V° *'\" f '. Division of Agricultural Sciences UNIVERSITY OF CALIFORNIA '' c * Sudan § 1 aSS % 0SSeS mately 24 days. Thus? a delay in seeding ™ he ° ^ and don0t st ° o1 £ tlller as h from mid-May to early June would proba- ^ 1L Thl * characteristic in addition to bly delay a 30-inch growth by only about lar S er seed size 1S the r reason hi § her seed " 7 to 10 days. Early-season growth is ing rates are needed for these cultivars. dependent on soil and air temperatures, Seed wei g ht varies between cultivars, which vary from year to year. Experi- seed lot > and harvest years but the follow- < ments have shown that sorghum x sudan- in g is an approximation of the number of grass crosses do not have the ability to seed s per pound one may expect to find , germinate at lower temperatures than f° r the cultivars listed, sudangrass (Hart and Wells, 1965). 1 In gudan 23 4g 9QQ establishing a dryland seeding, optimum ' g^ ;;;;;; | soil temperatures may have to be sacn- T 1 4 *}9 100 ficed to insure adequate soil moisture at cv io on'onn t seedde P th - Sweet Sioux 16,900 How to plant The table below gives the ranges f Most acreage in California is planted by seeding rates within which most recom- broadcast methods or with a grain drill, mendations lie. Recommendations for Drilling assures better control over seed- broadcast seedings tend towards the high ing depth and seed distribution; produces end of the range while drilled seedings > i more uniform stands with less seed; and tend towards the low end of the range, generally outproduces broadcast stands. Generally, because rougher seed beds are * 1 See "Literature Cited for publications referred to in text by author and date. , [4] 2 o o <. UJ CM «5 O CM 03 OS O0 O CM -*i CM CO CM O O) (D t W CM -h rf CO .-< M M N rt rt 05 CO T CM CO CO M M Q. 5 <5 —■-""" or Early or late season growth 20 25 30 35 45 50 AVERAGE DAYS REGROWTH FROM LAST HARVEST [9] vested up to the boot stage of develop- ment will provide nearly twice the energy that is required for maintenance (Jung and Reid, 1966). For more mature sudan- grass, energy values drop rapidly to near- maintenance levels. The quality of feed produced, within the vegetative growth stages, can be enhanced by the judicious application of nitrogen. Figure 2 shows data obtained from trials with Piper sudangrass and illustrates the relationship between plant maturity, protein per cent, plant height, and yield. Variations can be expected between growth cycles — about5to 10 inches in leaf canopy height, 2 to 4 ± per cent points in protein, 0.75 to 1.0 ton dry-matter yield — depending largely on the season of growth and soil fertility. Early- and late-season growth can mature when it is at least 10 inches shorter than mid-season growth. This is presumably a daylength and/or temperature effect. Protein and yield will vary according to soil fertility and season — figure 2 affords an opportunity for relative comparisons of quality with yield. If the crop is to be grown only for maximum yield of rough- age, harvesting should be done at near maturity. Comparative productivity Table 4 summarizes the results of various clipping trials simulating pasture produc- tion. No single cultivar has been consist- ently the highest yielder, and the maxi- mum yield differences within years range from 0.15 to 1.51 tons of dry matter per acre. These trials were conducted on dif- ferent soils, and under different climatic conditions. Generally, the crosses will out- yield the sudan grasses in the first cutting or harvest of the season. After the first cutting the sudangrasses tiller profusely and the stand thickens, but the character- istic stand thinning and the development of larger stems by the crosses results in yields no greater than that of sudangrass. Table 4 COMPARATIVE SEASONAL YIELDS OF CULTIVARS WHEN CLIPPED TO SIMULATE PASTURE PRODUCTION Tons dry matter per acre per season Cultivar Davis Davis Kearney Field Station Davis 18" row Davis 24" row Fresno Sonoma Imperial Valley Field Station 1962* 1963t 1963J 1964§ 1964H 1965|| 1966** 1964ft Piper 7.63 7.55 7.15 7.42 7.14 7.10 7.20 7.27 6.5 6.4 5.9 6.5 7.11 7.15 7.26 7.18 6.73 6.22 5.79 6.62 6.29 6.12 5.55 5.18 5.36 5.81 4.64 4.64 4.93 4.83 4.75 6 77 Trudan 1 6 24 Trudan 2 Trudan 4 SX-11 6 42 SX-12 Sweet Sioux Greenlan 5.26 Suhi 1 Grazer 5 29 * Cut at 30' height, 3" stubble, 10 replications, 6 harvests. t Cut at 24-30" height, 3" stubble, 6 replications, 7 harvests. t Cut at 36" height, 3" stubble, 4 replications, 5 harvests. § Cut at 30" height, 3* stubble, 5 replications, 4 harvests. % Cut at 30" height, 3" stubble, 5 replications, 4 harvests. || Cut at 40" height, 6" stubble, 8 replications, 5 harvests. ** Cut at 40" height, 7" stubble, 5 replications, 4 harvests, ft Cut at 36-40" height, 4" stubble, 4 replications, 6 harvests. 