the experiment at the Rothamsted Experiment Station, when 280 tons of manure were added at a rate of 14 tons per year the 20-year residual accumulation of manure continued to show an effect on crop yields for several decades after manure was withheld from the plots. After 40 years without further treatment, yield from plots previously manured for 20 years was still double that of the plots which had never been fertilized. Nutrient availability and recovery comparisons Availability of manure nitrogen. Nitrogen is particularly subject to trans- formations affecting its availability and thus its eventual recovery by a growing crop. In ammoniacal form it can be lost through volatilization under drying condi- tions, especially when the soil is slightly alkaline. Nitrate-nitrogen, the normal ni- trogenous end-product obtained under aerobic oxidizing conditions, can be leached beyond root zones. Losses of ni- trate through denitrification from anaero- bic zones in soils are probably common occurrences in agriculture; such losses are not restricted to organic fertilizers how- ever, because nitrogen applied in chemical form can undergo similar transformations. Differences in nitrogen availability be- tween manure and mineral fertilizer sources can be explained best by the rela- tively slow biological release of nitrogen from complex organic compounds present in manure. The microorganisms that de- compose manure demand a carbon-to-ni- trogen ratio of less than 15 or 20 in the substrate before ammonia can be split off and released from nitrogenous organic compounds in sufficient quantities for good plant growth. Low-nitrogen manures or those with considerable litter have carbon : nitrogen ratios much higher than 20, and microorganisms will draw temporarily upon mineralized soil nitrogen, with plant roots losing in the competition for avail- able soil nitrogen. Nitrogen immobilized during the decomposit* n of manures of CONTINUOUSLY MANUREO 1852 - 191 CONTINUOUSLY UNTREATED 1851 ~!9li Fig. 23. Residual effects of 14 tons of manure annually on long-term barley yields at the Roth- amsted Experiment Station. Yields are expressed relative to the yield of the continuously manured barley. (From Hall, 1917). high carbon content will be slowly re- leased at later times as organic carbon de- composes to carbon dioxide. Martin (1972) offered this type of immobilization and mobilization process to explain differ- ences in availability rates of nitrogen in low-nitrogen steer and dairy manures and high-nitrogen poultry manure. Experi- ments by Tyler (Martin, 1972) which mea- sured immobilization and release of nitro- gen from these manures in soils, supported Martin's (1972) suggestions. Portions of the organically-bound nitro- gen in manure that resist mineralization in the soil are complemented by residues from heavier yields of roots and crops growing on manured plots. Increased num- bers of nitrogen-fixing microorganisms may grow in the manure and residue sub- strates and contribute to the long-term soil- nitrogen pool. The percentage of applied nitrogen and organic matter recoverable from soil after continuous applications of manure for extended periods of time can be considerable (table 17). The portion of recoverable nitrogen that consists of crop residues varies with the crop (table 18), and in some cases apparent recovery can be greater than 100 per cent if the manure stimulates growth of nitrogen-fix- ing plants or free-living nitrogen-fix- ing microorganisms. Manure-nitrogen that becomes part of soil organic matter can provide small amounts of nitrogen for growing crops long after manuring is ter- minated. The slow release of nitrogen from manures has been suggested as an asset for sandy soils where leaching of mineralized nitrogen is a problem (Curley and Fair- bank, 1964). Considering the complexity of factors affecting the availability of nitrogen from manure in different soils, estimates of aver- 69 - D __ Cd 3 c C C c c __ •^ cd a> b (11 ■ — "o Si ? oc tt r~ sO r- r~ -T r- vo ^t- X fc rs fN m "3- r*^ «n ^~ NO x s= E * J C^ O. u Cu fc - < _• '5 > c o t; -2 C o^ o ir o — r*~i ^c in m vC vD rs ri v~ m r»" m r^ ro m c cd cd o E >> ^ C q q fN s -a o T3 E ■a E U > ^_^ E "E E Si K « , >% >. >^ >» u L U L U U >n in m 4 vC c o ^_[. ' ~ -o 1 ■c u c 'X c — T u "^ c c c o u E u. j X c ■ g c B ?3 u Cu c u. C/5 LU r C c o (7 • ~ — S c c cd 1 c7 c75 E c s S 3 o X X C Si r Si X a ^ C £ a; X cd X i/i c « a> ON 6 m U\ i — i CD J 3 a.E E | o o U U 70 Tabu; 18 NITROGEN RECOVERY FROM MANURE BY VARIOUS CROPPING SYSTEMS* Cropping systemt and soil treatment Recovery of nitrogen from manure and crop residuest Estimated nitrogen recovery from crop residues Difference actual nitrogen recovery from manure Continuous cropping with corn Continuous cropping with wheat Continuous cropping with oats 26.7 36.1 46.5 36.6 54.3 per cent 3.2 13.6 14.6 16.4 33.4 23.5 22.5 31 9 Five-year rotation corn, oats, wheat, clover, timothy: Limed 20 2 Unlimed 20.9 *From Salter and Schollenberger (1939). tFrom table 17. age nitrogen availability from manure can only be expressed in general terms as a range of recoverable amounts. Turk and Weidemann (1945) suggested that the ni- trogen in animal manures was about 30 per cent as available to plants as was nitro- gen in mineral fertilizers. Kesler (1966) quotes University of Illinois scientists as saying that as a rule of thumb 40 per cent of the nitrogen is available the first year, 30 per cent the second, 20 per cent the third, and 10 per cent the fourth. Kesler ( 1966) also feels that the nitrogen in swine urine is as available as that in mineral fer- tilizers, whereas organic nitrogen in feces is not readily available to plants. For poul- try manure, Robertson and Wolford (1970) estimate that 50 per cent of the ni- trogen can be utilized by crops the first year. Eno (1966), on the other hand, feels that 30 to 60 per cent of the nitrogen in poultry manure can be made available within 6 weeks of application to soil. Mar- tin (1972) generalized that 50 per cent of the nitrogen in steer, dairy, and poultry manures can become available to plants within 6 months of application. Pratt et al. (1973) estimated rates of annual release of nitrogen from organic manures when applied to irrigated lands and they expressed the availability of ni- trogen in terms of "decay series" (table 19). For example, with dry corral manure the decay series 0.40, 0.25, 0.06 means that the first year's release of mineralized nitrogen is 40 per cent of the amount ap- plied. In the second year, 25 per cent of the remaining organic nitrogen is released (15 per cent of the original organic nitro- gen) and during the third year 0.06 of the second year's residual organic nitrogen (2.7 per cent of the original nitrogen ap- plied) is mineralized. To achieve a con- stant release of nitrogen to growing crops each year, enough organic nitrogen must be added to supply sufficient mineralized nitrogen for the first year's crop needs (e.g. 250 pounds of organic nitrogen from dry corral manure will supply 100 pounds of mineralized nitrogen during the first year) . Decreasing amounts can be applied in following years, as is shown in table 19. If a constant rate of manure is applied each year (fig. 24) it is possible for the crop to be lacking in nitrogen for the first few years and yet to be provided with ex- cessive mineralized nitrogen in successive years. This decay series concept can be used to match crop needs with organic ni- trogen inputs and thus increase the effi- ciency of long-term manure use. Recoveries of manure nitrogen. Re covery of nutrients in manure by grow ing crops can be calculated from the aver age chemical composition and the weigh of the harvested material. Unlike avail ability estimates, recovery data accoun for variations in climate, species ability to 71 Table 19 TOTAL NITROGEN INPUT FROM VARIOUS TYPES OF MANURE REQUIRED TO MAINTAIN A YEARLY MINERALIZATION RATE OF 200 POUNDS PER ACRE DURING A 20-YEAR PERIOD- Number of years applied Manure type and decay seriest 1 2 3 4 5 10 15 20 nitrogen input, lb . per acre-year Chicken manure: 0.90.0.10,0.075,0.05,0.04.0.03 222 220 218 217 216 214 212 210 0.90,0.10,0.05 222 220 219 218 217 213 209 207 Fresh bovine waste, 3.5 per cent N 0.75, 0. 1 5, 0. 10, 0.075, 0.05, 0.04, 0.03 . . . 267 253 246 242 240 231 223 218 0.75,0.15,0.10,0.05 267 253 246 244 241 230 221 215 Dry corral manure, 2.5 per cent N 0.40,0.25,0.06,0.03 500 312 349 332 326 295 272 255 0.40,0.25,0.06 500 312 349 316 308 258 232 218 Dry corral manure, 1.5 per cent N 0.35,0.15,0.10,0.075,0.05,0.04 571 412 367 343 336 291 270 240 0.35,0.15,0.10,0.05 571 412 367 364 344 281 245 225 Dry corral manure, 1.0 per cent N 0.20.0.10,0.075,0.05,0.04,0.03 1000 600 490 475 451 361 300 261 0.20,0.10,0.05 1000 600 580 489 437 277 225 208 ♦From Pratt et al. (1973). tThe first of each pair of decay series presented is meant to represent a slower rate of mineralization of residual N, as would be the case for a colder climate. forage nutrients from the soil, and rates of application. Recoveries of nutrients applied with animal manures to growing crops vary with different manure treatment, soils, and cropping systems. However, it is reasonable to estimate that manure nitrogen is 25 to 50 per cent as recoverable by an initial crop as that supplied in chemical fertilizers, al- though residual effects may narrow this ratio in time. Herriott et al. (1963) measured the re- covery of nitrogen from slurry applications on some English grasslands; nitrogen re- covery in the herbage for four slurry ap- plications was 43.1 per cent, approximately 70 per cent of that recovered from mineral fertilizers. In a later experiment (Herriott et al., 1965) nitrogen recoveries on three different farms ranged from 34 to 89 per 'fill of that applied. The recovery was di- rectl) related to the cation- exchange capac- ity of the soil. Lipman and Blair (1918) applied 16 tons of manure per acre yearly to some soils for 20 years and average recovery of nitrogen for the period was 32.7 per cent, or 52.1 pel cent of thai recovered from sodium nitrate applications. Recovery variations ranged from I I .:") to 54.8 per DRY MANURE f ons/acre - yeor 24 10 15 TIME - yeo rs Fig. 24. Yearly release of manure nitrogen at various application rates of corral manure con- taining 25 per cent water and 1.5 per cent N on a dry-weight basis (from Pratt et al., 1973). cent during individual years. Table 20 presents results of a second 20-year experi- ment for comparison. Williams et al. (1963) compared nitro- gen recovery from farm manure and from mineral fertilizers by potatoes, kale, and permanent grass pasture (table 21). Po- 72 Table 20 APPARENT RECOVERY OF MANURE NITROGEN AND CHEMICAL NITROGEN FROM LIMED AND UNLIMED PLOTS* Per cent Per cent nitrogen Relative nitrogen Relative Plot treatmentt recovered per cent recovered per cent no lime limed Sixteen tons cow manure per acre-year . . 17.4 85.6 12.4 39.6 160 pounds NaN0 3 per acre-year . . . . 