Publication of T he College of *. i. -1 Methods, Equipment, and Costs Burt B. Burlingame y , ■■ * . ;< ^ ;.. JjjU'iPlflD A- ^y^^t£ri^ CALIFORNIA AGRICULTURAL it Station CIRCULAR 416 W A L N The front cover picture (also repro- duced here) shows a tractor- mounted knocking tower used in harvesting walnuts. This type of equipment is discussed on page 6. THESE ARE THE OPERATIONS COVERED Knocking and shaking 4 Hand knocking and shaking 5 Knocking from towers 6 Mechanical shaking 6 Cable shakers 6 Boom shakers 10 Picking 11 Hand picking 11 Use of hand rakes 13 Use of canvas sheets 13 Mechanical picking 15 THE AUTHOR: Burt B. Burlingame is Agriculturist (Farm Management) in Agricultural Exten- sion, and Associate on the Giannini Foundation of Agricultural Economics. [2] HARVESTING METHODS EQUIPMENT COSTS BURT B. BURLINGAME Walnuts are harvested in California by many different methods. Of these, no one method is considered the most efficient for all orchards. Efficiency is the result of properly balancing all operations — knocking and shaking, picking, hulling, and dehydrating. Good organization of crew, and timeliness and speed in han- dling nuts from shaking through drying are essential. CHOICE OF METHOD Choice is influenced by such factors as variety, size of trees, availability of sea- sonal hired labor, yield per acre, facilities for hulling and dehydrating, orchard acreage, planting arrangement of varie- ties, planting distance, available equip- ment, and climatic conditions. A survey of walnut-harvesting practices, conducted by the University of California Agricul- tural Extension Service during the 1951 season, showed how greatly these factors influenced the wide differences in current harvesting practices and costs. INFLUENCE OF HARVEST PRACTICES Quality of nuts produced and, there- fore, prices received are influenced con- siderably by harvest practices. Timeli- ness, for instance, is of prime importance in obtaining high-quality nuts. Darken- ing and molding of kernels, as well as staining of shells and freezing of kernels, can be minimized by prompt start of har- vest and rapid progress in getting all nuts harvested, as well as hauling them from orchard to huller and dehydrator. Nuts that are allowed to lie on the ground too long before picking are especially likely to mold and stain. Timeliness is essential in the Central Valley, where excessively early fall temperatures cause kernels to darken, and in the coastal areas, where fall rains cause mold and stain. Most growers interviewed in the 1951 survey planned to make changes in future operations, which it was expected would increase efficiency. Improved efficiency of methods and equipment can effect sub- stantial savings in cost and, therefore, result in higher net income. LABOR No specific crew size is the most effi- cient for all orchards, or necessarily even in the same orchard for the entire harvest season. Contract work for various opera- tions is common. Some growers contract a portion or all of the knocking or shak- ing, while others contract only picking. Some, for a fixed price, may contract all harvesting, including hulling, dehydrat- ing, and delivering to the processing plant. HARVESTING COSTS Records obtained by the Agricultural Extension Service on 80 orchards in 1950 showed harvesting to average more than a quarter of the total costs of production (table 1) . It accounted for more than 35 [3] Table 1 — Walnut harvesting costs per hundredweight compared with total production costs, 1950* Average Per cent total cost Total yield, pounds per acre 1,671 $ 3.01 1.04 19.6 6.7 Knock and shake, pick and haul out Hull, dehydrate, and deliver Total harvesting cost $ 4.05 $ 15.38 26.3 100.0 Total cost of production * Combined averages for 80 orchards in walnut management studies conducted by the Agricultural Extension Service in San Joaquin, Santa Clara, Stanislaus, Sutter, Tulare, and Ventura counties. per cent of all costs, except depreciation and interest. In many orchards, it amounted to more than 50 per cent of the total cash operating costs. Individual grower costs for all harvesting operations for the 1950 records showed a range of \\ f 2 cents to 5V2 cents per pound. The operations in the first phase of harvesting, which include knocking and shaking, picking, and hauling from the orchard, make up, on the average, about three fourths of the total harvesting costs. These are the operations mainly de- scribed in this circular. Wide variations in costs for these op- erations as shown by the 1951 survey (table 2) indicate that it is in this phase of harvesting that many growers can make substantial savings. KNOCKING AND SHAKING It is common practice to start harvest- ing operations as soon as the nuts can be hulled satisfactorily. In some districts, for some varieties, this may be as early as middle September. The nuts of some varieties — especially Concord and Payne — mature practically all at one time. Others, such as Placentia and Eureka, usually become hullable Table 2 — Summary of 1951 Walnut Harvesting Costs* General range Common or average Operations on a per acre basis Hand knock and shake with towers $26-33 10-46 9-40 12-30 65-90 45-85 20-60 10-35 $30 25 20 20 70 50 35 15 Shake with cable-type shaker — 2-man crew Shake with cable-type shaker — 3 or more-man crew Shake with boom-type shaker Operations on a per dry ton basis Hand knock, shake and pick Mechanical shaking on to canvas and haul out Hand picking only Mechanical picking * From a survey conducted by the Agricultural Extension Service, 1951. [4] over a period of several weeks. Two or more general pickings are therefore nec- essary in some orchards, especially in the coastal areas. In most orchards, particularly in the early part of the season, some nuts re- main even after the trees have been gone over thoroughly the first time, regardless of the harvesting method used. At the end of the season the remaining nuts usually are gleaned, but this practice depends on quantity, price, and weather conditions. Nuts are removed from the trees before natural fall by two general methods: 1) hand knocking or shaking with mallets and poles; and 2) shaking mechanically with cables or booms. Many different techniques are used with these methods. In recent years, mechanical shaking has replaced a large amount of hand knocking. However, considerable hand knocking and shaking, including the use of towers, is still practiced. Some grow- ers have tried mechanical shakers and have returned to the hand method. They were dissatisfied with broken