50 lb. N applied preplant and after each cutting, except at Imperial Valley Field Station where 120 pounds pre- plant and 46 pounds after each cutting was applied. Not all available cultivars have been tested, but representative of the three types were included in most trials. [10] Q H g H PQ O m < H oq ^ W P > Ei n ° G co ^ W H <1 tf «1 Ph o u ■SPa 0,.-, W M O O k ic «) d oJ >> T3 -i -h V § £ w s § -^ — t— OS OS OS O o o °k m— OS lO M <5 O0 OS 00 00 o o o o o -2 2 fc5> b? 7? -2 £ os io W i-3 > o a « T5 . p M g >s°. ft be i -a M-5 c o o >> S3 ._ * fe As a consequence, under frequent har- vests there is little difference between the types. Findings of yield trials in other states, conducted over a number of years, can be summarized as follows: When cuttings are made four times per season or oftener (to simulate pasturing) hybrids and crosses are equal but not superior to the best su- dangrass varieties. When cuttings are made three times per season or less, hy- brids and crosses are superior in yield. When hybrids and crosses are harvested three times per season or less, they are usually in the heading or flowering stages of development when harvested. Because of their greater size and height the hy- brids and crosses, though requiring more growing time, will greatly outyield the sudangrasses. Two- and three-year aver- ages show no consistent yield differences among the crosses. When these cultivars are harvested only at later stages of maturity (late boot, head- ing, flowering, etc.) the hybrids are much taller (table 5) and will outyield the su- dangrass (table 6). The nitrogen applied in these tests apparently was close to the optimum amount for Piper sudangrass, considering the crude protein level for this stage of development. For the taller, longer- growing cultivars, 100 pounds of nitrogen per acre did not seem sufficient, as evidenced by lower crude-protein levels in the first and second harvests. These cultivars were running out of nitro- gen, and yields would doubtless have been slightly higher if 50 to 100 pounds of additional nitrogen had been supplied. There is no logical reason why the protein levels for these cultivars should not be about equal at the same stage of develop- ment, if adequate nitrogen were applied to compensate for the additional growing days and yield. Of particular interest is the vegetative growth in the third and fourth harvest periods. These plots had received the 100 pounds of nitrogen per acre after the pre- ceding harvest but had attained only 22 to 32 inches in height before the final har- vest. Note the rather high protein levels (table 6), which indicate a possible danger of nitrate poisoning. 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If the precautions listed below are followed, California pro- ducers should have little concern regard- ing prussic acid poisoning. • Let original growth or any re- growth of sudangrass attain at least 18 inches in height and the sorghum x sudangrass crosses 25-30 inches before using. • Do not turn hungry animals into short succulent pasture. • Be extremely cautions in using pas- tures that are recovering from either drought or frost. Prussic acid potential varies with crop years, within and between species, strains, varieties, and hybrids. Herbage is consid- ered safe if it contains less than 500 ppm of HCN; doubtful at 500 to 750 ppm; and dangerous above 750 ppm. These figures are only relative as the amount ingested is critical. Well fertilized sudangrass can contain about 2,000 ppm of HCN when 4 inches high, 1,200 ppm at 8 inches, 600 ppm at 16 inches, and 400 ppm at 20 inches (Boyd et al. 1938). Piper of the sudangrasses, and the Trudan series of hybrid sudangrass, are known to be un- usually low in prussic acid potential. On the other hand, sorghum x sudangrass crosses have been reported to range from 3 to 9 times higher than Piper in HCN con- tent (Harrington 1966). The potential HCN content for all cultivars decreases with increase in plant height and ma- turity. Once the forage has attained or passed the minimum safe height for usage, frost or drought has but little effect upon HCN content. Frost or drought has been shown to increase the already high HCN content of plants shorter than the minimum recommended height for use. If forage is at a safe height to feed prior to frost, it is safe after frost. The real danger in using frosted plants is not the affected plant material but the new growth shorter than the