20.3 100.0 31.3 100.0 *Data of Lipman et al. (1928). tPlots were cropped in a 5-year rotation system; all received adequate phosphorus and potassium. Treatment continued for 20 years. Table 21 RELATIVE RECOVERIES OF NITROGEN FROM MANURE AND MINERAL FERTILIZERS BY POTATOES, KALE, AND PERMANENT GRASS PASTURE* Ratio of per cent nitrogen recovered Crop Nitrogen recovery (per cent of applied nitrogen) from manure to per cent nitrogen recovered from mineral fertilizers From mineral fertilizers: From manure Low rate of applied mineral nitrogen High rate of applied mineral nitrogen low rate of application high rate of application Potatoes .... 33 22 31 0.94 1.41 Kale 63 54 10 0.16 0.19 Grass 35 54 17 0.49 0.31 'Data of Williams et al. (1963). Table 22 ESTIMATED PER CENT NUTRIENT RECOVERY BY OATS AND FORAGE SORGHUM FROM DAIRY MANURE SLURRY* Application rate, (cm per week) Amount of element appearing in crop expressed as per cent of the element in applied manure Crop N P K Ca Mg Oats Forage sorghum . . . 0.63 1.25 2.50 2.50 5.00 153 92 55 105 63 118 70 42 105 63 153 92 55 105 63 38 23 13 41 25 25 15 8 21 13 'From Overman et al. (1971). tatoes were the most efficient utilizers of manure nitrogen, as they responded to the high potassium applied in the manure. Overman et al. (1971) examined differ- ences in nutrient recovery by oats and sorghum forage (Sorghum bicolor L. "Grazer S") from dairy manure slurry (table 22). The sorghum forage re- sponded better to heavier applications of manure nutrients than did the oats which were grown earlier in the spring. There is a dramatic decrease in the amount of 73 nitrogen recovered from heavier appli- cations of manure nutrients (table 22, fig. 25). The nutrient recovery and yield re- turn is greater from light applications of manure broadcast over a broader area than from the concentration of manures con- taining similar amounts of nutrients on a small area. Treating the manure before incorporat- ing it into the soil can have a marked effect on the subsequent recovery of nutrients by crops. In early experiments, Heck (1931) compared recovery of nitrogen from fresh, anaerobically-fermented, or dried cow ma- nure. Four crops of a standard rotation were grown in pots in which the equivalent of 12 tons of fresh manure per acre had been applied. The crops were harvested before maturity in each case. Recoveries of nitrogen for the four croppings are shown in table 23. Mineralization of the organic nitrogen during fermentation of the dung increased the nitrogen percentage recovered by the crops. Loss of large amounts of ammonia-nitrogen during dry- ing of the urine fraction of the complete manure resulted in lower nitrogen recov- eries. These data suggest that poor nitro- gen recovery by crops grown with corral scrapings and composts occurs because much of the soluble or mineralized nitro- gen can be leached, volatilized, or denitri- fied before the manure is applied to crop- land. Wet manure spread on the land and left to dry can also lose soluble ammonia- nitrogen. Nitrogen available in fresh ma- nure can be conserved by appropriate handling, as has been demonstrated re- cently by Hensler et al. (1971) (table 24). Recoveries of nitrogen by corn from ma- nure stored anaerobically were equal to, if not better than, those from fresh ma- nure. Drying treated dairy manure re- sulted in nitrogen losses of 2, 19, and 25 per cent for the aerobic liquid, fermented, and anaerobic liquid, respectively. All three treatments of the higher-nitrogen steer manure lost about 30 per cent of the nitrogen with drying. Availability and recovery of phos- phorus and potassium. Although phos- phorus and potassium do not undergo oxidative or reductive biological transfor- mations as does nitrogen, phosphorus is rapidly hydrolyzed and chemically precip- itated or adsorbed by other soil minerals. Potassium can be fixed in the lattice struc- ture of certain clays in some soils. These processes can limit the availability of phos- phorus and potassium applied in manures. Even so, some investigators have suggested that phosphorus and potassium in animal manures are at least as available as those supplied by mineral fertilizers (Salter and Schollenberger, 1939; Turk and Weide- mann, 1945; Kesler, 1966; Bartholomew, 1968). Sorghum forage 63 1.25 Cm DAI RY 2 50 5.00 SLURRY APPLI ED / WEEK Fig. 25. Recovery of nitrogen from a dairy manure slurry by oats and sorghum forage (data of Overman et al., 1971). TABLE 23 RECOVERY OF NITROGEN FROM COW DUNG AND COW MANURE (INCLUDING URINE) BY FOUR CROPS GROWN IN POTS* Per eent nitrogen Per cenl nitrogen recovered from dung and Manure treatment recovered from clung only urine combined Fresh 17 54 Fermented 40 42 fresh, dried 24 14 20 Fermented and dried 6 •Data Ol Hrrk ll'Mh. 74 table 24 EFFECT OF TREATMENT OF DAIRY CATTLE AND STEER MANURE ON CROP YIELD AND RECOVERY OF NITROGEN BY ONE CROP OF CORN GROWN IN POTS* Crop yield Recovery of N by crop Type and treatment of manuret (grams per pot) (per centi No manure 11 Dairy cow manure Fresh 20 44 Fermented 20 42 Anaerobic liquid 22 52 Aerobic liquid 17 18 Steer manure 32 Fresh 53 Fermented 32 54 Anaerobic liquid 33 66 Aerobic liquid 20 13 *From Hensler et al. ( 1971). fManure applied at rate equivalent to 15 tons per acre. Watkin (1957) has suggested that po- tassium excreted in urine is equal or supe- rior in performance to mineral potassium, but that dung potassium is somewhat in- ferior. Bertramson and Stevenson (1942) and Eno (1966) have suggested that avail- ability of phosphorus in manure is par- tially related to the rate of decomposition of organic phosphorus compounds. Brom- field (1961) estimated that inorganic phos- phorus in manures was available to plants and that organic phosphorus was not. The relatively high availabilities and recov- eries of phosphorus contained in animal manures is possible because all the ma- nure-phosphorus was recently in water- soluble form when absorbed by the plants serving as animal feed. MANURE AS A SOIL AMENDMENT Aside from the traditional values placed on animal manures as fertilizers supplying nitrogen, phosphorus, and potassium, sup- plementary traits that encourage plant growth have often been attributed to ma- nures. These accessory benefits have been ascribed variously to plant nutrients such as calcium, magnesium, or other micro- nutrients, or to physical changes in soil structure. Effects of manure amendments upon plant growth are complex and cannot be simplified by the use of any single catchall term such as "physical" (Bunting, 1963). Difficulties of separating out the individual physical and chemical effects contributed to soils by animal manures usually result in less than satisfactory identification of growth-promoting factors, either quantitatively or qualitatively. Con- cepts of manures as humus-building ma- terials which presumably maintain soil quality have frequently devolved upon de- batable and subjective observations. Chemical fertilizers have mostly re- placed the fertilizer demand formerly sup- plied by animal manures, but the extensive use of chemicals ". . . is increasing their [manures'] values as soil conditioners'" (Taiganides, 1970). Viets (1971) states that ". . . older farming areas understand the corollary values of manures and regu- larly utilize animal wastes." Repeated substantial additions of animal manures increase the organic matter con- tent of the soil. Benefits of a large and stable humus supply in the soil are additive to temporary benefits resulting from a single application of manure. In Califor- nia's warm climate even large additions of manures can decompose rapidly, but any residual organic matter derived from manures will help maintain or even in- crease soil reserves of organic matter and nutrients. Supplementary nutritional values Because animal feeds are derived from plants, an entire complement of essential plant nutrients is contained in animal ma- 75 nures. Although plant micronutrients are normally supplied by soils, soil deficiencies can be corrected by manure applications. For example, manure has been found to be an excellent source of zinc (Barnette and Warner, 1935; Grunes et al., 1961; Miller et al, 1969), iron (Miller et al, 1969), and manganese (Skinner and Ru- precht, 1930) for soils and plants deficient in these elements. Marginal micronutrient deficiencies evident only after repeated cropping with refined nitrogen, phos- phorus, and potassium fertilizers can be prevented with supplementary applica- tions of manure. Importation of feeds from various parts of a countryside is common among animal growers, while manure from animals grown on these feeds is generally distributed only within the vicinity of the animal-produc- tion facility. This flow of nutrients could be used advantageously to correct or guard against micronutrient deficiencies. For ex- ample, the large numbers of animals (par- ticularly horses) kept in cities prior to the 1920's created manure disposal problems. The City of London in the days of horse- drawn drays and carriages, required any supplier of farm products to the city to also remove a load of manure. In recent, years, researchers noted that the frequency of micronutrient element deficiencies in farmlands near London became more prominent circa the 1940's, at which time stable manures were no longer an export item of the city (E. J. Hewitt, private com- munication, 1956) . Nutrient retention, solubility, and avail- ability can be influenced by manure appli- cations. Nutrients bonded to the organic- fractions of animal manure and residual humus that possess cation and anion-ex- change properties resist leachng but are still available for plant uptake. These re- tentive properties of organic manures are of more obvious value in soils of low clay content and low natural ion-exchange rapacity. Organic acids and carbon dioxide pro- duced by soil microorganisms during ma- nure decomposition may solubilize certain nutrients from the mineral phase of soils and increase their availability to plants. Miller et al. 11069) speculated that the organic fraction of manure caused solubil- ization of zinc and iron. Tan et al. (1971) noted that sonic organic molecules, spe- cifically polysaccharides, cornplcxed micro- nutrient cations such as copper, zinc, and manganese and held them in forms highly available to plants. Anaerobic microenvi- ronments of the soil induced by decompos- ing manure convert insoluble oxidized forms of iron and manganese to more soluble reduced forms which are more readily available to plants. Manures can supply these types of sup- plemental nutritional benefits to soils and plants when used as supplements to macro- nutrients supplied from chemical or organic fertilizers. Effect of manure on soil's physical properties Much evidence suggests that manures can effect beneficial changes in soil phys- ical properties by enhancing aggregate crumb structure in soils. Although crop yields are seldom limited by poor aggre- gation in the better agricultural soils, workability and oxygen diffusion in clay soils are promoted by increased aggrega- tion, and friability, root penetration, and water-holding capacities can be improved in compactable fine sandy soils. Soil amendments that can improve physical conditions of difficult soils, or maintain desirable physical conditions of soils that otherwise might deteriorate under inten- sive cultivation, are not always demon- strably