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Glycine max (L.) Merr.

Fabaceae
Soybean

Source: James A. Duke. 1983. Handbook of Energy Crops. unpublished.

  1. Uses
  2. Folk Medicine
  3. Chemistry
  4. Description
  5. Germplasm
  6. Distribution
  7. Ecology
  8. Cultivation
  9. Harvesting
  10. Yields and Economics
  11. Energy
  12. Biotic Factors
  13. References

Uses

Seeds furnish one of the world's most important sources of oil and protein. Unripe seeds are eaten as vegetable and dried seeds eaten whole, split or sprouted. Processed they give soy milk, a valuable protein supplement in infant feeding which also provides curds and cheese. Soy sauce made from the mature fermented beans, and soy is an ingredient in other sauces. Roasted seeds used as a coffee substitute. The highly nutritious sprouts are readily consumed in Asia. Seeds yield an edible, semi-drying oil, used as salad oil and for manufacture of margarine and shortening. Oil used industrially in manufacture of paints, linoleum, oilcloth, printing inks, soap, insecticides, and disinfectants. Lecithin phospholipids obtained as a byproduct of the oil industry, used as a wetting and stabilizing agent in food, cosmetic, pharmaceutical, leather, paint, plastic, soap, and detergent industries. Soy meal is very rich protein feeding stuff for livestock for which there is an increasing demand. Meal and soy bean protein used in manufacture of synthetic fiber, adhesives, textile sizing, waterproofing, fire-fighting foam and many other uses. Soy flour prepared from the whole beans, producing a full-fat flour with about 20% oil, that from mechanically-expressed meal gives low-fat flour with 5–6% oil; that prepared from solvent-extracted meal gives defatted flour with about 1% oil. The flour is used in bakery and other food products; and as additives and extenders to cereal flour and meat products, and in health foods. The vegetative portions of plant used for silage, hay, pasture or fodder, or may be plowed under as a green manure. The straw can be used to make paper, stiffer than that made from wheat straw.

Folk Medicine

Old Chinese herbals suggest that the soybean was a specific remedy for the proper functioning of the bowels, heart, kidney, liver, and stomach. A decoction of the root is said to be astringent. The meal and flour are used to prepare diabetic foods due to the small amount of starch contained therein. Soybean diets are valued for acidosis. Since soybean oil has a high proportion of unsaturated fatty acid, it is recommended, like safflower, poppyseed, etc. to combat hypercholesteremia. Commercial grades of natural lecithin, often derived from soybean, are reported to contain a potent vasodepressor. Medicinally lecithin is indicated as a lipotropic agent. Soybean is listed as a major starting material for stigmasterol, once known as an antistiffness factor. Sitosterol, also a soy byproduct, has been used to replace diosgenin in some antihypertensive drugs.