tree limbs and damaged bark, the difficulty of get- ting a skilled shaking crew, and inability to save in cost. Certain varieties are more adaptable to mechanical shaking than are others. Hand poling from the ground fol- lowing mechanical shaking is a common practice. Pneumatic hand shakers from towers have been tried but without much success. HAND KNOCKING AND SHAKING Hand knocking is practiced by many growers whose orchard conditions are unadaptable to mechanical shaking. By this method, workers from the ground knock and shake off the nuts with poles of bamboo, wood, or aluminum. Workers also climb into the trees with mallets. One of the problems of hand poling (striking the branches with poles) is the breaking off of small twigs and branches. More leaves seem to fall to the ground with hand poling than with mechanical shaking. It therefore is usually a less de- sirable method for mechanical picking. Labor required. Shaking or knock- ing with mallets and poles is done most often on a contract basis. The method usually includes hand picking at a con- tract price for both operations. mm Hand knocking and picking in a walnut orchard. This method of harvesting is still used by many walnut growers in California. [5] Costs. In orchards visited during the 1951 season, contract rates for hand knocking and picking generally ranged from $65 to $90 per ton of dried nuts. Rates usually were so much per sack of nuts knocked and picked. Hauling from orchard to huller and dehydrator was additional. In only one orchard visited was hand poling reported separately, on a contract basis. This was at a low rate per tree, which approximated only $13.50 per acre. Trees in this orchard were of medium height. KNOCKING FROM TOWERS Knocking towers are a good, practical method in orchards of tall trees unadapt- able to other systems of knocking. Many different types of towers are used. Some are mounted directly on a tractor, while others are mounted on a wheel chassis and pulled by tractor. Towers vary in height from 20 to more than 40 feet. Some operators mount frames below the towers to deflect falling nuts from the tracks or wheels of equipment. Also, a few growers use catching frames and de- vices with the towers. One of the main problems in the use of towers is the mov- ing between and around the trees with minimum damage to branches and to nuts on the ground. Labor required. Usually three to five positions for knockers are provided on the towers. In addition to the knockers is a tractor driver and sometimes one man knocking from the ground. Thus, a knocking-tower crew consists of four to seven men. Costs. Data obtained indicate that tower knocking probably is costlier than either straight hand poling, shaking, and knocking, or mechanical shaking. Costs ranged from $24 to $30 per acre, exclu- sive of depreciation and interest over- head on the towers. Such overhead would be minor — probably around $2 to $3 per acre — if the acreage were sufficiently large to keep towers operating during the entire harvest season. Costs per pound of nuts harvested in high-yielding orchards might not be any more than by other methods in lower-yielding orchards. MECHANICAL SHAKING During the past ten years mechanical shaking of walnuts has gradually re- placed hand work. No data are available on proportion of total acreage mechan- ically shaken, but it is relatively large in some districts. The proportion is ex- pected to increase, but mechanical shak- ing is not likely to replace all hand work. In some orchards shaking or knocking by hand from the ground or in the trees and from towers may remain the most efficient methods. CABLE SHAKERS Most of the mechanical shakers used in the northern California and Central Valley districts are cable rather than boom type. Shaking action is obtained by an eccentric driven either by a power takeoff or by an auxiliary engine mounted on the tractor. Shaker mech- anisms are mounted either toward the rear or to the front of the tractor. Both wheel and track-type tractors are used. In the survey, more track types were ob- served. Growers seem to prefer their greater weight and maneuverability. Some growers have equipped old tractors for shaking and use them only for that purpose. Most growers, however, de- mount the shakers at the end of the har- vest season, so that the tractor can be used for other work during the rest of the year. Most shakers in use are of the local machine-shop variety that has been adapted to a particular tractor. The shaker, which is usually belt driven to reduce shock on the tractor, carries its own flywheel. The eccentric stroke is about li/2 inches at 500 rpm or 2 inches for slower speeds. Where the shaker mechanism is located at the rear of the tractor, a rod is often extended to the front before the wire cable is attached. [6] Left. Over-all view of a cable shaking opera- tion. (See page 8 for close-ups.) Below. Cable shaking setup, with platform 2 mounted on tractor to eliminate climbing trees jj to attach hook. Sling of 8-ply belting attached directly to cable Most slings are of Manila rope. Light-weight hook which can be placed on tree from the ground by means of rod. [7] This reduces whipping of the cable. Some shakers are arranged so that the cable runs over one or more pulleys to the eccentric. Shakers may operate continuously while the tractor is running, or they may be shifted in and out of gear if the mech- anism permits. Some shakers are rigged up with a mechanism that gives a knock- ing action along with the shaking. Some operators claim that such action in- creases the effectiveness of the shaker. One commercially built cable-type shaker is mounted on an independent chassis. Desirable features of this type are self- alignment, cable takeup, and moveability with other than tractor power. Under certain conditions, some hand poling from the ground may follow shak- ing. When only one shaking is practiced, a followup with a hand poling of out- side branches is often necessary, particu- larly early in the season. Some varieties, such as Eureka, are more difficult to shake than others. Also, size and struc- ture of tree influence the effectiveness of shaking. Such hand-poling labor is usu- ally part of the shaking crew. Wire cables. The system used deter- mines whether the wire cable should be long or relatively short. Most growers have the cable long enough to extend somewhat beyond the spread of the tree. Long cables generally allow more limbs to be shaken from one tractor position than do short cables. In the survey, cable