beneficial in one or two growing seasons. Nevertheless, there remains little question that continuing use of manures results in noticeable advantages in improv- ing or maintaining desirable soil physical structure and other soil properties that encourage plant growth. Physical properties of soil are basically the result of soil texture, quantity and qual- ity of salts in the soil, cultivation, and climatic and vegetative influences. The proportions of salts and total salt content of manures vary widely as they do in soils themselves. Manures having high propor- tions of monovalent cations (such as so- dium and potassium) to divalent cations (such as calcium and magnesium) have potentials for salt-induced deterioration of soil structure. With proper water manage- ment, however, beneficial effects of manure organic matter on the physical properties of soils more commonly outweigh deleteri- ous salt effects, with resultant improvement in the soil structure. Soils having good initial physical char- acteristics, either with large or small 76 Table 25 EFFECT OF SWEET CLOVER AND STABLE MANURE (ADDED EVERY 2 YEARS) ON AMOUNT AND SIZE OF WATER-STABLE AGGREGATES* Aggregate size (mm) Check (no treatment) Sweet clover plus manure >4 4 to 2 per rent of s 9.2 7.6 9.3 12.4 23.7 4.1 65.3 37.5 ill by weight 20.8 12.0 2 to 1 11.8 1 to 0.5 15.8 0.5 to 0.25 17.5 0.25 to 0.10 2.5 Total > 0.10 80.4 Total > 0.5 60.4 'From Guttay et al. ( 1956). Samples were collected from 6 to 12 mm dry-a««re«ate fractions. amounts of organic matter initially, have been known to sustain good crop produc- tion for several decades without benefit of added organic matter. However, animal manures have benefited soils with initially poor soil structure and soils whose physi- cal structure had deteriorated with culti- vation. Swanson (1954) noted that physi- cal qualities of many Connecticut soils were deteriorating with cultivation, and that manured fields yielded 25 to 40 per cent more crop than fields in poor physical condition that were fertilized with equiva- lent nutrients from chemicals alone. Bunt- ing (1963) noted increased crop response attributable to improved soil physical con- ditions on nine of fifty-six manured sites in England. Aggregation. The proportions and dis- tributions of sand, silt, and clay in soil ag- gregates control the soil's pore space, bulk density, strength, water infiltration, shrinkage, and resistance to compaction. Organic manure and manure decomposi- tion processes effect redistributions of soil particles into aggregates, and thus influ- ence physical characteristics of soils. Soils containing organic residuals from long- term manure applications gradually ac- quire more of the qualities of organic soils which are generally conceded to have de- sirable physical properties. Laboratory examination of changes in- duced in physical properties of soils amended with animal manures have con- firmed farmers' observations of increased aggregation and friability. Guttay et al. (1956) compared the granulation of con- trol soils and those amended periodically with stable manure and sweet clover for almost 20 years. After that period, per cent of aggregates greater than 0.5 millimeters were 37.5 per cent in the control and 60.4 per cent in the treated soils (table 25). Residual effects on granulation lasted only about 1 year. Experiments in our labora- tory (Hafez, 1974) showed increased ag- gregation of soil particles into granules greater than 0.25 millimeters in a clay soil when amended with various types of an- imal manures and incubated for 3 weeks. Aggregation of smaller-sized soil frac- tions into larger particles tends to reduce close packing and provides a higher pro- portion of large pores in the soil; this permits more rapid transfers of oxygen and water into the root zone. Absence of large pores can also restrict root penetra- tion into available soil volumes so that plant nutrients and water uptake are im- paired. Aldrich et al. (1945) and Wil- liams and Cooke (1961) noted increases in pore space of soils that had been amended by use of animal manure for several years. In other experiments (Wil- liams and Cooke, 1961) manure did not improve stability of aggregates and pore spaces in irrigated sandy soils but did improve aggregate stability in clay soils (table 26). Apparently, the stabilitv of sandy soils depends more upon fine roots which can physically bind individual sand particles into aggregates. Quastel and Webley (1947) noted an immediate increase in the aeration of a wet soil amended with strawy farmyard manure. The beneficial effects of the ma- nure were attributed both to the physical effects of the straw in the manure and to the chemical properties of manure which 77 Table 26 EFFECT OF SOIL TREATMENT ON STABILITY OF SOIL AGGREGATES AND ON SOIL PERMEABILITY AFTER SLAKING* Soil type and number History and treatment Instability factort Permeability! Clay soils 1 Fallow Fallow plus manure Grass Plowed grassland Cereals Cereals plus manure Grass Forest nursery Arable per cent 15 5 42 46 51 43 7 51 ml per hr-cm 2 20 2_ 3 4 Sandy soils 5 6 7 8 130 520 360 30 50 2,600 20 9 10 11 80 220 40 *From Williams and Cooke (1961). Aggregates were 4 to 6 mm in diameter. + Loss in pore space after slaking. JTo water after slaking. affect soil aggregation, but the benefits due to straw were emphasized. Permeability of soils. Soil permea- bility appears to be directly enhanced by undigested fibrous particles in fresh ma- nures, as well as by the much smaller particles that tend to increase pore-space indirectly through aggregation, although Williams and Cooke (1961) observed that benefits to permeability of a sandy soil from additions of farmyard manure were probably due to pores formed from coarse manure particles rather than from aggre- gation. Both increased and impaired soil per- meability conditions were reproduced in small soil-columns in our laboratory with single admixtures of 5 per cent animal manure with soils, which were then sub- jected to tests for hydraulic conductivity. These experiments clearly demonstrated that the large fibrous particles present in manure were mainly responsible for pro- nounced increases in the hydraulic con- ductivity of a manure-treated sandy loam soil (table 27). Chicken manure, with its relatively small proportion of fibrous par- ticles, actually decreased hydraulic con- ductivity of untreated soil. However, when fibrous particles were extracted from cattle manure and mixed with chicken manure. the conductivity of the soil amended with this mixture was greater than that of chicken manure alone. The soil column treated with manure fibers had a higher hydraulic conductivity than did the con- trol soil. The initial effect of manure on soil permeability may thus depend on the pro- portion of large fibers in manure, while re- sidual effects from long-term treatment that results in improved permeability may be the result of improved soil aggregation. The amounts of organic matter com- monly added to soils with field appli- cations of manure usually do not yield readily observable changes in water in- filtration rates where other cultural prac- tices dominantly affect soil's physical prop- erties. Although Zwerman et al. (1970) noted increases in water infiltration in soil under continuous corn plantings when 6 tons of manure per acre were incor- porated each year, similar effects of ma- nure were not evident in rotation plant- ings. Zwerman et al. (1970) also stated that when organic matter from normal crop residues or green manure crops is added to soil the physical effects of manure may be obscured. Water infiltration rates decreased on plots that had been fertilized solely with chemical fertilizers in these latter experiments. Aldrich et al. (1945) noted that although orchard plots treated with animal manure were highly perme- "Thc term "permeability" of porous media such as soils is often used as synonym for "hydraulic conductivity," although in a strict sense permeability means a soil-flow property which is dependent on fluid passing through soil. 78 table 27 EFFECT OF MANURE FIBERS ON SATURATED HYDRAULIC CONDUCTIVITY OF DINUBA FINE SANDY SOIL* Treatment Hydraulic conductivity— K No manure added cm per hr 10.30 ' 1.00 Five per cent chicken manure 2.30 • 0.09 Five per cent cattle manure 5.31 • 0.69 Five per cent chicken manure adjusted to the fibrous level ( 1 mm) of cattle manured 4.69 • 0.49 Five per cent fibers from dairy cattle manuref 12.32 • 1.57 ♦From Hafez et al. (1974). tFibers obtained from dairy cattle manure. able to water, nitrogen fertilizer applied as a calcium salt (e.g., Ca (N0 3 ) 2 ) im- proved water infiltration more than did farmyard manure due to effects of the calcium on soil aggregation. Excessive amounts of soil-adsorbed monovalent cations (e.g., Na, K) gener- ally result in dispersive effects detrimental to soil structure and consequently in low- ered permeability. Experiments in our lab- oratory (Hafez, 1974) have shown, how- ever, that cattle manure could offset de- leterious effects of adsorbed sodium on soil hydraulic conductivity. This was demon- strated with a fine sandy loam soil artif- icially converted from a normal low-sodium soil to a sodic-soil having 50 per cent of its exchange complex occupied by sodium ions. Five per cent cattle manure added to this highly-dispersed sodic soil in- creased its hydraulic conductivity to levels comparable to the conductivity of the original soil with no manure added ( fig. 26). Seemingly contrary to information al- ready presented here, which says that an- imal manures can increase soil permeabil- ity, manure holding ponds apparently rapidly form seals that restrict water in- filtration below the ponds. Although phys- ical, chemical, and biological processes contribute to the formation of a bottom seal, biological processes appear to be the most significant (Davis et al., 1973). Fine particles in manure settle in the pond and clog soil pores, and an accumulation of biological slime and sludge completes the barrier. There is some evidence that the fiber in manure increases the rate of seal- ing (Meyer, 1973), but ponds also sealed when filled with manures from which the fibrous portion had been removed (Davis etal, 1973). Soil compaction. Soil compaction (from pressures created by field ma- chinery) breaks down soil aggregates and reduces soil pore space and permeability. Animal manures have successfully in- creased soil resistance to experimental compaction (Hafez, 1974). Williams and Cooke (1961) have shown that arable soils amended with animal manures, and then mechanically compacted, had greater per- meabilities to water than did similar soils not treated with manure. Soil crusting. Soils with low aggregate stabilities tend to condense into tough and solid masses when dried. Such soils often form surface crusts, which may delay or even prevent seedling emergence or injure seedlings as they force openings through the crusts (Timm et al., 1971). Small- seeded plants are more sensitive to soil crusting. Gowans et al. (1965) showed that animal-manure incorporation doubled the germination and emergence of tiny lettuce seeds through a typical soil crust, and that some natural and synthetic soil- conditioners ameliorated deleterious soil- crusting conditions even more. Nuttall (1970) and Hafez (1974) found that ma- nure reduced the forces necessary to break soil crusts, as shown by laboratory mea- surements of the soils modulus of rupture. These experimental values were correlated with seed emergence through prepared crusts. Exceptional shrinkage and cracking of soils with high montmorillonitic clav con- tents can damage plant roots as well as complicate tillage and preparations of seed-beds. Manured soils seem to shrink less and the shrinkage was slightly less dependent on initial soil-water content ( Hafez, 1974) . 