Chemistry

Raw seeds of Glycine max have been reported to contain per 100 g, 139 calories, 68.2% moisture, 13.0 g protein, 5.7 g fat, 11.4 g carbohydrate, 1.9 g fiber, 1.7 g ash, 78 mg Ca, 158 mg P, 3.8 mg Fe, 0.40 mg thiamine, 0.17 mg riboflavin, 1.5 mg niacin, and 27 mg ascorbic acid. Sprouts contain per 100 g (edible portion): 62 calories, 81.5% moisture, 7.7 g protein, 1.8 g fat, 8.0 g total carbohydrate, 0.7 g fiber, 1.0 g ash, 52 mg Ca, 58 mg P, 1.1 mg Fe, 30 mg Na, 279 mg K, 25 mg b-carotene equivalent, 0.19 mg thiamine, 0.15 mg riboflavin, 0.8 mg niacin, and 10 mg ascorbic acid. Dried yellow seeds are reported to contain 400 calories, 10.2% moisture, 35.1 g protein, 17.7 g fat, 32.0 g carbohydrate, 4.2 g fiber, 5.0 g ash, 226 mg Ca, 546 mg P, 8.5 mg riboflavin, and 2.2 mg niacin. The Wealth of India (C.S.I.R., 1948–1976) indicated the mineral composition (percentage on fresh weight basis) 2.09 K, 0.38 Na, 0.22 Ca, 0.0081 Fe, 0.0012 Cu, 0.24 Mg, 0.59 P, 0.02 Cl, 0.0032 Mn, 0.406 S, 0.0022 Zn, and 0.007 Al; I, Mo, B, Ni, and Si are also reported. Green feed of soy contains 12.56% fiber, 23.7 fiber, 52.1 N-free extract, 2.2 ether extract, 1.9 CaO, 0.57 P2O5, 1.4 MgO, and 2.4% K2O. The hay contains 15.0% crude protein, 29.1 fiber, 42.6 N-free extract, 1.3 ether extract, 12.0 total ash, 2.9 CaO, 0.60 P2O5, 1.2 MgO, 0.3 Na2O, and 2.0% K2O. Soybean straw contains 16.0% moisture, 7.4 protein, 2.0 ether extract, 28.3 N-free extract, 26.1 fiber, and 10.2% fiber. Nutritional analyses of dozens of soybean products appear in the Food Composition Table for Use in East Asia. The sprouts, now popular among health fadists, contain 86.3% water, 6.2 protein, 1.4 fat, 5.3 carbohydrates, 0.8 ash, and per 100 g sprout, 48 mg Ca, 67 mg P, 1 mg Fe, 180 IU vitamin A, 0.23 mg thiamin, 0.20 mg riboflavin, 0.8 mg niacin, and 33.8 mg vitamin C. Soybean lecithin contains 11.7% palmitic acid, 4.0 stearic, 8.6 palmitic, 9.8% oleic, 55.0 linoleic, 4.0 linolenic, and 5.5% C20 to C22 acids (including arachidonic). A globulin, glycinine, accounts for 80–90% of the total nitrogen protein of the seed. Glycinine contains 1.1% cystine, 1.8 methionine, 5.4 lysine, 1.7 tryptopbane, 2.1 threonine, 9.2 leucine, 2.4 isoleucine, 4.3 phenylalanine, 3.9 tyrosine, 2.2 histidine, 1.6 valine, 8.3 arginine, 0.7 glycine, 1.7 alanine, 5.7 aspartic acid, 19.0 glutamic acid, and 4.3% proline. Glycine has been reported to contain betaine, choline, guanidine, hydrocyanic acid, isovaleraldehyde, maltose, oxalic acid, saponin, trigonelline, and tryptophane.

Description

Bushy, rather coarse annual herb; stems up to 1.8 m tall, sometimes vine-like, terete toward the base, more or less angled and sulcate to subquadrangular above, grey brownish or tawny, hirsute to pilose with pale hairs; leaves pinnately trifoliolate, their petioles 2–20 cm long, from subterete and sparsely pilose or glabrescent to strongly angled, sulcate and hirsute, the rachis 0.5–3 cm long, the stipules broadly ovate, abruptly acuminate, 3–7 mm long, conspicuously several-nerved more or less strigose; leaflets membranous, broadly ovate, suborbicular, oval or elliptic-lanceolate, 3–14 cm long, 2.5–10 cm broad, the terminal seldom appreciably larger than the lateral which is usually more or less inequilateral, generally acute but frequently obtuse and mucronulate, occasionally deltoid-acuminate, tapering to rounded or subtruncate at base, usually sparsely silky-strigose on both surfaces or glabrate above, occasionally rather densely strigose-velutinous below, their petiolules 1.5–4 mm long, usually densely hirsute, stipels narrowly lanceolate to setaceous, 1–3.5 mm long, bracts from broadly to narrowly lanceolate 4.5–5.5 mm long, several-nerved, strigose; racemes axillary, irregular, often leafy, very short, 10–35 mm long, usually rather compactly few-(5–8) flowered, the peduncle and pedicels often reduced and concealed by a densely hirsute vesture, the flowers sometimes single or paired in the lower axils; bractlets from broadly to narrowly lanceolate, 2–3 mm long, strigose, caducous; flowers on usually densely hirsute to glabrescent pedicels 0.25–3 mm long; calyx 5–7 mm long, setose to appressed-hirsute or strigose, the teeth subequal, lanceolate to lanceolate-attenuate, the upper pair generally united to above the middle the bracteoles setaceous, appressed, setose, 2.5–3.25 mm long; corolla white, pink, greenish blue, violet or purple, 4.5–7 mm long, the standard suborbicularobovate to subreniform, emarginate, somewhat longer than the narrowly oblong wings which much exceed the keel, porrect or somewhat upturned near the apex; pod oblong, subfalcate, pendant, 25–75 mm long, 8–15 mm broad, coarsely hirsute or setose, the bristly hairs up to 2.5 mm long, yellowish-brown; seeds 2–3 per pod, ovoid to subspherical or irregularly rhomboidal, 6–11 by 5–8 mm, greenish cream or grayish-olive to reddish black, smooth, the caruncle scalelike, membranous, erect or appressed, about one-third to one-half the width of the hilum. Fl. summer, fr. fall; varying as to locality.