sizes ran from %e inch to V2 inch in diameter. Many grow- ers considered the lighter-weight cables easier to handle and, therefore, capable of speeding the operation. However, more care and skill in handling the trac- tor are needed with light-weight cables to prevent their excessive breakage. Size of Types of cable shaking mechanisms. In next to bottom picture, note wooden blocks between tractor cleats to prevent cutting up ground that was smoothed for mechanical picking. Bottom picture is self-aligning shaker that can be pulled by light truck or tractor. tree as well as kind and weight of tractor also are factors to be considered in de- termining the best cable size. Hooks and slings. Hooking the cable to the limbs of the tree is done in a num- ber of different ways. A common method is to hook the cable to a sling. The sling is placed around the limb by a man in the tree. In some instances the tractor driver hands the hook on the end of the cable to the worker in the tree, but many growers find that two or more men, be- sides the tractor driver, increase the effi- ciency of operation. To facilitate getting the cable to the man in the tree, a rod of light-weight material is sometimes attached to the end of the cable. The hook is on the other end of the rod. When the cable is hooked to limbs from a platform on the tractor, a longer rod, of course, is required. Some growers run the cable through a pipe or tube, which is just strong enough to hold the cable stiff while it is being handed up to the worker in the tree. Size of trees and distance from ground to lower limbs more or less influence selection of the best method to use in getting the cable into the trees. The hooks attached to the ends of the wire cables or rods are usually large enough to place over the limbs. Hooks currently made are usually of light- weight metal. Most slings are made of Manila rope, although a limited number of operators use belting material that is connected di- rectly to the cable instead of to a hook. Not all growers agree on the best type of sling or the best size of rope. Some have tried large-sized rope and discarded it for a webbing of smaller-sized rope, while others have done just the opposite. Efficiency in handling, limb bruise, and sling breakage are the principal factors in determining the kind of sling to use. Several slings are often set in a tree be- fore the cable is passed up. Such practice speeds up the operation where two men are used in the trees. Labor required. With a cable shaker at least two men are needed: a tractor driver and a man to handle the cable, hook, and the slings that are used. Data obtained from the survey, however, indi- cated that the two-man crew was usually less efficient than a crew of three or four men where climbing of the trees was re- quired. In general, the more continuously the tractor operates the more efficient is the operation. The size of the shaking crew is in- fluenced by whether or not previously fallen nuts must be raked from the path of the tractor wheels or tracks. Spread of the trees in relation to planting distance, length of cable, and quantity of nuts that fell prior to shaking are factors bearing on this. Keeping the cable free of tractor tracks or wheels when moving is another factor that must be considered in deter- mining crew size. Costs. Cable-shaking equipment was found to range from about $50 for simple shopmade attachments to more than $1,000 for manufactured shaker units. Upkeep and replacement costs of cables in 1951 were figured by some growers at about $2 per day of operation. Cost per acre for mechanical shaking of a low-yielding orchard is practically the same as for a high-producing or- chard, other conditions being equal. Rec- ords obtained in the walnut-harvesting study showed a wide variation in cable- shaking costs. The range was from $9 to $46 per acre and from $10 to $52 per ton of dried nuts. All records averaged about $22 per acre. The cost per ton was also $22, since the average yield of this group was roughly a ton to the acre. Costs in orchards where three or more men were used in the crews showed an average of about $20 per acre and per ton, compared with about $25 for those using two-man crews. In orchards of medium-sized trees, 30 to 40 feet tall, cable-shaking costs of the more efficient operators ran from $12 to $16 per acre. [9] One of a number of different kinds of boom-type shakers operating in an orchard. BOOM SHAKERS Boom-type mechanical shakers have been in use almost as long as cable type. Even so, the number in operation at the present time is relatively small compared with the cable type. This is probably due to the fact that design limits their adapt- ability to different orchard conditions and that they are more expensive to re- pair. In some southern California dis- tricts, however, they are used more extensively than the cable type. The earlier boom shakers were custom built to individual specifications. Their designs varied a great deal, as did their efficiency. Some were discarded after limited use; others have been in use since they were built, usually with certain im- proved modifications. Commercially built boom shakers are now available, these considerably improved over earlier mod- els. Especially has the use of auxiliary engines increased their efficiency. Some of the modern shakers still are custom built. Timeliness is a favorable point to the boom shaker. The grower has more con- trol over the time when he wishes to shake and can more easily adjust his shaking to fit the operations of picking, hulling, and drying. Tree size and structure are important considerations in the adaptability of a boom-type shaker to a given orchard. In some orchards, trees have been trained in a way that makes getting into and around the branches with a particular shaker very difficult. Some growers have even considered changing the pruning practices to allow easier access with a boom shaker. Such changes are an in- dividual problem requiring careful thought. Although considerable progress has been made in the design of boom-type shakers, many growers feel that further improvement must be made before the boom type will become more popular than the cable type, where both are adaptable. In Ventura County, however, where repeated shakings are required in orchards, the boom type is the most popular. Labor required. The principal ad- vantage to the boom shaker is its one- man operation. The grower who operates [10] the shaker himself eliminates the neces- sity of hired labor for that