79 0.001 12 3 4 5 PER CENT MANURE Fig. 26. Effect of cattle manure on hydraulic conductivity of Dinuba fine sandy loam soil ad- justed to various exchangeable-sodium percent- ages. Original soil contained 2 per cent ex- changeable sodium (from Hafez, 1974). Water-holding capacities of soils amended with animal manures. Only part of total soil moisture is held in the root zone with sufficient tension to pre- vent free drainage and still allow re- moval by actively transpiring plants at rates sufficient to maintain plant-turgor. For comparison purposes, the "available water capacity" of a soil is usually defined as the amount of water held at a tension of one-third atmosphere (field capacity) less the amount of water held at 15 atmospheres (permanent-wilting-percent- age). Field capacity is sometimes ex- pressed as the amount of water held in a field soil after irrigation water has drained through. Salter and Haworth (1961) correlated field measurements of field capacity of manured soils with a labora- tor) tension of 0.05 atmospheres instead of witli one-third atmosphere tension. (The terms "field-capacity* and "permanent- Mrilting-percentage" are approximate. though practical. Flow of water through soils is dynamic and rarely reaches a steady state, bui (low rates can become SO low that a "capacity" may be implied.) Animal manures have water-holding capacities per unit weight of material several times greater than the correspond- ing water-holding capacity of a mineral soil. Therefore, it would be expected that a newly-formed soil-manure mixture should have an initial water capacity pro- portional to the weighted average of the water-holding capacities of the soil and manure fractions taken separately (Ja- mison, 1953). Laboratory experiments (Hafez, 1974) have shown that the one- third atmosphere water-holding capacities of admixtures of manure with both sandy and clay soils could be fairly well pre- dicted from the sum of the water-holding capacities of the soil portions and the ad- mixed manure portions. However, vari- abilities of the experimental values oc- curred which could not be explained by ex- perimental error. Thus in addition to the well-known dilution effect produced by mixing one material with another of a tremendously different water-holding ca- pacity, there are other and still undefined reactions between manurial constituents and soils that influence the water-holding properties of the mixtures. Salter and Haworth (1961) and Salter and Williams (1963) showed that after 9 years of incorporation of farmyard ma- nure at rates of 20 tons per acre for each crop, available water held in an easily compacted sandy soil was increased more than could be explained by the accumula- tion of organic material of a higher water- holding capacity. The additional water in- crements were held at lower tensions and were thus available for crop use (fig. 27) . Although additional available water held in the heavily manured soil amounted to only that used by crops during IV2 to 4 English summer days, this additional water-holding capacity could be beneficial in carrying plants through times when larger gaps between rain showers occurred. For example, Holliday el al. (1965) were able to correlate crop responses on manured soils with the maximum soil- moisture deficit in dry years, whereas the response in wet years was only in propor- tion to the nutrients applied in the manure. Since water-holding capacities of soils are reduced by compaction, manured soils should hold more available water by re- sisting mechanical compaction (Hunting, L965). An additional water-related benefit of manured soils could be increased infil- 80 - 0. LU cc I o. % 0. o 6 0.8 1.0 12 14 16 0.2 04 06 4 6 8 10 VOLUME OF AVAILABLE WATER RETAINED (in) Fig. 27. Effect of farmyard manure (FYM) on volume of water retained in the top 6 inches of soil at differential soil-moisture tensions (from Salter and Williams, 1963). tration rates that would allow greater per- centages of applied water to penetrate into the root zone (Jamison, 1953). Biological benefits to soils from manure amendments Only limited explorations have been made of effects of manures upon soil biological population characteristics and interac- tions, and upon biologically-produced sub- stances affecting crop growth. Salter and Schollenberger (1939), mention early speculations that growth-promoting auxins and creatinine had been associated with manured soils and concurrent increases in crop production. Changes in microfloral characteristics and enhancements of car- bon dioxide production in manured soils were also implicated in crop-response benefits. Mankau (1968) noticed a reduction of root-knot nematode disease during a 4-year period in crops grown on soils amended with animal manure or alfalfa green-manure. His organically fertilized plots showed increased microbial and total nematode populations concurrent with better water penetration and improved soil tilth. Chiang (1970) reported that mite pre- dation of corn rootworm increased from 19.7 per cent to 63 per cent with additions of 50 tons of manure per acre, with an over-all benefit in crop vigor and yield from the rootworm reductions. There is some evidence that animal manure or other organic matter in soils can aid soil microorganisms in a more rapid degradation of DDT (Anon., 1970) and other chlorinated hydrocarbon pesti- cides (Wang, 1972). These effects were apparently more predominant in anaero- bic soils. Improved rates of removal of persistent pesticides from soils may thus become another recognized value of add- ing manure to soils as an amendment. Values of manure in land and water conservation Improvements in soil aggregation, crop- cover, and water penetration resulting from using animal manures as combina- tion soil amendments and fertilizers will contribute toward reducing surface run- off and erosion. Neal (1939) found that manure applied at the rate of 8 or 16 tons per acre reduced runoff and erosion on both fallow and corn-cropped plots. Relative erosion control benefits from ma- nure additions were greater on plots planted to corn, although runoff reduc- tion was also considerable on fallow plots. Runoff water from manured plots mon- itored by Hensler et al. (1969) averaged 76 to 84 per cent of that from check plots. Similarly, Minshall et al. (1970) were able to reduce summer rainfall runoff by almost one-half by incorporating manure with soils. Winter runoff from snowmelt was unaffected by the manure treatment. 81 Manure can be routinely broadcast as an in the stabilization of cut-banks and other erosion-control measure for sloping land land scars, as well as a routine aid in min- where corn is grown (Minshall et al., imizing runoff and erosion losses from 1970), and could be used as an early step sloping agricultural lands. ALTERNATIVE USES OF MANURES Manure as feed for animals The organic constituents of fresh plant materials are only partially digested by herbivorous animals, as may be readily shown by comparing chemical analyses of fecal wastes with analyses of the orig- inal rations. The most casual observations of population buildups of flies, beetles, and other insects attracted to fecal materials clearly demonstrate that some types of organisms thrive on remaining food values of fecal materials. Digestibility and avail- ability of energy foods from rations range from high for sugars, starch and other simple organic compounds, to essentially nil for lignins. Therefore, the amounts of undigested materials of excrement depend largely upon the proportions of rapidly and slowly digestible components of any particular animal feed. The considerable amount of nutritive feed material that escapes digestion in the alimentary tracts of domestic animals is combined with new materials synthe- sized in the gut, and some of the remain- ing food value is recoverable if recycled as supplementary feed for farm animals. Feeding of animal wastes takes advantage of the fact that more of the slowly-digest- ible fractions in animal feeds could be utilized if residence times in the digestive lumen or the lumen itself were longer so that foods would be subjected to more prolonged digestive attack. The amount of ration material that escapes digestion and yet becomes available upon "refeeding" is related to initial particle sizes of the ra- tion, the chemical composition of the di- etary mix, and the nature of the digestive processes which, in turn, influence the rate of passage through the digestive tract. Because of these differences. Smith ( 1971 ) estimates that 5 to 70 per cent of ruminant fecal cellulose will be digestible tin* second time through the animal. Digestible fecal cellulose, hemi-cellulose, dry matter and nitrogen can be increased by treatments with strong oxidants and chemical bases (Smith et a/., 1969). Some of the microbiological proteins, amino acids, and vitamins, such as B 12 , synthesized in the rumen of ruminant animals and lower digestive tracts of most herbivores are not always formed at sites from which they can be absorbed, and are thus passed on as waste. However, some of these can be made available by refeeding. McElroy and Goss (1940a, b) noted the synthesis of vitamins K, B 6 , and riboflavin in the rumen of cows and sheep. Synthesized riboflavin excreted in cow manure was of benefit to chicks on a diet deficient in that vitamin in experi- ments conducted by Hammond (1942). Bohstedt et al. (1943) observed that the benefit of cattle manure consumed by hogs following steers could be in the vitamin B G content as well as in undigested corn fragments. Much of the benefit from "un- identified growth factors" in ruminant manure fed to poultry and swine has been attributed to the synthesized vitamins con- tained in the manure. Inorganic nitrogen found in manures can be utilized by rumen microflora in cell-protein synthesis. Ruminant animals benefit from microbial protein synthesized from non-protein nitrogen. Nitrogen-rich manure, including the mineralized nitro- gen fractions can be a good nitrogenous supplement for ruminant animals. Poultry, however, can utilize only true protein and therefore much of the non-protein nitro- gen in feces fed to poultry is excreted in their manure. Wehunt et al. (1960) found that chicks fed a ration containing some poultry manure gained weight only in proportion to the true protein content of the diet. Cattle manure has been fed in various dietary proportions to poultry (Palafox and Rosenberg, 1951), cattle (Anthony and Nix, 1962), swine (Bohstedt et al., 1943), and sheep (Anthony, 1966). Dur- ham et al. (1966) formulated rations that included cattle manure for pullets, hens, cattle, sheep, swine, and catfish. Anthony (1967, 1968, 1969) has ensiled fresh manure and hay and has obtained excel- 82 lent results feeding this "wastelage" to steers, breeding cows, and ewes. Only vitamin A was found to be deficient in the wastelage rations, which contained up to 57 per cent manure. In general, 10 to 15 per cent cattle manure can be included in animal rations, with no apparent deleterious effect on the quality of the ration. Ration digestibility is usually inversely proportional to the amount of manure included in the diet, with a consequent slight drop in animal production at the higher levels of manure in the ration. Palatability may also pose a problem at the higher levels. Poultry manure has been included in the rations for chicks, hens, cattle, and sheep. Studies of production of laying hens fed diets including from 10 to 40 per cent dried poultry manure showed that there were no significant effects on the number or weight of eggs produced (Fle- gal and Zindel, 1969; Hodgetts, 1971), the quality of the egg shells (York et al., 1970), or the taste of the eggs (Flegal et al., 1970). Weight gains of pullets were unaffected by up to 20 per cent dried poultry waste in the ration (Flegal and Zindel, 1970), but the ration did not sup- ply sufficient energy for rapid gains of broiler chicks. A commercial preparation of dried poul- try waste is currently marketed with con- siderable success in Britain. The average dry matter digestibility of this feed is 56.6 per cent, and the energy digestibility is 60.3 per cent (Lowman, 1969). In one experiment this product composed up to 100 per cent of the ration for sheep. Experimentation with poultry manure as a source of feed for ruminant animals has at least a 30-year history in the south- ern U. S. The supply of available manure is great in these areas, and it has often been included as a low-cost supplement for ruminants. Twenty-five per cent poul- try manure in the ration of growing steers did not affect the taste of the resultant meat (Rhodes. 1971), as shown by a de- manding taste test. Poultry litter with various base materi- als has been included in rations fed both to cattle (Drake et al., 1965; Fontenot et al., 1971) and sheep (Bhattacharya and Fontenot, 1966; Fontenot et al., 1966; Noland et al., 1955). In general, litter with a woody base is less nutritious than those formed on other bases (e.g., peanut hulls). Cattle grown on rations that in- cluded 25 per cent peanut hull litter had growth rates, feed efficiencies, and flavor similar to those of cattle grown on con- ventional feed (Drake et al., 1965). When sheep were fed rations containing 25 and 50 per cent peanut hull and wood-shaving litter, Bhattacharya and Fontenot (1966) found an average apparent digestibility of 72.5 per cent. Energy, dry matter, and nitrogen-free extract (NFE) digestibil- ities were lower for the 50 per cent litter ration than for the 25 per cent ration. In other experiments (Bhattacharya and Fon- tenot, 1965; Fontenot et al., 1966), nitro- gen retention and over-all ration efficiency for sheep were lower when litter was 100 per cent of the ration. Obviously, there is a limit to how much recycling can be accomplished before the accumulated ash constituents ( salts of cal- cium, magnesium, phosphorus, etc.) be- come too high and the organic fraction too low for excreted materials to be con- sidered useful as feeds. One manure- cycling suggestion calls for supplementa- tion of range cattle with manure from feedlot operations — the range cattle would utilize available nutrients and then distrib- ute the remainder throughout grazing areas via their droppings. In one experi- ment (Hull et al., 1973), animal manure from feedlot cattle was pelletized with barley (25 to 75 per cent barley) and some molasses to enhance palatability. These materials were then fed to range cattle during periods when supplementary rations could be beneficial. Palatability of the manure supplement was no problem after the cattle were exposed to the pellets. Cattle weight gains testified to beneficial effects of the supplements, although the barley in the pellets probably induced the majority of the gains. Some recently-proposed schemes to re- use animal wastes involve an indirect conversion of feed from manures. Calvert et al. (1969) and Calvert et al. (1971) have grown the common housefly (Musca domestica) in poultry manure and ground the pupae and adults for use as poultry feed. The protein content of ground pupae and adult flies was greater than that of soybean meal and the amino acid and fatty acid composition was ". . . reasonably well balanced . . ." for use in animal feeds. Holmes et al. (1971) harvested protein- aceous residue from a swine manure oxi- 83 dation ditch and analysis of the centrifuged residue, minus larger particles, showed the content of protein and some essential amino acids to be greater than that of corn. Oswald (1971) proposed a system of harvesting algae from aerobic manure treatment ponds — algae has been used with some success as feed for animals. The success of these three proposals, and of similar ones developed in the future, will depend upon changing economics that may warrant the expense of the additional treatment. The possible hazard from residual hor- mones, feed additives, heavy metals, and pathogens present along with beneficial nutrients in manures has been a much- discussed deterrent to use of animal ma- nures as feeds. Hammond (1942) noted that an androgenic hormone present in some cow manure being used for feeding chicks benefited male chicks but was detri- mental to female chicks. A hormone con- tained in dried poultry wastes being fed to cows was implicated in abortions (Griel et ai, 1969) . Morrison (1969) found from 15 to 30 parts per million arsenic in poul- try waste from chickens being fed organic arsenical compounds, but Brugman et al. (1968) as a result of experiments on feed- ing poultry manure to lambs, questioned whether the arsenic fed to lambs via this route did any harm — detailed analyses could not detect the presence of arsenic in selected organs of these lambs. Alexander et al. (1968) ascertained the presence of some potentially harmful bac- teria in various samples of poultry litter being used for refeeding in Canada. Car- riere et al. (1968) suggest that some my- cobacteria in poultry-litter, even though not pathogenic, could give a false tuber- culin test result when the litter was fed to cattle and thus could complicate con- trol of the disease. Increased exposure of animals to pathogenic organisms in ma- nure used as feed suggests possibilities of increased chances for transmitting disease (pages 56-62). However, reports of dis- ease transmission via this route are rare, if not absent, in the literature. Calvert (1971) and Frobish (1971) reviewed the cycling of residual feed addi- tives in jK)ultry and swine feces and found no definite information about the break- down and rate of exeretion of antibiotics, hormones, and analajrous compounds cur- rently being fed commercially to animals. There is also little information on any effects these waste residuals might have upon the well-being of animals receiving manures as a portion of their diet. Defin- itive research information on the break- down, transformation, excretion, and sub- sequent effect of these feed additives, would be of benefit to growers who might contemplate refeeding manures. Such knowledge could determine what treat- ment of manures used in feeding would help guard against the potential hazards mentioned above. Interest in manure feeding has been generated mostly by economics, for an- imal wastes are known sources of cheap and readily available protein, energy, and perhaps other re-usable nutrients. Most experiments with such feeding have been directed toward gaining assurances that manurial wastes will not be harmful as feed additives rather than toward learn- ing about any special benefit to recipient animals. If current trends that make ma- nure a liability to the animal feeder con- tinue, more of these wastes will be re- cycled as animal feeds. Public opinion and governmental regulation may be slow in acknowledging the desirability of the trend toward re-utilization of a waste, but with appropriate conditions for handling and sanitation the chances are that ma- nure feeding will become much more common than it is now. Manure as a source of fuel energy Current U. S. trends toward serious fuel- conservation efforts indicate that some of the chemical energy bound in animal ma- nures will in the future be utilized for its fuel value, particularly in areas where large stable supplies of animal manures are within easy reach of market outlets for fuel. Methane, or common "town gas," can be generated by microorganisms during natural decomposition of organic wastes under anaerobic conditions (pages 26- 28), and usable mixtures of methane, hy- drogen, and other gases can be drawn from manure slurries digesting in closed con- tainers. The sludges remaining after such anaerobic digestion contain much of the nutrients originally present in manures and can be used for fertilizer or combusti- ble fuels. Some experimenters arc 1 now in- vestigating nutritive values of these sludges 84 (Anon., 1972). From 60 to at least 125 cubic feet of impure methane gas can be produced from 100 pounds of fresh ma- nure, and this gas has a heating value of about 600 BTU per cubic foot (table 28). Methane-producing plants were quite common in Europe during World War II as a result of the fuel shortage, but there has been a steady decline in their numbers since that time ( Allred, 1966) . Fairbank (1973, personal communication) reported near-total abandonment of manure diges- ters for methane recovery in central Europe for economic reasons. The high initial cost of the digesters and the supervision they require has probably discouraged their development, but current interest in me- thane production from organic wastes may result in the building of simple and inex- pensive plants such as those used in India in recent years. Controlled burning of air-dry manure in a suction-gas producer in the presence of water will yield a combustible mixture of carbon monoxide and hydrogen with a heat value of 80 to 85 per cent that of methane (H. F. Amundsen, personal com- munication, 1971). The process has been used for years in Asia as a source of power, and Amundsen has suggested a program for using this process to relieve the ma- nure build-up problem in the Chino- Corona dairy area of southern California. Economic competitiveness of the gas pro- duced will depend on the cost of trans- porting, drying, and structuring (e.g., pelleting, cubing) the manure as compared to the cost of other available fuels. Two separate energy-yielding processes, pyrolysis and hydrogenation, have been suggested by the Bureau of Mines (Anon., 1972) . During pyrolysis, manure is heated at 900°C for 6 hours at normal atmos- pheric pressures and converted to gas, oil, and solids. Each of the three products can be used for fuel; the gas has a heat value of 500 BTU per cubic foot, the