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Arachis hypogaea L.

Fabaceae
Groundnut, Peanut

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 unpublished.

  1. Uses
  2. Folk Medicine
  3. Chemistry
  4. Toxicity
  5. Description
  6. Germplasm
  7. Distribution
  8. Ecology
  9. Cultivation
  10. Harvesting
  11. Yields and Economics
  12. Energy
  13. Biotic Factors
  14. Chemical Analysis of Biomass Fuels
  15. References

Uses

Seeds yield a non-drying, edible oil, used in cooking, margarines, salads, canning, for deep-frying, for shortening in pastry and bread, and for pharmaceuticals, soaps, cold creams, pomades and lubricants, emulsions for insect control, and fuel for diesel engines. The oil cake, a high-protein livestock feed, may be used for human consumption. Other products include dyes, ice cream, massage oil, paints, and peanut milk. Seeds are eaten raw, whole roasted and salted, or chopped in confectioneries, or ground into peanut butter. Young pods may be consumed as a vegetable. Young leaves and tips are suitable as a cooked green vegetable (Martin and Ruberte, 1975). Javanese use the tips for lablab, and germinating seeds to make toge (Ochse, 1980). Scorched seeds may serve as a coffee substitute. Peanut hulls are used for furfural, fuel, as a filler for fertilizers, and for livestock feed, or sweeping compounds. Foliage provides silage and forage. Hogs may glean the fields following the harvester. Most U.S.A. production enters the peanut butter (50%), salted peanuts (21%), and confectionery (16.5%) markets. Elsewhere peanuts are processed mainly for oil (Duke, 1981a).

Folk Medicine

Duke and Wain (1981) cite folk useage for aphrodisiac, cholecystosis, decoagulant (but see below), inflammation, and nephritis. Peanuts play a small role in various folk pharmacopoeias. In China the nuts are considered demulcent, pectoral, and peptic; the oil aperient and emollient, taken internally in milk for gonorrhea, externally for rheumatism (Duke and Ayensu, 1985). In Zimbabwe the peanut is used in folk remedies for plantar warts. Hemostatic and vasoconstrictor activity are reported (List and Horhammer, 1969–1979). The alcoholic extract is said to affect isolated smooth muscles and frog hearts like acetylcholine. The alcoholic lipoid fraction of the seed is said to prevent hemophiliac tendencies and for the treatment of some blood disorders (mucorrhagia and arthritic hemorrhages) in hemophilia.

Chemistry

Shelled, uncooked, seeds are reported to contain approximately per 100 g: over 500 calories, 4–13 g moisture, 21.0–36.4 g protein, 35.8–54.2 g fat, 6.0–24.9 g total carbohydrate, 1.2–4.3 g fiber, 1.8–3.1 g ash, 49 mg Ca, 409 mg P, 3.8 mg Fe, 15 mg b-carotene equivalent, 0.79 mg thiamine, 0.14 mg riboflavin, 15.5 mg niacin, and 1 mg ascorbic acid. Roasted seeds contain in broad average figures per 100 g: 595 calories, 1.8 g moisture, 23.2 g protein, 50.9 g fat, 21.7 g total carbohydrate, 3.2 g fiber, 2.4 g ash, 42 mg Ca, 354 mg P, 0.45 mg thiamine, 0.11 mg riboflavin, and 15.3 mg niacin. Boiled seeds contain per 100 g: 235 calories, 44.6 g moisture, 16.8 g protein, 8.3 g fat, 26.3 g total carbohydrate, 6.1 g fiber, 4.0 g ash, 45 mg Ca, 260 mg P, 5.1 mg Fe, 0.44 mg thiamine, 0.16 mg riboflavin, and 1.4 mg niacin. Raw leaves contain per 100 g: 69 calories, 78.5 g moisture, 4.4 g protein, 0.6 g fat, 14.9 g total carbohydrate, 4.6 g fiber, 1.6 g ash, 262 mg Ca, 82 mg P, 4.2 mg Fe, 7,735 mg b-carotene equivalent, 0.23 mg thiamine, 0.58 mg riboflavin, 1.6 mg niacin, and 98 mg ascorbic acid. The oilseed cake is said to be a good source of arginine and glutamic acid, used in treating mental deficiencies (Perry, 1980). Hager's Handbook (List and Horhammer, 1969–1979) states that seeds contain 20–30% nitrogenous matter, 2–5% cellulose, 8–21% starch, a-cephalin, xanthine, glutathione, D- and g-tocopherol, arginine, guanosine, chorine, lecithin, saccharose, conglutin, conarachin, L-(-)-cystine, sarkosine, biotin, thiamin, vitamin P, conenzyme A, a-ketoglutaric- and g-methylent-a-ketoglutaric acid, traces of 4-methyleneproline, allantoinase, phospholipase D, isocitratylase, fumarase, etc. Yoshida and Hasegawa (1977) report 2.14 nmol/g atizolamine (1-methyl-3-guanidino-6-hydroxymethylpyrazine-2-one) in the seeds. The testa contains arachidoside, leucocyanadin, and leucodelphinidin. Analyses of the haulms from South Africa showed 9.9% CP, 21.1% CP, 9.3% ash, 2.4% EE, 57.3% NFE, 1.48% Ca, and 0.08% P. The testa (skins from India) contained 12.1% CP, 7.1% CF, 16.7% ash, 46.3% EE, 0.24% Ca, and 0.14% P. Hulls from Nigeria contained 4.9% CP, 68.4% CF, 7.4% ash, 0.6% EE, and 18.7% NFE. The so-called germ, a byproduct of the manufacture of peanut butter contains 3.0% CP, 2.0% CF, 3.0% ash, 46.0% EE, and 46.0% NFE, all these on a zero-moisture basis (Gohl, 1981).