particular job, and the problem of obtaining and keep- ing a skilled shaking crew busy. At times an additional man may be needed to rake nuts away from the tractor wheels or tracks or to hand-knock outside nuts not brought down by the shaker. As with cable shaking, a skilled op- erator is needed to prevent excessive bruising and breaking of limbs. A little more skill is probably needed to manipu- late a boom-type than a cable-type shaker for the same degree of efficiency. Costs. Cost data obtained from grow- ers operating boom-type shakers ranged from $12 to $30 per acre. Indications are that under equally adaptable conditions and an equal degree of operating ef- ficiency, boom-shaker costs per acre ap- proximate cable-shaker costs. PICKING To retain maximum quality, walnuts should be picked soon after knocking and shaking. The longer the interval between shaking and drying, the greater the risk of a higher percentage of dark kernels, mold, and stain. Especially does rain injure nuts left on the ground too long before picking. These are the main reasons why growers try to shake and pick only the quantity that can be hulled and dried each day. Some growers have learned from experience that when wal- nuts are allowed to stand in sacks, boxes, or bins — sometimes even for a day — be- fore hulling and drying they lose quality. This condition can be worse in the early part of the season, when hulls are on more nuts and moisture content is higher than later in the season. In past years all but a very small pro- portion of the walnuts were picked by hand from the ground. Different kinds of rakes have been used by pickers with varying degrees of success. Knocking and shaking onto canvas sheets or catching frames have been practiced by a few growers for many years, but certain limitations to these systems have kept them from becoming very popular. Me- chanical pickers have been in the de- velopmental stage for a number of years, but until 1951 accounted for a very minor portion of the walnuts harvested. In 1951 an estimated 5 to 7 per cent of the crop was harvested with mechanical pickers. HAND PICKING Common practice is to hand-pick into buckets which, in turn, are emptied into sacks and sometimes into lug boxes. The number of pickers required in a given orchard usually depends on hulling and drying capacity. For efficient operation, hulling and drying capacities should be adequate to handle the expected maxi- mum production of a given orchard when spread out over an estimated, safe har- vesting period. The length of harvest season may vary considerably between orchards because of differences in varie- ties. Advantages. Compared with other methods of picking, the advantages of hand picking are: 1) nuts can be picked free of clods, rocks, leaves, and twigs; 2) ground requires less leveling and smooth- ing than for mechanical picking; 3) in- vestment in picking equipment is lowest possible; and 4) crew can be adjusted to existing conditions. Disadvantages. Some of these are: 1 ) requires more seasonal workers, which involves the problem of getting and keep- ing pickers until harvesting is completed ; 2) less dependable from standpoint of getting nuts picked when they should be picked; and 3) costlier than other adapt- able methods. Rates of performance. According to records obtained from growers in both 1950 and 1951, the quantity of walnuts picked per worker per day in different orchards varies widely. Yield per acre and condition of ground were the prin- cipal factors affecting such differences. It is also recognized that considerable dif- [ii ference may occur between individual workers in the same orchard. Records showed the number of sacks picked per adult worker per day to range from about 18 to 35. Earlier in the season, when more hulls stick to the nuts, workers will usually pick more sacks per day, but there will be a smaller number of nuts per sack than later in the season. Even though the num- ber of sacks picked per day decreases during the season, the quantity of actual hulled and dried nuts tends to remain fairly steady, other factors being equal. In weight of dried nuts, adult pickers average about ^ to % ton per day in orchards with fair-to-good picking con- ditions. Labor required. Once harvesting be- gins, most growers try to complete it as rapidly as possible. The number of pick- ers needed to gather the daily quantity of nuts required is affected by the rate of picking per worker. Since little skill is needed to handpick walnuts from the ground, most any worker can be used regardless of pre- vious experience. Entire families, there- fore, often work in the walnut harvest. The heavier jobs, such as hand knocking and shaking, where practiced, are done by men, while women and children work at the picking. Specially designed hand rakes are used to put nuts in position for mechanical picking, or for one method of hand picking. Costs. Figures from growers for the 1951 harvest season showed rates paid for hand picking alone to range from about 35 cents to 65 cents per sack or- chard run. This did not include knocking or gleaning. Some growers pay a flat rate per sack for their whole orchard, except for glean- ing, during the entire season. This is usually a contract with a picking crew, and often includes a bonus of so much per sack for those staying until the end of the season. A method of this kind re- sults in fluctuating earnings during the season. However, it generally figures out at a seasonal average about as good for the worker, or better, than the rate that varies during the season according to picking conditions. Growers who vary their rates paid per sack, box, etcetera, usually try to do so in a way that more or less tends to keep daily earnings of workers fairly constant through the season. Such rates are gen- erally sufficiently high to allow good workers 25 per cent or more per day higher earnings than if paid at an hourly rate. In a given orchard, rates may be varied for picking different varieties ac- cording to differences in yields. Hand-picking costs in 1951 for or- chards on which data were obtained ranged from $20 to $60 per ton of dried nuts. Most of the orchards with yields of around 1,500 pounds or more per acre showed costs of between $25 and $35 per ton. When hand knocking and pick- ing were contracted together, rates ranged from $65 to $90 per ton of dried nuts. HAND GLEANING Nuts that fail to drop during normal knocking and shaking operations may be picked up later in the season after they drop. This so-called gleaning varies