Germplasm

Plants extremely variable and many varieties and cultivars named or developed, bred for resistance to diseases, for flowering-time control, climatic and edaphic conditions and oil or protein content. Agricultural agents should be consulted for the best local cv. Thirty-six trivial variants have been described as subspecies and varieties, and many horticultural cvs have been developed. Several germplasm collections of soybean are described in Hill (1976). Assigned to the China-Japanese Center of Diversity, soybean or cvs thereof is reported to exhibit tolerance to aluminum, bacteria, disease, frost, fungi, hydrogen flouride, high pH, heavy soil, insects, laterites, limestone, low pH, mycobacteria, nematodes, photo- period, pesticides, smog, smut, and viruses. (2n = 40).

Distribution

Widely cultivated, not known in the wild state. Believed to be a cultigen from Glycine ussuriensis, reported to grow in China, Japan, Korea, Russia, and Taiwan.

Ecology

A subtropical plant, but its cultivation extends from the tropics to 52°N. In the US it has its greatest development in the corn belt. I observed it as one of the more frequent cultivars at 47°N in Nan Char, People's Republic of China. It will not withstand excessive heat or severe winters. A short-day plant. Requires 5 dm water for good crop. Grows best on fertile, well-drained soils, but does tolerate a wide range of soil conditions; pH 6.0–6.5 preferred. Soybean soils must contain the proper nitrogen-fixing bacteria. When grown on the same land for 2–3 successive years, increasing yields are obtained year after year. Crop suited to a dry zone, to a low or mid-country wet zone or under irrigation. Soybeans will brow better than many crops on soils that are low in fertility, droughty or poorly drained. Many high latitude cvs do very poorly in low latitude. Ranging from Cool Temperate Moist to Wet through Tropical Very Dry to Wet Forest Life Zones, soybean has been reported to tolerate annual precipitation of 3.1 to 41.0 dm (mean of 108 cases = 12.8), annual mean temperature of 5.9 to 27°C (mean of 108 cases = 18.2), and pH of 4.3 to 8.4 (mean of 98 cases = 6.2).