oil pro- duces 15,000 BTU per pound, and the solid residues give 5,000 to 13,000 BTU per pound. Hydrogenation of manure at ele- vated pressures of 2000 to 5000 pounds per square inch in the presence of carbon mon- oxide and steam at 380°C for 20 minutes, produces a low-sulfur paraffinic oil with a heat value of 14,000 to 16,000 BTU per pound. Two barrels of this oil can be pro- duced from a ton of dry organic waste: the energy-equivalent of three-quarters of a barrel would be used in the process (An- derson, 1972). In a recent publication, Anderson (1972) suggests that organic wastes might be converted to fuels in order to reduce fuel imports as well as to relieve some of the solid waste burden of this country. According to figures presented in Ander- son's 1972 report, animal manure makes up 19.1 per cent of the available organic solids presenting a disposal problem. In 1971, the oil potential from all available organic solids would have amounted to only 3.0 per cent of this country's crude- oil demand. Substantial amounts of energy are avail- able from the combustion of manures (table 29). "Synthesis gas," a gas with 2 volumes of hydrogen and 1 volume of car- bon monoxide per 1 volume of nitrogen, can be produced by partial combustion of manure (Herzog et at., 1973). Subsequent reaction of the synthesis gas with steam generates a gas with 3 volumes of hydro- gen to one of nitrogen. The nitrogen and hydrogen mixture is then passed over a Table 28 METHANE PRODUCED DURING ANAEROBIC DECOMPOSITION OF ANIMAL MANURES* Total gas production Methane Heat value Type of manure Cubic feet per animal-day Cubic feet per Cubic feet per pound of 100 pounds of volatile solidst fresh manure Per cent of total gas produced BTU per animal-day Swine Dairy Poultry ...... 6.3 42.0 0.4 8.9 125.0 5.2 59.4 5.3 99.2 55-75 60-80 60-80 3600 25000 250 *From Taiganides et al. (1963). tThe organic faction of manures. 85 catalytic converter and combines stoichio- metrically to form ammonia (NH 3 ) gas. Almost all manufactured ammonia is formed from synthesis gas, with natural gas supplying the energy rather than the animal manures that would be used in this case. Halligan and Sweazy (1972) have also theorized that production of a synthesis gas for manufacturing am- monia would be a preferred alternative to conversion of manure to gaseous or liquid fuels. Nitrogen fertilizers are often intimately associated geographically with crop and animal production, and 700 pounds or more of ammonia can be pro- duced from a ton of manure solids. Resid- ual manure solids, consisting mostly of po- tassium, calcium, and phosphate salts, may be recoverable for use as fertilizers. Of all the energy-from-manure schemes, the relatively simple conversion of ma- nures to synthesis gas and ammonia would appear to have the least problems of stor- age and marketing. Successful processing of manures to capture their energy content depends on the use of dry manures, a dis- tinct advantage for producers in warm, dry climates such as are found in central and southern California. Miscellaneous uses for manure Animal manures, litters, and manure com- posts have been used as bedding or litter. In one system (Senn, 1971) manure from a dairy is composted rapidly with the aid of forced air, and a portion of the compost is used as bedding in a loose-housing sys- tem; dry compost is used in winter to re- duce sloppiness in the covered corrals, and spare compost is marketed as a soil amend- ment. Bramhall (1970) suggests that fi- brous manure solids ejected from manure separators can also be reused as absorbent bedding. At least one dairy in central Cali- fornia is successfully recycling separated solids for use as bedding in free-stalls. Broiler litter has been composted and re- covered for further use as litter. Chaloupka et al. (1968) report good performance of broilers on recovered litter and fewer con- demnations due to Marek's disease (leuco- sis) in these birds than in birds grown on fresh litter. A novel approach to animal manure util- ization by one researcher has led to the de- velopment of a variable-density, board-like building material manufactured from com- binations of ground-glass and manure (Anon., 1971). Although the patented Table 29 HEAT VALUE OF ANIMAL MANURES (MOISTURE-FREE BASIS)* Type of manure BTU per poundt Ash content (per cent) Chicken . . 6289 29.3 6207 29.3 4968 36.1 5824 35.9 Dairy . . . 7520 36.0 7434 17.0 4494 49.9 8082 14.2 8017 18.0 Beef. . . . 6821 27.4 6639 34.5 4079 51.9 8431 11.3 6156 32.3 Turkey . . 5790 5817 44.0 43.6 Horse . . . 6984 7308 24.6 Swine . . . 27.7 Sheep . . . 7666 26.3 *\ mm Siegcl el nl (unpublished data). M <>r comparison purposes. coal h;is ;i BTU per pound ruling of HI 00 to 15000; oak wood has a heal value of 8320 B I I per pound 86 process incorporates only 5 per cent ma- nure in the final material, there are hopes for increasing this percentage. Using a re- lated process, manure can also be processed to yield a black pigment similar to that currently used in automobile tires. Disposal of manure Although manure is a natural resource that deserves to be conserved and not wasted, economic realities in this country are such that it is sometimes "cheaper" for the ani- mal grower to dispose of manure rather than put it to use (Clawson, 19706). Var- ious systems proposed for disposal include permanent lagooning, land-fill, land appli- cations, ocean discharge, and incineration. Although economics usually dictate the actions that producers can or cannot af- ford to make, the tragic waste of manure by destructive disposal should be avoided whenever possible as a matter of public interest. SUMMARY Pages 3-8. California's animal produc- tion facilities are located mainly in the ir- rigated desert regions, the Central Valley, and warm coastal valleys. About half of the cattle in California feedlots are located in the warm, low-rainfall climate of the Imperial Valley. Dairies tend to be concen- trated in the periphery of metropolitan areas, and most poultry is raised in the San Joaquin Valley, Sonoma County, and along California's southern coast. Most of California's livestock are located in arid or semi-arid regions of the state which have distinct climatic advantages in drying manure for handling and nui- sance control. In more humid areas or where substantial quantities of water are used for sanitation or irrigation on the ranch, liquid manure handling systems can be advantageous. Most animal manures produced in Cali- fornia are currently being returned to the land. Profits derived from sales of manure depend on local supply and de- mand and can be negative in areas of highest animal populations. Pages 8-12. The quantity of manure pro- duced by domestic animals is related to the digestive characteristics and maturity of the animals and the rations fed. Post-ex- cretional changes in manures, especially with regard to contained water (which con- stitutes 80-90 per cent of the weight of fresh manures), have marked influences upon the weights of manure accumulations over periods of time. Pages 12-20. Chemical nutrients ingested by domestic animals, minus the amounts that appear in meat, milk, eggs, and other products, are excreted in feces and urine. Urine generally contains greater con- centrations of nitrogen, potassium, sodium, and chloride and lesser concentrations of phosphorus and magnesium than do the feces. Chemical compositions of manures may be altered dramatically by incorpora- tions of litter or soil and by decomposition during storage. Pages 20-24. Differences in the physical properties of various animal manures af- fect their handling characteristics and their potentials for influencing physical properties of soils amended with them. Poultry manures have relatively greater proportions of ash and lesser proportions of large fibrous particles than do other ma- nures, and the average particle density and bulk density of poultry manures are generally greater than for ruminant ma- nures. Animal manures are easily liquified and can be readily handled as slurries. Pages 25-36. The decomposition of animal manures is a continuation of digestion proc- esses. The easily-digestible portions of ma- nures are rapidly transformed and utilized by diversified microbial populations. Lig- nins and other resistant compounds are only slowly decomposed and remain in the soil as relatively stable humus. The oxy- gen status of decomposing manure has the greatest influence on the rate of decompo- sition and the character of the end-prod- ucts. Aerobic decomposition increases losses of total and plant-available nitrogen; the bio-oxidative process is rapid and pro- duces heat, and end-products are odorless and stable. Anaerobic decomposition is rel- atively slow and inefficient and some end- products are odorous and unstable, but it is easier to conserve nitrogen than in the case of aerobic decomposition. Decomposi- tion processes of solid or liquified manures 87 can be managed so as to achieve specific goals such as nitrogen conservation or nui- sance control. have to be taken into account. Hot com- posting of manure can kill most disease- causing organisms. Pages 36-45. Nuisances associated with manures are less noticeable when consider- ation is given to appearances of the ani- mal-production facility and to cultivation of good public relations. When animals and their wastes are located away from people, nuisance control is simplified. Zon- ing regulations are needed to accommodate confined animals and suburban citizens and to keep them both respectable dis- tances apart. Flies, odors, and dust are the main nuisances associated with animal manures, and the first two are more pre- valent in humid regions or where wet ma- nure is allowed to accumulate. Dust is more of a problem in arid areas. These three nuisances are minimized when ma- nure is managed so as to contain no more than about 25 per cent moisture. Moisture management is the effective key to nui- sance control. Pages 45-56. Water-quality criteria have been formulated to extend the availability of water to various water users. Manure and manure by-product additions to sur- face and underground waters by runoff, leaching, volatilization and reabsorption, or direct discharge can drastically change the quality of receiving waters, but feed- lots and barnyards can be managed to minimize water pollution. Animal confine- ment facilities located in semi-arid or arid regions may have distinct advantages in water-pollution control. The most effective method of controlling runoff and leaching of contaminants from land-spread manure is to adjust the amounts of manure applied to the land so as not to exceed soil and crop capacities for removing soluble nu- trients. Pages 56-62. Animal excreta including those of domestic pets and wild animals have been implicated in disease transmis- sion between animals or from animal to man. Some communicable diseases have been notably controlled by isolation and vaccination techniques, but salmonella and enteritis infections, among others, have been increasing especially among young animals. When considering animal manures as feed, disease organisms and their control Pages 62-66. The over-use or misuse of manure