from orchard to orchard and from year to year in the same orchard. Such variables as quantity of nuts to be picked, quality, market value, going wage rates, and weather conditions late in the season de- [12] termine whether a grower will find gleaning profitable. Labor required. A number of grow- ers contacted in the 1951 season esti- mated gleanings to average about 10 per cent of the crop. Some growers hire work- ers at an hourly rate for gleaning, while others pay on a piece-work basis or even on a share basis. Rates paid for gleaning in the 1951 season for a number of the orchards studied approximated an equiv- alent of $100 per ton of dried nuts. USE OF HAND RAKES Smooth ground surface is necessary if hand rakes are to be used effectively. This need may call for extra, preharvest smoothing operations. Nuts raked into rows or piles may be forked or scooped into containers. Separation of leaves, twigs, clods, and rocks from the nuts may require supplemental equipment with this system. Hand rakes are used to advantage in removing nuts from the path of wheels or tracks of knocking and shaking equip- ment. More recently they have been used to draw nuts away from tree trunks and from other places into position for me- chanical picking. USE OF CANVAS SHEETS The fact that over the years so few walnut growers have used either canvas sheets or catching-frame equipment in- dicates that only under rather limited conditions were these methods desirable. Some growers who have tried canvas sheets have returned to conventional hand picking as a more practical method for their conditions. Other growers have used canvas to advantage for a number of years. Recent developments in me- chanical picking probably will mean even less use of sheets and catching frames in the future. The sheets are usually spread beneath the trees just before knocking and shak- ing. Either two rectangular sheets, twice as long as wide, or four square sheets Use of canvas sheets under trees has never been popular with California walnut growers. [13] may be used per tree, depending upon tree size. Weight of the canvas limits the size that can be handled efficiently by the workers. One grower interviewed successfully used four sheets 30 x 30 feet for trees with a 50-foot spread. This grower used two sets of sheets so that while nuts al- ready on one set were being rolled up into boxes, shaking could be done on the other set. Some operators rig up the canvas sheets to be emptied into low sleds which, in turn, permit bulk han- dling of the nuts. Certain factors determine whether canvas sheets can be used to advantage. Availability of good working crew: Good workers for handling canvas are usually more difficult to obtain than hand pickers. Quantity of nuts dropped prior to knocking and shaking: If very many nuts need to be hand-picked from the ground the advantage of canvas is soon lost. Yield per acre: Low-yielding or- chards require approximately the same man-labor per acre to handle the canvas as high-yielding orchards. The labor to harvest two sacks per tree by this method would be about the same as for six sacks per tree. Size of orchard and varieties: Or- chard must be large enough to keep workers busy during harvest season and to warrant the overhead cost of the can- vas. Proportion of total crop that can be harvested in one time over: The cost of handling the canvas usually makes it impractical for use more than one time over the orchard during the season. Unless most of the nuts can be harvested at that time, the advantage of the system may be entirely lost. Efficient way of removing leaves and twigs: Except for large twigs and small branches that can be picked out quickly by hand, some supplementary mechanical equipment is usually re- quired. Blowers and squirrel cage screens are generally used. Ability to coordinate with shak- ing: Operation should be so organized as to allow both shaking crew and crew handling canvas to work without inter- ruption. Labor required. Three men in the mechanical shaking crew and five han- dling the canvas sheets seemed to be an efficient combination for the operator previously mentioned. Costs. The relatively few records ob- tained on the use of canvases showed a range of $55 to $100 per acre for the complete operation of shaking, picking, and hauling to the huller. Costs for the same operations on a per ton basis ranged from $45 to $85. These figures include overhead costs of depreciation and in- terest on equipment. The cost of just the picking phase of the operation, one time over, for one orchard in the study A catching frame, mounted on a portable knocking tower. [14] was approximately $30 per acre. This included depreciation and interest on canvas and on other special equipment. USE OF CATCHING FRAMES These have been tried to an even lesser extent than canvas sheets on the ground. Usually the catching frame and a knock- ing tower are mounted on the same chassis. The limitations applying to the use of canvas sheets in general apply to the use of frames. In addition, the bulkiness and heaviness of the equipment must be con- sidered, as well as the greater investment. Costs. Little data on the cost of using catching frames were obtained in the study. One operator used equipment of this type mainly for early knocking of outside nuts of certain varieties. This was followed by a regular mechanical shak- ing when the remaining nuts on the trees were ready for harvest. This grower be- lieved that the higher price received for the better quality of the outside nuts more than paid for the cost of the addi- tional operation. The actual cash oper- ating cost for this operation was figured at 12 cents per sack. Overhead costs of depreciation and in- terest on the tractor and rig would vary according to the number of sacks har- vested. On this particular orchard, weather conditions in some years did not permit much use of this equipment. MECHANICAL PICKING Although tried experimentally in dif- ferent ways for some time, only in the last couple of years have mechanical pickers for walnuts really started to come into their own. Increasing wage rates and scarcity of harvesting laborers in recent years undoubtedly have been important factors tending to accelerate the develop- ment and perfection of such machines. Also, the fact that other crops, such as almonds and prunes have been found adaptable to mechanical picking has helped to encourage development. Several makes of pickers are available to growers at the present time. It is not the purpose of this circular