recom- mended minimum 18-30 inch height de- veloping from the crowns if warm weather follows a frost. Grazing animals will se- lect this new growth in preference to the frosted material. Nitrate Poisoning The increasing incidences of animal losses in California due to nitrate poisoning warrants a discussion of this hazard. Most losses occur because of the lack of under- standing by the operator that such a problem exists, what causes it, and what can be done to help prevent it. The fol- lowing suggestions are offered as meas- ures to lessen this hazard. • High luxury amounts of nitrogenous fertilizer is not only a waste of nitrogen but causes nitrates to accumulate within plants. • Sudangrass cultivars exhibiting an unusually dark-green color may contain abnormally high nitrate levels and should be suspect. • Many weeds common to California farm and irrigated pasture lands are known to accumulate high amounts of nitrate. These weeds have caused fatal poisoning of livestock feeding on other- wise safe forage. • Do not incorporate old, well-seasoned corrals and barnyards into annual pasture areas. Such sites are usually high in soil nitrates. • Avoid storing chopped forage in bank-out wagons to be fed next day or over a weekend. The nitrate in chopped green-moist forage, though in sub-toxic levels, can be reduced in substantial amounts by microbial action to the nitrite form within about 24 hours. The nitrite form is about 10 times as lethal as an equal amount of nitrate. • At times weather may influence the nitrate content of these forages. If during periods of very rapid growth, under high [13 luxury amounts of nitrogen, a drop in temperature or sudden overcast or cloudy condition develops, the growth rate is sharply reduced causing a temporary ac- cumulation of nitrates within the plants. •When forage is known or suspected to have accumulated lethal amounts of nitrate it can be used by diluting with other feeds tuffs. Accumulated nitrate in harvested forage is not dissipated by time or curing. If the forage is standing, delay pasturing or chopping, apply no addi- tional nitrogen, until the plants outgrow the condition. The nature of nitrate poisoning has been described as follows: When the ruminant ingests forage containing ni- trate, the microflora in the rumen reduce the nitrate to nitrite; convert the nitrite to ammonia; then to the amino acids. When this conversion is rapid, ingested nitrates will have little effect upon the ruminant animal. If the rate of or the amount ingested is more than the micro- flora can readily convert, nitrites accumu- late. The efficiency of the rumen micro- flora can be impaired through low avail- ability of carbohydrates, or their numbers reduced by the prior administration of antibiotics. The unconverted nitrite is readily ab- sorbed into the blood and is capable of changing normal hemoglobin to methe- moglobin which cannot transport oxygen from the lungs, and it is believed that the animal dies when oxygen in the tissue is depleted. This may require 3 to 6 hours, depending on the amount and rapidity of ingestion of the nitrate. Vital factors in nitrate poisoining are the nitrate content of forage, rate of in- gestion, and the condition of the animals. A rather small amount of plant material having a high concentration of nitrate (as in some weeds) can be lethal, while the same total amount of nitrate ingested over a longer period may cause no ill effects. Ingesting sublethal amounts of nitrate can, it is believed, cause failure to gain, loss in milk production, and abortion, though there is no conclusive proof as yet. There is little agreement throughout the United States, as to how much nitrate is toxic, dangerous, or safe. Some re- searchers suggest that the maximum safe amount in forage is 0.07 per cent NO s -N. (The nitrate content of feed is reported in several ways — as nitrate nitrogen (N0 3 -N), nitrate (N0 3 -) or potassium ni- trate (KNO3) — and may be expressed in parts per million (ppm or per cent (%).) See table below. Figure 3 shows that it would not be safe to apply any nitrogenous fertilizer under the conditions of an experiment conducted at Davis. Investigators at Cor- nell report that short-time experiments did not show abortion or loss in milk produc- tion when animals were fed hay contain- ing 0.57 per cent NO3-N. They also state that, as a general rule, forages containing more than 0.46 per cent NO s -N may be lethal when they are the sole component of the ration for cattle or sheep. Workers in a southern state, however, report no losses from forage containing 0.92 per cent NO3-N. Equivalents in per cent and parts per