as fertilizer has resulted in salt toxicity, ammonia toxicity, and other prob- lems often blamed on manure itself rather than on mismanagement. For best results, manure used in crop production requires the same careful attention to rates of ap- plication, water management, and cultural practices that is given to application of chemical fertilizers. By so doing the bene- fits of judicious applications of manures outweigh the bothersome aspects of hand- ling them. Pages 66-75. Animal manures generally cannot increase short-term crop yields as much as equivalent amounts of nutrients supplied in refined chemical form. How- ever, these differences in yield are less with long-term usage. In California, nitrogen is most often the limiting nutrient required for maximum crop growth. Availabilities of manure-nitrogen are only about 30 to 40 per cent the first year, with smaller amounts of the original nitrogen becoming available in successive years. Nitrogen from manures can be utilized efficiently by starting with higher application rates in the first few years and decreasing applica- tions thereafter. The availability of phos- phorus and potassium in manures often ranges up to 90 or 100 per cent. Pages 75-82. The supplementary values of manure as a soil amendment should always be considered by those evaluating the worth of manure as a fertilizer. Animal manures contain a whole complement of plant micronutrients that can alleviate or prevent crop micronutrient deficiencies. Manure has also been shown to increase soil aggregation, aggregate stability, per- meability, and water-holding capacity (some soils respond more readily than others). Deleterious soil crusts can be ameliorated with manure additions and soil compactability can be reduced. Fi- brous ruminant or strawy manures gen- erally have more significant beneficial ef- fects on soil physical properties, but poul- try manures can also be helpful. There is some evidence that manure amendments encourage beneficial insects and microbes. Thus, in addition to nitrogen, phosphorus, 88 and potassium, manures have other values steam appears most promising. Research which should encourage their increased and development of this approach seems agricultural use and the conservation of highly advisable in this period of natural this valuable resource. gas and nitrogen fertilizer shortage. In California, where natural energy from sun Pages 82-86. Alternative uses of manures and wJnd c£m be substituted for purcnaS ed as animal feeds and energy sources are be- for (he deh dration of manures , ing investigated as means of extending the , . , P , r it* energy conversion techniques appear to be usefulness ol manure resources. Manures .j, , . f -i»i-» , . . . . . rapidly approaching economic feasibility contain substantial proportions ol the ong- . . , . , . , . . i <• • i r i li as costs ior conventional tuels increase. inal nutritive value of animal teed, and the feasibility of using manures as feed sup- Improving crop production is still the plements has been repeatedly demonstrated most Practical current use for most animal One possibility for practical feeding of manures. Initial planning for efficient ma- manure in California would be the proc- nu re handling and use abrogates the need essing of feedlot manures into feed supple- i° r highly complicated manure-disposal ments for range cows, which in turn would systems. Should practical technology be- distribute manure on open rangelands. come available for making use of the en- Of the several energy-from-manure ergy component of manures, management schemes, production of ammonia from ma- of some manures could be directed toward nure by forming synthesis-gas through conservation rather than bio-oxidation of partial combustion and reaction with the organic matter contained in them. LITERATURE CITED Anonymous 1968a. Status of solid waste management in California. Calif. State Dept. of Public Health, Sacra- mento. 8 sections. 19686. Water quality control and management in the Snake River Basin. Fed. Water Pollution Control Admin., Portland, Ore. (Sept. 1968). 1970. Position statement on animal waste management. Report of a special Dean's Task Force. Univ. Calif., Davis. 8 pp. 1970. Soil microorganisms break down DDT. Poultry Dig. 29:500. 1971. End product. Newsweek (July 26, 1971) 78:62-63. 1972. From agricultural wastes to feed or fuel. Chem. Eng. 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Pp. 263-70. 104 INDEX Abomasum 25 Aerobic decomposition 26-8, 34, 35, 87 end products of 27,28,33 Agricultural Park 37 Aluminum, in manures 16, 19 Amines, odors from manures 42 Ammonia 13, 17, 27, 28, 34 as a health hazard 38 toxicity to plants 64, 88 volatilization of 28, 32, 34, 35, 36, 53-4, 69, 74 from dairies 54 from feedlots 28, 34, 53 transport of 54 Ammonia synthesis 1, 85-6 Ammonium nitrate 67 Ammonium sulfate 67 Ammonium-nitrogen 27, 28, 32, 33 in soil profiles 53, 55 in feedlot runoff 51 Anaerobic decomposition 27-8, 87 effect of aeration on 42 effect on DDT degradation 81 effect on Fe and Mn availability 76 end products of 29, 32, 33, 34 odors from 42, 45 Antibiotics, effect on decomposition 36 in manure 36 Anthrax 57, 59, 60 Arsenic 65-6 fed to swine and poultry 66 in manures 16 in poultry litter 66 Ash 29,83,87 changes during decomposition 30 in feed vs. manure 15 in manures 16-7, 19, 20-1 Available water capacity 81 Barium, in manures 16 Bedding, effect on decomposition 36 particle size distribution 21 Beef cattle, availability of nitrogen in manures 71 BOD of manure 31 COD of manure 31 composting of manure 34 composition of manures 16-7 daily manure production 9 distribution of manure 10-1 distribution in California 3-4 husbandry 6, 44 manure's effect on hydraulic conductivity 79,80 manure produced per pound gain 11 manure produced per feed consumed 11 manure production with time 11 marketed from California 3 number in feedlots 2, 3, 87 number in California 3 nutrients excreted per production cycle 20 per cent of U. S. beef population 3 species of flies in manure 39 Biochemical Oxygen Demand (BOD) 29-30, 35, 46 aeration for odor control 40 of manures 31, 36 of runoff from feedlots 51 reduction with grassed area 54 Biological control (See Integrated control) Black blow fly 39 Black garbage fly 39 predation of fly larvae 40-1 role in integrated control 40-1 "Blue-baby disease" (see Methemoglobinemia) Blue blow fly 39 Boron, in manures 16, 65-6 Broiler (see Fryer, also Poultry) Brucellosis 59, 60 Caecum (Ceca) 25,26 Calcium 65, 76 distribution in feces and urine 14 effect of hormones on 18 in feed vs. manure 15 in manures 16-7, 19 recovery of 73 Carbohydrates, decomposition of 27 Carbon/nitrogen ratio 27, 69 changes during decomposition 35 Cats, in U. S. A. 3 Cation exchange capacity 32, 72, 76 Cattle (see also Dairy cattle, Beef cattle) as a disease reservoir 60-1 distribution of nutrients between feces and urine 14 Cellulose 82 changes during decomposition 30 decomposition of 26 Chemical fertilizers nitrogen 1-2, 6 Chemical Oxygen Demand (COD) 29-30 in runoff from feedlots 51 of manures 31 Chicken (see Hen) Chino-Corona Basin 4, 7, 19, 53, 54, 85 Chloride 87 distribution in urine and feces 14 in soil profiles 53 Coachella Valley 3, 67 Coastal fly 39 moisture requirements of 40 parasitism of 41 Cobalt, in manures 16 Coliform bacteria 57, 60 from animal sources 57 from human sources 57 Composting 34-5, 88 aerobic 35 anaerobic 34 effect on ash content 20-1 effect on nuisances 34 for disease control 62 Composts 27 and fly production 40 nitrogen in 34-5 survival of pathogens in 62 use as bedding or litter 86 weeds in 63 Copper 65, 66, 76 effect on decomposition 36 fed to swine 66 in manures 16 Copraphagous insects 34, 39, 42 Corral manures, chemical composition of 19 Corrals 23 Counteractants, for odor control 43 Cow (see Dairy Cattle) Crop 25, 26 Dairies, design 12 drylot 4 esthetic considerations 37 105 location in California 87 water disposal 12, 49 water use 5 Dairy cattle, availability of nitrogen in manures 71, 72, 74 BOD of manure 31 bulk density of manure 21-3 COD of manure 31 composition of manure 16-7 daily manure production 9 distribution in California 4 distribution of droppings 10 effect of hormones in manure during refeeding 84 flow of manure 23, 24 husbandry 12 manure production with time 11 manure produced per feed consumed 11 methane from manure 85 number in California 4 nutrients excreted per production cycle 20 odors from manure 42 reduction with aeration 42 particle density of manure 21-2 per cent of U. S. dairy cattle population 4 particle size distribution in manures 21 size of droppings 10 species of flies in manure 39 yearly manure production 4 yearly milk production 4 DDT 81 Decay series 71, 72 Decomposition processes 87 management of 87-8 relation to digestion 26 Deep-pit housing 5 Denitrification 28, 34, 35, 53, 55, 69 requirements for 28 Diet, U. S. A. 1-2 protein requirements 2 Diethylstilbestrol (DES) 18-9 in manures 66 Digestibility 10, 26, 82 Digestion processes 8, 17, 25-6, 82, 87 comparative physiology 25 effect of antibiotics 36 Direct discharge of wastes 48-9 Disease 88 associated with manures 59-61 dust transmission of 58, 59 hazards during refeeding 84 prevention of 61 chemotherapy 61 immunization 61 sanitation 61 Steps in transmission 57 transmission by flies 58 water-borne transmission of 58 Dogs, in U. S. A. 3 Drone fly 39 in feedlots 39 in holding ponds 45 moisture requirements of 40 Drying manures 87 effect on bulk density 22 for nuisance control 44 loe '- of nitrogen 32 Dry matter, distribution in feces and urine 14 Duck manure 44 Dust 88 from feedlots 43-4 control with sprinkling 44 relation to stocking rate 44 health aspects 38 in poultry houses 43-4 composition of 43 odor of 44 relation to moisture 43-4 moisture relationships 44-5 Eggs, U. S. consumption 2 number produced in California 5 Electrical conductivity (EC) 64 Erosion 81-2 Eutrophication, effect on BOD 47 effect on fish 47 Eacefly 39,58 False stable fly 39 Fat, decomposition of 26 in feed vs. manure 15 Fatty acids, effect of aeration on 42 relation to odors 42 Feathers 21 as a nuisance 45 Feces, as a proportion of total manure 10 composition of 8 Feed additives, effect on refeeding 84 occurrence in manures 84 Feed conversion 2, 8 Feedlot 2, 12, 19, 23 composting in 34 disposal of contaminated water from 49 flies in 39, 42, 44 management to reduce flies 39-40 moisture and dust 43-4 moisture and flies 39, 44-5 moisture management for pollution control 54-5, 88 odors from manure 42-3 soil atmosphere beneath 55 volatilization of ammonia from 28, 34 Fermentation 27, 32, 34, 74, 75 odors during 42 Fiber, in feed vs. manure 15 Field capacity 81 Fixed solids 20-1 Flesh fly 39 Flies (see also specific type) 5, 6, 34, 88 in feedlots 39, 42 health aspects 38 moisture requirements of 39-40 relation to stocking rate 39, 44 resistance to insecticides 40 role in disease transmission 38, 58 Fryer, BOD of manure 31 COD of manure 31 composition of litter 16 daily manure production 9 husbandry 5, 12 manure produced per feed consumed 11 number produced in California 5 nutrients excreted per production cycle 20 Gasification, of manures 85 Gizzard 25, 26, 62 Goats, as a disease reservoir 60-1 