to go into detailed engineering aspects of the various pickers or to try to point out advantages or disadvantages of different designs and principles of operation. The main object here is to attempt to cover some of the important cultural and eco- nomic relationships in the use of these machines; and to point out certain limit- ing factors or problems that have been encountered in their use. At the present time it appears that mechanical picking of walnuts is here to stay. Some believe that in the relatively near future most of the walnuts in the state will be harvested in this way. Data obtained in the 1951 harvesting study showed that, in some orchards, present- day mechanical pickers can harvest wal- nuts more economically than any system previously used. This study also dis- closed the need for considerable readjust- ment of practices in some orchards be- fore mechanical pickers can be used ef- fectively. In a number of orchards visited, where machines were being tried for the first time this year, growers were having difficulties with lack of proper ground preparation and supplementary equip- ment. Some growers who purchased ma- chines in 1951 did not try to replace previous methods entirely in one season. Instead, they spent the harvest season in learning how to use the machine; deter- mining what supplementary equipment was needed for efficient operation under existing conditions; and determining what harvest organization would give the best results. Some mechanical pickers are self-pro- pelled, while others are built for mount- ing on common makes of light tractors. There are advantages to both systems. To answer the question of whether or not to purchase a self-propelled machine or one that can be operated with a tractor, al- ready owned, a grower needs to consider [15] his field-power equipment available for use at harvest time in relation to his over- all system of harvesting. Both the me- chanical shaking and the hauling of nuts from orchard to huller require field power. Some growers have old tractors that are used only for shaking. Under such conditions the tractor used for tillage operations may be used to run a picker. However, in many orchards the tractor is somewhat larger than is needed or desir- able for running a mechanical picker. Also to be considered is the need, some- times, for more than one mechanical shaker if sufficient nuts are to be brought down for the most efficient use of the picker. It is apparent, therefore, that in many orchards the shifting to mechanical pick- ing will require additional field power. Whether this should be a self-contained machine or another tractor for mounting a picker depends mainly on the use which might be made of such a tractor for other work. Balancing various harvesting op- erations. Of primary importance in effi- cient mechanical harvesting is the proper balancing of the various operations. Ex- cept under special conditions, there is no advantage to shaking more nuts than can be picked, hulled, and dehydrated in a day's time. In most orchards the capacity of the dehydrator is the limiting factor determining the quantity of nuts har- vested per day. The size of the dehydrator has often been decided on the expected maximum tonnage from an orchard, divided by the usual number of days in the harvesting season. This allows maximum use of de- hydration facilities and lowest possible overhead costs per ton. Also, stretching the harvest season over the longest prac- tical period makes the greatest use of operator's time and family labor and thereby tends to keep hired labor costs to a minimum. As a result, the capacity of the majority of the walnut dehydrators is less than four tons. Thus, it is obvious that a large proportion of the orchards in the state at present do not have the production nor the facilities to utilize a mechanical picker to its fullest efficiency. Because of this, two or more growers under certain conditions might be able to work out a cooperative deal whereby a mechanical picker could be used on a larger acreage and supply nuts for two or more existing dehydrators. Obviously, a number of factors limit this type of ar- rangement, but where applicable it would be of definite advantage. Some growers may rent pickers to neighbors. Enlarge- ment of present hulling and dehydrating facilities is planned by some growers who already have mechanical pickers. This will allow more rapid harvesting and thus tend to improve the average quality of the nuts for the season. It is quite probable that as mechanical pick- ing becomes better established, contract operators will handle many smaller or- chards on which the ownership of a picker cannot be justified. In shifting to mechanical picking, shaking is likely to become a bottleneck in some orchards. This may occur be- cause, under most conditions, one me- chanical picker will pick up nuts faster than one mechanical shaking crew can cover the orchard. Preparing the ground. It is gen- erally agreed that for efficient operation of mechanical pickers, the ground sur- face should be as smooth and free of clods and rocks as is possible. One make of machine may do a better job than another of separating nuts from foreign material, but the efficiency still is lowered with increasing amounts of clods and rocks. The amount of extra tractor work re- quired to put the ground in proper con- dition will vary considerably between orchards. Soil type is an important in- fluencing factor. The amount of necessary floating, dragging, and rolling often de- pends on the timing of the operation in [16] A smooth ground surface is im- portant for efficient mechanical picking. Here are two of the many kinds of rigs used for smoothing the ground surface. .