Cultivation

Propagated by seed. Seedbed preparation for soybeans is similar to that for corn or cotton, requiring very thorough cultivation to provide a deep loose seedbed. Fall or early spring plowing is preferred by most growers to plowing immediately before planting. Important that weeds be destroyed by light disking, thorough harrowing or by use of cultivators, immediately preceding planting, thus preventing the weeds from getting ahead of the soybeans. Soil temperatures and day-length determine the best time to plant seeds at or (after corn-planting time in most areas). Full-season cvs, which take most of the growing season to mature, produce highest yields when planted with or soon after corn. Rate of seeding varies with the area: in northern US, narrow rows 46–68 cm wide produce the highest yields, in southern US there is little advantage in rows closer than 90 cm for spring plantings. Soybeans are often planted with planters designed for other crops but adapted for soybeans by special plates. They are sometimes planted with a drill in which all the feed cups are covered except those needed for row planting. A row planter provides more uniform depth of seed (should be 2.5–5 cm). Seeding rate depends on cv or size of seed, width of row and germination of seed. A good rate is one seed per 2.5 cm of row. Close spacing encourages rapid growth of soybeans and aids in weed control, but spacings closer than 2.5 cm may seriously increase lodging. Excessive lodging causes difficulty in combining and reduces yields. Seeds are often treated to protect them from soil-borne diseases. Seeds can be treated any time before planting, even in the preceeding fall at harvest. Soybeans need inoculation with a commercial culture of nitrogen-fixing bacteria unless the bacteria are known to be in the soil. Soybean bacteria live in the soil a number of years. Some farmers do not inoculate if nodulated soybeans have been grown there in the past 4–5 years. Inoculants from other legumes are not effective on soybeans. In the absence of nodulation, soybeans require nitrogen fertilizer for maximum yields. Soybeans fit well into many rotations, with corn, small grains or other legume; or in rotation with cotton, corn or rice or planted after early potatoes and vegetables, or after winter grain; or planted when grass clover or row crops have failed. Fertilizer needs vary with the soil and the cropping system. Soil tests will indicate specific needs. Fertilizer often is applied to other crops in the rotation and soybeans may not need additional fertilizer. On soils of low fertility, fertilizers increase yields. If plants are modulated properly, nitrogen fertilizer is not needed. Fertilizer containing potash is injurious to germination when in direct contact with the seed. Fertilizer may be applied in bands 5–7.5 cm to the side and 5 cm below the seed; or soil and fertilizer may be mixed if 2.5 cm is left between fertilizer and seed. Broadcast fertilizer should be plowed under or disked in. Soybeans are more acid tolerant than other legumes but will respond to lime applications on acid soils. Weed competition is serious, and may reduce yields by 50%. Early cultivation prevents weeds from becoming established ahead of the soybeans. Both rowed and drilled soybeans can be cultivated effectively with a rotary hoe, drag harrow, or weeder. This equipment may be used even before the soybeans have emerged. Soybean plants are easily injured by cultivating equipment just before and during emergence from the soil. After emergence there is less danger of breaking the stems if cultivation is done during the hot part of the day. For final cultivation, row cultivating equipment is used. Cultivation should be no deeper than required to destroy the weeds, and should be discontinued when cultivation causes damage to the plants. In Taiwan, handweeding doubled the yield as compared to the weedy control, (1600 vs 800 kg/ha). Alachlor, (2 kg/ha), chloramben (2), linuron (0.25), and nitrolen (3 kg/ha) also doubled the yield, the first two being most effective at controlling weed grasses. Soybeans are usually not grown under irrigation, at least in the US. A good crop usually requires about 50 cm of water. In most areas where soybeans are grown, moisture is adequate. Soybeans tolerate dry soil conditions before they bloom, but drought during the pod-filling stage seriously reduces yields and seed quality. During this stage, supplemental irrigation produces the most successful results. Contour of the land largely determines the type of irrigation. Row or flood irrigation may be used on land that has been leveled and prepared for it. Heavy, infrequent irrigations usually give better results and require less labor than frequent light irrigations. Time between irrigations depends on the type of soil and the weather. The practice of double cropping of soybeans, usually by alternating with a small grain crop such as barley or wheat, has increased in warmer regions of the US. Typically two crops are obtained per year by seeding small grain in fall and harvesting in Spring. Immediately after harvest, soybeans are seeded to utilize the summer growing season. Both conventional plowing and "no till" planting in the small grain stubble are widely used. Technological improvements in planting equipment, better herbicides, and early maturing cultivars of small grains have contributed to the increased use of double cropping.

Harvesting

All seeds on a soybean plant mature at essentially the same time. Maturity of the seed is accompanied by a rapid dropping of the leaves and drying of the stems. Combines should be adjusted frequently during the day so as to reduce losses due to splits and mechanical damage to the seeds. Harvesting loss can amount to 10–20% of the crop during combining. Combining seed for planting requires special care to prevent mechanical damage. As seed moisture drops below 12%, germination damage because of mechanical injury increases. The best combine cylinder speed threshes properly but does not crack seed. Soybeans require clean, dry bins for storage. The most important function of good storage is to control moisture content. If the storage period is for one year, the moisture content of every load should not be higher than 11% for a 5 year storage, no higher than 10%. Excessive moisture may cause molding, heating, and spoiling. If they are kept dry, beans will not deteriorate appreciably in quality for a year or more. Viability deteriorates rapidly if seed is stored beyond the first planting season following harvest. Soybeans make a versatile emergency hay crop because they are adapted to a wide range of planting dates. They should supplement and not substitute for alfalfa, clover or other hay crops. Soybean hay is difficult to cure and loss of leaves and spoilage during curing may reduce quality. There are many good hay or forage types of soybeans, which usually have fine stems and small, dark-colored seed. When drilled 5–7.5 bu/ha (136–204 kg/ha), soy cvs can equal forage cvs in quantity and quality of hay production. Time to cut soybean hay ranges from the time the pods begin to form to the time when the seeds reach full size. A widely used guide in harvesting soybean hay is to cut during the first favorable weather after the seeds are half developed. A common method of curing soybean hay is to leave it in the swath 1 or 2 days, then rake it into, small windrows. Unless drying conditions are good, the windrows may need turning once or twice before the hay is ready to bale. A roller-crusher attachment on the mower will hasten the curing process because crushed stems lose moisture more rapidly than intact stems. Soybeans require 75–200 days, depending on cv and region.