mil- lion when nitrate nitrogen is expressed as nitrate, and potassium nitrate. Nitrate Potassium nitrogen Nitrate nitrate NO3-N NO3- KNO3 0% ppm % ppm % ppm 0.70 7,000 = : 3.0 30,000 : = 5.00 50,000 0.63 6,300 = = 2.7 27,000 = 4.5 45,000 0.56 5,600 = = 2.4 24,000 = 4.0 40,000 0.49 4,900 = z 2.1 21,000 = 3.5 35,000 0.42 4,200 -. = 1.8 18,000 = 3.0 30,000 0.35 3,500 = z 1.5 15,000 = 2.5 25,000 0.28 2,800 = z 1.2 12,000 = 2.0 20,000 0.21 2,100 -. = 0.9 9,000 = 1.5 15,000 0.14 1,400 = = 0.6 6,000 = 1.0 10,000 0.07 700 -. = 0.3 3,000 = 0.5 5,000 As indicated previously, a total seasonal split application of 250 pounds of nitro- gen was about optimum for sudangrass used as pasture. Higher rates did not in- crease yields appreciably. Under normal conditions this rate of nitrogen applica- tion should be safe. However, 150 to 200 pounds of nitrogen applied preplant to taller, higher-yielding crosses grown to be harvested at the heading or flowering stage of growth could prove toxic or lethal if feeding plans were changed and the stand used for pasture or greenchop in the early or medium vegetative stage of [14] 0.70 0.63 0.56 0.49 ^ 0.35 y 0.28 ^J 0.2/ 0.14 0.07 0.0 a" /A / \ ■ A /A /00 LBS. N \ \ 300 LBS. N a \ \ \ 200 L8S. N > 250 LfiS. N i N > * 18 5 23 II 8 JULY AUG. AUG. SEPT. SEPT HARVEST DATE * 50 pounds preplant and after each harvest. Fig. 3. Nitrate nitrogen content of sudangrass pasture, on dry weight basis, resulting from five rates of applied nitrogen (harvested when approximately 30 inches tall). growth. Pasture growth containing sub- toxic amounts of nitrate may be grazed without difficulty but may be toxic when utilized as hay, greenchop, or silage, for these practices make it possible for ani- mals to consume a large quantity of feed in a shorter period of time. Publications recommended for further reading on nitrate poisoning are listed on page 16. Cystitis syndrome in horses The American Seed Trade Association, in cooperation with veterinarians at Texas A&M, has released the following informa- tion on cystitis: "There appears to be some evidence that sorghum x sudangrass type forage hy- brids as well as the sudangrasses, used ex- tensively for cattle grazing and greenchop may be injurious to horses. These widely used grazing and feed crops appear to be a factor in causing a cystitis syndrome in horses. The disease has been noted mostly in Texas and a few isolated areas of the southwest. It has been reported in Georgia, Alabama, Oklahoma, Washing- ton, Iowa, Kansas, California, and Ari- zona. Exact cause of the ailment has not been pinpointed, and thousands of horses have probably grazed these forage crops with no ill effects; however, horsemen should be warned of the danger and be cautious until continuing research can establish the exact cause of the syn- drome." Cattlemen, however, have no reason to become alarmed, according to the Texas A&M scientists, for no cystitis has been reported from grazing or feeding these forages to ruminants. [15] ACKNOWLEDGMENTS The authors gratefully acknowledge the cooperation extended by the Kearney Field Station and yield data supplied by George Worker, Imperial Valley Field Station. Literature Cited Boyd, F. T., O. S. Aamodt, G. Bohstedt, and E. Truog 1938. Sudangrass management for control of cyanide poisoning. Agron. Jour. 30:569-582. Hart, R. H., and H. D. Wells 1965. Effect of temperature and soils on emergence of summer annual forage grasses. Agron. Jour. 57:636-637. Harrington, Joseph, D. 1966. Hydrocyanic Acid Content of Piper, Trudan 1, and Six Sorghum-sudangrass Hybrids. Bull. 735. Agric. Exp. Sta. Penn. State University. Jung, G. A., and R. L. Reid 1966. Sudangrass. Studies on its yield, management, chemical composition and nutritive value. Bull. 524 T. Agric. Exp. Sta. West Virginia University. Reid, R. L., B. Clark, and G. A. Jung 1964. Studies with sudangrass. II. Nutritive evaluation by "In Vivo" methods. Agron. Jour. 56:537-541. Recommended Reading on Nitrate Poisoning The Nitrate Problem. Hanway, J. J., et al. Iowa State University. Special Re- port No. 34. Aug. 1963. Nitrate in Animal Feeds. Allaway, W. H., et al., Plant Food Review, Vol. 9, No. 3, Fall, 1963. Nitrates in Forage Crops and Silage. Crawford, R. F., and Kennedy, W. K. Cornell Miscellaneous Bull. 37. June 1960. Co-operative Extension work in Agriculture and Home Economics. College of Agriculture. University of California, and United Slates Department of Agriculture cooperating. Distributed in furtherance of the Acts of Congress of May 8, and June 30, 1 ( )1 I. George B. Alcorn, Director, California Agricultural Extension Service. 15m-10,'68(J2779)WP [16