- relation to the optimum moisture content for best working of the soil. Sandy soils, of course, are much easier to prepare for harvesting than clay. An additional two to four times over, in different directions, with a relatively large float, drag, or leveler and roller usually is sufficient treatment in some or- chards to put the ground in good condi- tion for mechanical picking. Added costs of such operations are about $1.50 to $3.00 per acre, including overhead on the additional equipment needed. Even if the costs on soils more difficult to smooth were twice these amounts, they would usually be more than offset by the advan- tage to the mechanical picker. Supplemental equipment. Until mechanical pickers are built to separate leaves, twigs, clods, and rocks completely from the nuts during the picking process, additional equipment will generally be needed to remove such foreign material. This equipment is usually tied in with the hulling operation. Kind of equipment and use depend to a certain extent upon in- dividual orchard conditions. Orchards on sandy soils will not have the problem of clods found on the heavier soils. However, rocks may be a factor. Much experimental work in developing this special machinery was done by grow- ers and manufacturers in the 1950 and 1951 seasons. The machinery is now fairly well perfected to handle the most common situations, but it does not elimi- nate the need for good ground leveling and smoothing prior to harvesting. Separation of twigs and other material smaller in diameter than the nuts usually has been done with a squirrel-cage type of revolving screen. Other devices have been used successfully but generally re- quire more man labor. Extra blowers are used sometimes to remove quantities of dry leaves. excessive [17] MECHANICAL EQUIPMENT Shown on these pages are four of the different commercially produced mechanical pickers. It appears that an increasing proportion of walnuts will be harvested with such machines n future years. [18] FOR PICKING WALNUTS Insets in this picture and the one opposite show close-up views of actual picking mechanisms. All such machinery requires careful smoothing and leveling of the ground surface prior to picking. [19] Mechanical rake used for getting nuts into position for mechanical picking. Removing clods and rocks within the diameter range of the nuts so far has been done mainly with a washer or water bath in which the nuts are separated by flotation. This method has certain limi- tations, especially in the volume of clods or rocks that can be handled. Rakes used prior to mechanical pick- ing can also be considered as supple- mental equipment. Hand rakes are a relatively small cost item compared with mechanical rakes. The problem of tak- ing care of large quantities of wet leaves may involve other equipment, such as a side delivery rake. Rates of performance. The rate at which mechanical pickers will pick up walnuts depends to a certain extent upon the quantity within a given area (yield per acre), the condition of the ground surface, the amount of other foreign ma- terial, such as leaves, twigs, and branches that must be eliminated or handled in the process, and the number of men in the crew in relation to the optimum number required to keep the machine operating at maximum capacity. No attempt was made at the time of this study to draw any conclusions on differences in rates of picking between different makes of mechanical pickers. All machines observed during the 1951 harvest season appeared to have a satis- factory picking capacity under favorable operating conditions. Actual rates of picking observed in 1951 ranged from about Y2 ton to 1% tons of dried nuts per hour. In a number of instances, where only one picking was required, except for gleaning, the normal average for the sea- son was considered to be about one ton per hour. At this rate, approximately 25 to 30 hand pickers would be replaced by a machine. All machines were built so that the for- ward motion could be speeded up when the quantity of nuts on the ground was smaller. Thus, the rate of picking could be held fairly constant within a rather wide range in yields. [20] The number of acres picked per hour ranged from one to two for pickers on which data were obtained in 1951. Varia- tions in rates were due mainly to factors listed above. Labor required. Mechanical pickers are operated by one man. If the nuts are sacked instead of bulk-handled, an addi- tional man is usually required on the rig. Even in bulk handling, an extra man in some instances may ride the trailer to distribute the load, to help unload, and to pick out large pieces of foreign ma- terial, such as twigs, clods, and rocks. In addition to the one or two men on the machine, most operators contacted in 1951 employed one or more men to rake nuts away from tree trunks and some- times to windrow nuts from the tree rows so that the picker could be run in a straight path. Such workers usually re- move sizable branches and twigs from under the trees, thus assisting in the smooth operation of the machine. The three-man crew seemed to be the most common among growers using me- chanical pickers in the 1951 season. It should be pointed out, however, that in most instances machines were used to one half or less of their capacity in terms of operation hours. Only one grower inter- viewed used his machine near capacity and here two men were required to keep ahead in the raking. Effectively used by some growers were specially designed, wide hand rakes with skids allowing a certain amount of clear- ance from the ground. Also, some grow- ers in 1951 experimented with special machine attachments designed to elimi- nate hand raking. Small, powered rakes for getting nuts into position for machine pickers are now being built commercially. As the organization of mechanical picking improves, the amount of man labor for the operation may become less than at present and the normal-sized crew would be lower than the three men indi- cated. One man more or less in the me- chanical-picker crew, however, would not change the picking cost per ton very markedly if the rate of picking were one ton per hour. Efficient use of labor. Not only must the various operations of shaking, pick- ing, hulling, and drying balance but, at the same time, efficient operation calls for a good balance in the harvesting crew. Ideally, of course, all members of the harvesting crew should be fully occupied, with no loss of time nor waste of effort, whether working on an hourly or on a piecework basis. In most orchards, man-labor require- ments for the different operations usually vary to a certain extent during the sea- son. Early in the season more man labor may be required for knocking or shaking in relation to picking. Thus, some mem- bers of the crew are normally shifted from one operation to another when help is needed to keep operations in balance. This is easier to do in hand knocking and picking because of the larger number of workers. However, in shifting to mechanical picking considerable adjustment in the labor force is necessary. Obtaining an efficient crew balance is one of the main problems involved, especially in orchards where operation of the machine is limited to only two or three hours a day. Whether or not a grower has his own huller and dehydrator also will influence labor bal- ance. Costs