Yields and Economics

Soybean hay yields average 5 MT/ha. Average yield of beans is about 1700 kg/ha (60 bu/ha). High-yielding cvs, adapted to the locality and grown under proper culture and favorable conditions will yield more than twice the average yield. Some farmers have produced yields of more than 125 bu/ha (3400 kg/ha). In Taiwan, TK-51 irrigated with 200 MT H2O/ha yielded 3.1 MT/ha beans; and 7.6 MT DM/ha compared to the control with 2.8 MT beans and 7.1 MT DM. World production of soybeans in 1970 was 46,521,000 MT grown on 35,019,000 ha, yielding 1330 kg/ha. North America produced about 31 million MT; Mainland China, 11.5 million MT; Latin America, 1.9 million MT; South America, 1.1 million MT; Asia, 1.2 million MT. Economically, this is the most important grain legume crop in the world. World production in 1975 was 68,356,000 MT on 46,463,000 ha, averaging 1471 kg/ha. North America led with 42,317,000 MT, of which the US, averaging 1909 kg/ha, produced 41,406,000 MT. Asia excluding Russia produced 13,727,000 MT, averaging 828 kg/ha. South America produced 11,109,000 MT, averaging 1759 kg/ha. Russia produced 600,000 MT, averaging 750 kg/ha. Europe produced 442,000 MT, averaging 1369 kg/ha, Africa 96,000 MT, averaging 482 kg/ha, Oceania 64,000 MT, averaging 1404 kg/ha. China was estimated to be second to the US, producing 12,062,000 MT, Brazil third with 10,200,000 MT, Indonesia fourth with 560,000 MT, Mexico fifth with 545 MT. New Zealand's reported yields were highest at 3000 kg/ha, Canada 2322, Paraguay 2160, Turkey 2000, Colombia 1913. In 1975 the effective demand for oilcake was growing faster than for fats and oils. Soybean oil production was up 19% in 1970 over 1969, from 5.7 million MT to 6.8 million MT. Also prices were up as much as 46%. On a protein cost/kg basis, soybean are a cheap source of protein. Recent development in the utilization of soybean protein in the form of concentrates, isolates, and textured protein for human consumption offers a solution to the world's protein needs. The highest production yield reported in Agricultural Statistics 1981 for 1979–80 was 6.25 MT/ha for Canada; the lowest 1.54 MT for USSR with the US at 4.00 MT, Mexico at 4.68, Argentina at 5.25 and Colombia at 4.90. Note that these yields are about 21/2 times as high as those reported by Wigham (1981) based on Agricultural Statistics 1977. Correcting the Agricultural Statistics 1981, we get a more realistic 2510 kg/ha for Canada, 1800 for the US, 1870 for Mexico, 2100 for Argentina, 1720 for Brazil, 1960 for Colombia, 1350 for Paraguay, 917 for Romania, 1570 for Yugoslavia and only 616 kg/ha for USSR. Dibb (1983) compares U.S. yields of 1,900 Kg/ha with 1,600 in the developing countries and a reported world record of 7,400 Kg/ha. Wigham suggests 5000–6000 kg/ha as yield with top management and optimum environmental conditions. With only 13 to 25% oil, this suggests a top oil yield of 1500 kg/ha. As of June 15, 1981, soybean oil was $0.21/lb., compared to $0.38 for peanut oil, $1.39 for poppyseed oil, $0.65 for tung oil, $0.33 for linseed oil, $0.275 for coconut oil, $0.265 for cottonseed oil, and $0.232 for corn oil (Chemical Marketing Reporter, June 15, 1981). At $2.00 per gallon, gasoline is roughly $0.25/lb. Pryde and Doty (1981) suggest an average oil yield of only 319 kg/ha from 1,788 kg/ha seed. Telek and Martin (1981) suggest average oil yields of 300 kg/ha.