Grass tetany 65 Green blow fly 39 Guile 68 Hemicellulose 26,82 changes during decomposition 30 decomposition of 26 Hen, BOD of manure 31 bulk density of manure 21-3 ( !OD of manure 31 106 composition of litter 16 composition of manure 16-7 daily manure production 9 effect of ammonia on 38 flow of manures 23, 24 husbandry 5 manure's effect on hydraulic conductivity 79 manure produced per feed consumed 11 manure produced per product produced 11 manure production with time 11 number on California ranches 5 nutrients excreted per production cycle 20 particle density of manure 21-2 particle size distribution of manure 21 Hexestrol 18 Hippopotamus 46 Holding tanks 5 Holding ponds 6, 35, 49, 54 aerobicity of 43 irrigation from 35, 63-4 mosquitos around 45 salts in 63-4 sealing properties 35, 79 Horn fly 39 Hormones, effect on refeeding 84 in manures 66 in plants 66 use feeds 18-9 Horse 76 as a disease reservoir 60-1 BOD of manure 31 bulk density of manure 21 change in manure during decomposition 30 COD of manure 31 composition of manure 16-7 daily manure production 9 distribution of nutrients between feces and urine 14 species of fly in manure 39 Housefly 39, 40 and health 38 as a feed for chicks 83 copraphagy 42 in feedlots 39 moisture requirements of 40 parasitism of 41 survival in holding ponds 45 Humus 27, 29, 69, 75, 87 Hydraulic conductivity 79 Hydrogenation 85 Hydrogen sulfide, as a health hazard 38 odors from dairy manure 42 odors from manures 42, 43 Immobilization 69 Imperial Valley 3, 7, 39, 87 Infiltration 78, 79 in corrals 55 Insecticides, role in integrated control 40-1 Integrated control 40-1 Iron, in manures 16, 19, 65 Lagoon 35, 36, 49, 65 effect on water quality 49 for reduction of BOD 49 Larvicide 40 Leaching, from confinement areas 52-3 of manure 30, 32, 69 Leptospirosis 60 in recreation waters 58 Lignin 26, 29, 82, 87 changes during decomposition 30 decomposition of 26 Lignoprotein 27, 29 Liquid storage systems 11-2, 87 Little housefly 39,40 moisture requirements of 40 parasitism of 41 Livestock confinement areas (see also Feedlot) 3,8 flies in 39 health considerations 38 source of runoff 49-50 Magnesium 65, 76 distribution in urine and feces 14 in feed vs. manure 15 in manures 16, 19, 87 recovery of 73 Manganese, in manures 16, 19, 65 Manure handling 12 effect of climate 5-6 effect of physical properties on 23 Manure pellets 22 swelling of 23 Manure production 8-10 daily amounts 9 distribution of droppings 10-1 effect of confinement 8 effect of ration 10 per pound feed consumed 11 per pound product produced 11 size of droppings 10 Manures, accumulation with time 11, 87 alternative uses of 7-8 as a source of fuel energy 3, 84-6, 89 as a source of iron 76 as a source of manganese 76 as a source of zinc 76 as fertilizers 6-7, 88 consideration of quality 62 cumulative effects 67, 68 economics 1-3 effect of fermentation 32 effect of leaching 32 effect on soil and water pollution 56 rate of application 6 residual effects 67, 68-9 salt considerations 62-4 BOD of 31 bulk density of 87 chemical composition 16-7, 87 effect of storage 19 variation Avith moisture 17, 18 COD of 31 compression of 21-2 effect on bulk density 22 disposal of 6, 87 flowability of 23 heat value of 86 human 1 in surface waters, effect on dissolved oxygen 47 relation to fish kills 46-7 micronutrient values 88 moisture content 9-10 particle density of 87 physical properties of 87 quantity produced per acre of farmland 7, 87 ratio of animal to human 1 supply and demand 6-8, 87 use as bedding or litter 86 use as building material 86-7 Manure slurry 21 disease organisms in 59 irrigation with 5, 6 methane from 84-5 107 recovery of nutrients from 72, 73, 74 solids content 23 survival of pathogens in 59 uric acid in 32 Manure utilization, economic determinants 6-9 Manurial gases, health aspects 38 Marbling 18 Masking agents, for odor control 43 Meat, nitrogen in 12 phosphorus in 12 potassium in 12 Methane 27, 28, 29, 34, 55 dangers of 38 heating value of 85 production from manures 84-5 Methemoglobin 48 Methemoglobinemia 48 in U. S. A. 48 role of nitrate in 48 Milk, nitrogen in 12 phosphorus in 12 potassium in 12 Mineralization 28, 30, 71, 72, 74 Molybdenum, in manure 16 Mosquitos, as a nuisance 45 from manure holding ponds 45 Newcastle disease 58, 61 Nitrate 1, 27, 28, 32, 64-5 hazards to livestock 48, 64-7 hazards to man 48 in leachate from feedlots 52-3, 55 in runoff from feedlots 51 in soil profiles 52-3, 55 in well waters 52 Nitre spots 48 Nitrification 28, 35, 55 Nitrite 28, 32 hazards to man and livestock 48 Nitrogen 65 distribution in urine and feces 14 excreted during production cycles 20 farm-site requirements 2 fertilizer (see Chemical fertilizers) immobilization of 27, 35 in composts 35 in feed vs. manure 15 in manures 16-7, 18, 19, 63, 87 availability of 69-71 effect of handling on 74, 75 effect of hormones 18 fertilizer response 67, 68 recovery of 71-74 in natural waters 47 in relation to eutrophication 47 in runoff waters, from feedlots 51 from field-spread manures 56 in soil profiles 56 leaching from manure 30, 32 origins in feces 13 origins in urine 13 recovery in manures 13 release from organic manures 71-2 value for refeeding 82 Nitrogen-free extract ( NFE ) 15, 83 Nuisances 3, 62 control will) moisture management 44-5 effect of climate 44 moisture relationships 44-5 Odors 5,88 as a nuisance 44 effect of moisture 42-5 relation to aerobicity 42-3 Organic acids 76 Oxidation ditch 35, 83-4 survival of pathogens in 59 Oxidation-reduction potential (redox, Eh) 28, 34, 53, 55 Paraformaldehyde, for odor control 43 Parasites, of flies 41 Pathogens, resistance to drugs 61 survival of 59, 62 Pelleting manure 22 Permanent-wilting-percentage 80 pH, of poultry litter 28 of soil 28, 32 Phosphorus 65 availability and recovery of 88 distribution in urine and feces 14 excreted during production cycle 20 in composts 35 in feed vs. manure 15 in manures 16-7 30, 87 effect of hormones 18 fertilizer response 67 in natural waters 47 in relation to eutrophication 47 in runoff waters, from feedlots 51 from field-spread manures 56 leaching from manure 30, 32 recovery in manures 13 Pig (see Swine) Pink eye 58 Population equivalent (PE) 30 Potassium 64, 65 availability and recovery of 88 effect on soil physical structure 76, 79 excreted during production cycles 20 in composts 35 in feed vs. manure 15 in manures 16-7, 30, 87 in runoff from field-spread manure 56 leaching from manure 30, 32 recovery in manures 13 Potassium permanganate, for odor control 43 Poultry (see also specific type) 5 as a disease reservoir 60-1 arsenic in manure 84 availability of nitrogen in manures 71 composting of manure 34 dust and disease 38 location in California 5, 87 methane from manures 85 nitrogen in manures 13 odors from manure 42 separation from neighbors 37 species of flies in manure 39 U. S. consumption 2 Poultry litter, fertilizer value of 67 arsenic in 16, 66 moisture and dust 43-4 Poultry house, management to reduce flies 40-2 screening of 41-2 Protein, animal 1,13,17,18 changes during decomposition 30 decomposition of 26, 27 synthesis in rumen 25, 82 vegetable 1, 13, 17, 18 Protein anabolic compounds 18-9 Protein conversion 17-8 Protein-nitrogen 1, 27 Pumping manures 23 effect of solids content 23 Pyrolysis 85 108 Q fever 57, 61 Rabbits, as a disease reservoir 60-1 Rangelands 3, 6, 67, 83, 89 Redox (see Oxidation-reduction) Refeeding 89 effect on digestibility 83 effect on milk, meat, and eggs 83 limits to 83 of cattle manure 82-3 of poultry litter 83 of poultry manure 83 potential hazards of 84 problems in disease control 61-2 research needs 84 Rothamsted Experiment Station 68, 69, 70 Rumen 25, 82 Runoff 81-2 from corrals 23 quality from feedlots 51-2 effect of rainfall events 51-2 effect of slope 52 effect of surface material 52 effect of temperature 51 quality from field-spread manure 55-6 quality from rangelands 50 quantity from feedlots 50-1 effect of initial moisture 50 effect of lot physical design 50, 54 effect of rainfall 50-1 quantity from field-spread manure 55-6, 81-2 Sacramento Valley 3 Salinas Valley 3 Salmonellosis 38, 58, 60 from chicks 58 from feral animals 58 in feedlots 58 in feedlot runoff 58 in a manure slurry 59 Salts, effect on soil physical structure 76 injury to crops 63, 88 in lagoons and holding ponds 63-4 in leachate from feedlots 53 in manures 16-17, 19, 63 in soil profiles 56 management of 63-4 San Joaquin Valley 3, 6, 39, 44, 87 Separation of manure fibers 21, 36 effect on fly growth 45 reuse as bedding 86 Sheep, as a disease reservoir 60-1 BOD of manure 31 changes in manure during decomposition 30 COD of manure 31 composition of manures 16-7 daily manure production 9 distribution in California 4, 5 distribution of nutrients between feces and urine 14 loss of ammonia from urine 28 number in California 4 per cent of U. S. sheep population 5 Silicon, in manures 19 Slotted floors 49 Sodium 64 distribution in urine and feces 14, 17 effect on soil physical structure 76, 79 in feed vs. manure 15 in manures 16, 19, 87 Sodium chloride, as a feed additive 64 Sodium nitrate 72 Soil shrinkage 79 Stable fly 39 and health 38 in feedlots 39 Stabilization of manures, for odor control 43 Starch, decomposition of 26 Steer (see Beef cattle) Stockpiling 5, 30, 34 Strontium, in manures 16 Suburbs, in farming areas 3, 37 Sulfur, in feed vs. manure 15 in manures 16 leaching from manure 32 Swine, as a disease reservoir 60-1 availability of nitrogen in manures 71 BOD of manure 31 bulk density of manure 22 COD of manure 31 composition of manures 16-7 copper in manures 36 daily manure production 9 disposal of contaminated water from 49 distribution in California 4 distribution of manure 11 distribution of nutrients between feces and urine 14 effect of ammonia on 38 flow of manure 24 husbandry 11 manure produced per feed consumed 11 methane from manures 85 number in California 4 per cent of U. S. swine population 5 nutrients excreted per production cycle 20 odors from manure 42 species of flies in manure 39 Synthesis-gas 85-6, 89 Tetanus 56, 59, 60 Thin-spread drying 5 Thin-spreading of manure 45 effect on nuisances 45 Tarpaulins, for manure storage 45 Tuberculosis 58, 60 Turkeys, as a disease reservoir 60-1 BOD of manure 31 COD of manure 31 daily manure production 9 number produced in California 5 Urea 13, 25, 27, 30, 64 Uric acid 27,28,32,36 ammonia release from 13-4, 64 Urine, composition of 8, 87 as a proportion of total manure 10 Vitamins, synthesized in rumen 82 Volatile solids 20-1, 36 in runoff from feedlots 52 Wasps, parasitism of flies 41 Wastelage 83 Water pollution, manure management to minimize 87 Water quality, criteria 46, 88 effect of excess manure on 46 standards 46, 49 Zinc 16, 19, 65 Zinc deficiency, induced by manures 65 Zoning 38, 88 3m-8,'74(R6807i.)VL To obtain additional copies of this manual or a catalog listing other manuals and free publications available, see your University of California Farm Advisor (offices located in most California counties) , or write to: Agricultural Publications University of California Berkeley, California 94720 Orders of 10 or more copies of any one manual receive a 20 per cent discount off list price. 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