of mechanical picking. Costs will vary considerably between orchards. Factors accounting for differences in such costs per ton include the following: 1) original cost of picker; 2) rate of de- preciation; 3) number of tons picked per season; 4) number of men in picking crew; 5) operating costs per hour, in- cluding repairs; 6) rate of picking — acres per hour; 7) yield per acre; 8) condition of ground surface — soil type; 9) cost of leveling and smoothing; and 10) investment in supplemental equip- ment and operating cost. From the limited data obtained in [21] COSTS OF MECHANICAL PICKING OF WALNUTS — PER HULLED AND DRIED TON, AT VARYING TONNAGES HARVESTED PER SEASON 70 65 60 55 50 45 | 40 i_ 0) o. 35 «/» L. o "o 30 a 25 20 15 10 5 1 V 25 50 150 175 200 75 100 125 Tons picked per season Based on a self-propelled picker at an original cost of $4,500 plus supplementary equipment valued at $1,000, in the assumption that one ton per hour would be picked with a three-man crew. Man labor is $1.25 per hour. Extra soil preparation required for mechanical picking would be additional to above cost figures. Hauling out of orchard also is additional. 1951 the cost curve (shown above) was prepared. This curve is believed to ap- proximate average efficiency for a given set of conditions. It shows the relation- ship between picking cost per ton and tons picked per season. Some operators undoubtedly will have lower costs than those shown, while other operators will probably have higher costs. The assumptions indicate that mechan- ical-picking costs per ton are approxi- mately $35 when about 25 tons are picked per season. With 50 tons picked during the season, the cost per ton drops to around $20. As previously noted, hand- picking costs in 1951 generally fell be- tween $25 and $35 per ton. Thus, machine picking would begin to compete with hand picking when the number of tons picked per season was within the range of 25 to 40 for the conditions stated. This, therefore, would mean that where yields averaged a ton to the acre, minimum-sized orchards on which a me- chanical picker could probably be justi- fied would be somewhere between 25 to 50 acres. If yields per acre were only 1,000 pounds, then twice the acreage would be required. Future improvements in machinery and techniques probably will result in mechanical-picking costs being even lower relatively to hand-picking costs than at present. [22] EFFICIENT HULLING AND DRYING FACILITIES ARE ALSO IMPORTANT IN KEEPING COSTS LOW A bulk handling setup for mechanically picked nu ts. A— pit where nuts are dumped; B— ele- vator from pit; C— squirrel cage to eliminate trash; D— washer to eliminate rocks and clods; E— elevator from washer; F— huller; G— elevator for hulls. Photograph at right shows nuts be- ing dumped into pit. Close-up of a washer. A— Nuts en- ter; B— twig remover; C— rocks and clods conveyed out from bot- tom of tank; D— paddle forces nuts over to conveyor; E— nuts conveyed out of washer, usually to huller. [ 23 ] The cost of supplemental equipment will vary a great deal between growers. Some operators are known to have in- vested at least $1,000 in such equipment. Therefore, for purposes of figuring over- all costs of mechanical picking, the overhead on $1,000 of supplemental equipment has been included in figure 1. Gleaning with mechanical pick- ers. In gleaning, mechanical pickers ap- pear to offer several advantages over hand picking. Timeliness is an important factor in the gleaning operation. Speed in gleaning often has considerable in- fluence on quality because of increasing weather hazard as the season progresses. It sometimes determines how much gleaning can be done. In most orchards a mechanical picker would probably cover the ground in a fraction of the time required by a hand-picking crew that could be obtained late in the season. An- other advantage is that when the quantity of nuts is too small to warrant hand pick- ing, gleaning with a mechanical picker might pay. The principal disadvantage to depend- ing on mechanical pickers for gleaning would be in early rains, when the ground was too wet for the machine to be used. Costs of mechanical gleaning. Of first importance is lower costs per pound of nuts gleaned, assuming the ground was originally prepared for mechanical picking. Such costs, of course, would vary according to yield as well as to a number of other obvious factors. Whether over- head cost of depreciation and interest on equipment were prorated to the gleaning operation or were charged entirely to the main harvesting would have a bearing on the calculated total cost. Most oper- ators probably would figure only operat- ing costs of gas, oil, repairs, and man labor. Under such conditions the cost of gleaning for many growers would figure $3 or less per acre. Thus, if 150 pounds of nuts were gleaned per acre, the cost per pound would be 2 cents or less com- pared with a probable 5 cents or more for hand gleaning in 1951. ACKNOWLEDGMENTS This publication was made possible through the help and cooperation of many walnut growers, manufacturers of walnut-harvesting equipment, the California Wal- nut Growers Association, and members of the staff of the College of Agriculture. Sincere appreciation is expressed to all who contributed information, suggestions, and pictures. The author also wishes to acknowledge special help from A. W. Christie, 0. L. Braucher, and R. J. Gotelli of the California Walnut Growers Association; E. F. Serr of the Division of Pomology; Roy Bainer of the Division of Agricultural Engi- neering; R. R. Parks, Extension Agricultural Engineer; A. D. Rizzi, Extension Pomologist; and County Farm Advisors A. G. Volz, F. M. Charles, J. H. Foott, M. R. Bell, H. A. Weinland, and G. E. Goodall. In order that the information in our publications may be more intelligible, it is sometimes necessary to use trade names of products or equipment rather than complicated descriptive or chemical identifications. In so doing it is unavoidable in some cases that similar products which are on the market under other trade names may not be cited. No endorsement of named products is intended, nor is criticism implied of similar products which are not mentioned. Co-operative Extension work in Agriculture and Home Economics, College of Agriculture, University of California, and United States Department of Agriculture GO-operating;, Distributed in furtherance of the Acts of Congress of May 8, and June :!0, 1914 .' Karl Coke, Director. California Agricultural Extension Service. 10m-9,'52(A22S7)MIl [24]