Energy

In 1979, the low production yield was 150 kg/ha in Tanzania, the international production yield was 1,660 kg/ha, and a world high production yield of 2,525 kg/ha in Egypt. (FAO, 1980a). Comparable yields from Duke (1981a), showing bean:straw ratios of 1700:5000, 3100:7600 and 2800:7100 kg/ha, suggest a straw factor of 2.5, the chaff factor estimated at one. The global average N fixation reported for soybeans is close to 100 kg/ha, about half that of cowpea (Duke, 1981a). Evans & Barber (Science 197: 333. 1977) put the N-fixation figure at 57–94 kg/ha/yr. Maximum growth rate of soybean is 27 g/m2/day for an efficiency of 4.4% (percentage utilization of solar radiation). Maximum growth rate averaged over the usual growth period is considerably lower. With production of 8.9 MT/ha, soybean converts solar energy at an efficiency of only 0.16% (one-tenth that of Napier Grass), if averaged over the whole year (Tropical sugarcane shows an efficiency of 1.0%, cassava 0.8%). (Boardman, 1980). In the tropics, more than one crop per year are possible, and in temperate regions, hot weather soybeans can follow cool weather crops of alfalfa, crambe, peas, or wheat. (Furrow, Mar. 1981). The residue coefficient, defined as the ratio of the weight of dry matter of residue to recorded harvested weight, ranges from 0.55 to 2.60. Soybean residue ratios are often assumed to be representative of other legumes. Upper limits were determined by USDA experts (NAS, 1977a). Schapaugh and Wilcox in 1980 (Crop Science 20:529) studied 24 soybeans and reported harvest indices ranging from 25 to 48%. They define harvest index as seed yield/aboveground biomass. Thus their data show a seed:biomass ratio of 1:4 to 1:2, indicating that we could multiply production figures by 2–4 to convert to biomass data. As of June 15, soybean oil was $0.21/lb., compared to $0.38 for peanut oil, $1.39 for poppyseed oil, $0.65 for tung oil, $0.33 for linseed oil, $0.275 for coconut oil, $0.265 for cottonseed oil, and $0.232 for corn oil (Chemical Marketing Reporter, June 15, 1981). At $2.00 per gallon, gasoline is roughly $0.25/lb. According to the phytomass files (Duke, 1981a), annual productivity for various Glycine spp. ranges from 1 to 20 MT/ha. In North Carolina, where soybeans were the largest crop planted in 1979 and 1980, Harwood (1981) concluded that soybean oil, the most widely available oil in the US, is unlikely to be processed on-farm for oil. "The relatively low oil content (18.5 percent) is more appropriate for large scale solvent extraction than small-scale mechanical processing." Harwood puts the energetic net returns at 2:1 for soybeans, compared to more than 5:1 for sunflower, 3:1 for peanuts, and ca 1:1 for cottonseed. Conversely, studying energy output/input ratios of 11 oilseeds, Goering (1981) found a legume lowest (peanut at 2.2) and highest (soybean at 4.6) among unirrigated crops. Some irrigated crops had ratios of less than 1.0. Of the eleven vegetable oils, soybean oil was lowest in price, available in greatest domestic quantity and had the highest ratio for non-irrigated vegetable oil crops (Goering, 1981). The gross heating value of the oils was 87–89% that of No. 2 diesel fuel (except castor oil, at 82%). Eight parts of soybean oil were emulsified with two parts 190-proof ethanol, using five parts of 1-butanol as emulsifier. The microemulsions performed as well as diesel fuel and were able to start a cold engine (Goering, 1981). At Seminar II (Vegetable Oils as Diesel Fuel; Oct. 21, 22, 1981), soybean oil at $0.20 lb was calculated to cost $1.54 a gallon compared to $1.20–1.35 per gallon for diesel. Comparing soybean oil with No. 2 diesel oil, Freedman and Pryde (1981, VODF Seminar II) note that although density, cetane number, and heat content are of the same order of magnitude, soybean oil is 10 times more viscous and essentially non volatile. In VODF Seminar II, S. J. Clark suggests several reasons why soybean is a viable alternative. (1) it is renewable (2) its production is a well-established technology (3) it fixes its own nitrogen (4) high protein soycake is a byproduct of soy oil production and (5) soy oil esthers have fuel physical properties similar to diesel fuel. In that same symposium (VODF Seminar II), Lipinsky et al. (1981) said "Soybean oil, due to its availability and low cost relative to the other seed oils, is viewed as having the most potential as an emergency diesel fuel substitute in the near term."

Biotic Factors

Insects known to attack soybeans include corn earworms, Mexican bean beetles, bean leaf beetles, velvetbean caterpillars, lesser cornstalk borers, stink bugs, and other insects. Occurrence, prevalence and rate of reproduction of soybean insects vary greatly from one part of the country to another. All insects can be controlled by timely dusting or spraying with the proper insecticide. Local agriculture agents should be consulted for advice. Mexican bean beetles are said to ignore soybeans when snapbeans are planted nearby. The more important fungal diseases of soybeans are: Alternaria sp. (leaf spot), Cephalosporium gregatum (brown stem rot), Colletotrichum truncatum (anthracnose), Cercospora kikuchii (purple seed stain), C. sojina (frogeye leaf spot), Corynespora cassiicola (target spot), Diaporthe phaseolorum var. caulivora (stem canker), D. phaseolorum var. sojae (pod and stem blight), Erysiphe polygoni and Microsphaera diffusa (powdery mildews), Fusarium orthoceras (root rot), Glomerella glycines, Macrophomina phaseoli (charcoal rot), Melanopsichium missouriense (soybean smut), Nematospora coryli (yeast spot), Peronospora manshurica (downy mildew), Phakopsora pachyrhizi (soybean rust), Phyllosticta sojicola (Phyllosticta leaf spot), Phymatotrichum omnivorum (root rot), Phytophthora megasperma (Phytophthora rot), Pythium ultimum and P. debaryanum, Rhizoctonia leguminicola (black patch), R. solani, Sclerotinia sclerotiorum (stem rot), Sclerotium rolfsii (blight), and Septoria glycines (brown spot). Virus diseases include: soybean mosaic, bud blight, and yellow mosaic. Insect vectors are known for all but one of the important soybean viruses, aphids being the most important vector. Types of nematodes attacking soybeans include: sting (Belonolaimus longicaudatus), ring (Criconemoides), spiral (Helicotylenchus), lance (Hoplolaimus), pin (Paratylenchus), root-lesion (Pratylenchus), stubby root (Trichodorus), and stunt (Tylenchorrhynchus). In Taiwan, Thailand, and eastern Australia, soybean rust is soybean's economically most important disease. As the soybean spreads soybean rust becomes increasingly threatening to areas where it is not yet known to occur, (e.g. the US). A direct relation between the amount of carbohydrate exuded by germinating soybeans and seed rot caused by Pythium has been demonstrated. In the US, yield losses of as much as 10% may be due to nematodes, with root-knot nematodes (Meloidogyne spp.) causing 4%, soybean cyst nematodes (Heterodera glycines) 4%, and other nematodes about 2%. As many as 50 species from 20 genera are reported to feed on soybeans. Disease-resistant cvs of soybeans have been developed and are available for production in most production areas. The use of disease-resistant cvs is the most effective means of reducing losses from diseases. Also available are cvs which resist the development of root-knot and cyst nematodes. The use of resistant host plants may be the most desirable and ecologically sound method for managing plant-feeding insect populations. On soybean cvs with normal pubescence high populations of the potato leaf hopper, Empaosca fabae, do not develop. The major insect pests for which resistance has been found include the velvetbean caterpillar (Anticarsia gemmatalis [Hubner]), Mexican bean beetle (Epilachna varivestis [Mulsant]), tobacco budworm (Heliothis virescens [Fabricus]), corn earworm (Heliothis zea [Boddie]), green cloverworm (Plathypena scabra [Fabricus]), and the soybean looper (Pseudoplusia includens [Walker]).

References

Complete list of references for Duke, Handbook of Energy Crops
Last update Wednesday, January 7, 1998 by aw