Toxicity

Of greatest concern is possible contamination of damaged or spoiled seeds with the teratogenic, carcinogenic aflatoxins. Two principal toxins, aflatoxins B, and G, and their less toxic dihydro derivatives, aflatoxins B2 and G2 are formed by the aflatoxin producing moulds (Aspergillus flavus et al). Prevention of mould growth is the mainstay, there being no satisfactory way to remove the toxins from feed and foods (however, peanut oils are free of aflatoxins because of alkaline processing). LD50 for aflatoxin for sensitive organisms may be less than 1 mg/kg body weight. "Aflatoxin B1 appears to be the most potent hepatocarcinogen known." Rats receiving only 15 ppm aflatoxin in the diet have high cancer incidence (NAS, 1973). Arachin, with 4 antigens and conarachin with 2 antigens are also reported.

Description

Annual ascending (Guaranian and sequential Peruvian) to somewhat longer-lived ascending, decumbent, or prostrate (Bolivian and Amazonan), geocarpic, glabrate to hirsute herbs with upright main or n-axes. Tap root with four series of spirally arranged lateral roots with abundant branching and usually heavily supplied with nodules. Root tip without epidermis and without root liars. Leaves stipulate, pinnate with two opposite pairs of leaflets, alternately arranged in a 2/5 phyllotaxy on main axis; distichous on higher order branches. Flowers pea-like, enclosed between two bracts, one simple, subtending a very short peduncle, the other bifid, subtending the pedicel; sessile, but appear to be stalked after growth of a tubular hypanthium just before anthesis. The ovary is surrounded by the base of the hypanthium (perigynous), on the distal end of which are inserted two calyx lobes, one awl-like opposite the keel and the other broad and four-notched opposite the back of the standard. Petals, orange, yellow, cream or rarely white; inserted between the calyx lobes and ttle fused bases of the anther filaments (staminal column). The standard is orange with red veins marking the more yellow central face or brick-red by extension of the red veined area. Wings yellow, or yellow at base and orange apically, to brick-red; keel colorless to faintly yellow, clasping the staminal column and bending at right angles with it about halfway along its length. Stamens 10, sterile filaments usually 2, anthers 8 (sometimes 9, rarely 10), 4 globose, uniloculate, alternating with 4 oblong, 3 of which are biloculate and 1, opposite the standard, uniloculate. The tip of the ovary, bearing from 1–5 ovules, grows out from between the floral bracts, bearing with it the dried petals, calyx lobes and hypanthium; creating a unique floral stucture—the peg. The peg quickly turns down toward the soil and thrusts its tip with its ovules several centimeters into the soil where the tip turns horizontally and develops into the pod. Fruit, an indehiscent legume up to 10 cm long; seeds 1–5, from less than 1 cm long x 0.5 cm thick to 3.5 cm x 1.5 cm weighing less than weight less than 0.2 g to over 2.0 g. Testa thin, colors pink, red, purple, tan, brown, yellow, white or red and white, pink and white, brown and white, purple and white, or marked with small purple dashes or splashes on a base color. Flowering under 30 days to over 40 days. Fruit matures 90–150+ days. (2n = 4x = 40). Self-pollinating, occasionally outcrossed by bees (Duke, 1981a).

Germplasm

With 15 to 70 species, the peanut genus has its center of diversity in the Matto Grosso of Brazil. Most species are diploid (2x = 2n = 20). Annual species are more characteristic and tolerant of semiarid areas, perennials of humid high-rainfall areas. Peanuts are quite tolerant of acid soils, and aluminum, requiring a minimum of lime for acceptable yields (Duke, 1982). Over 4,000 entries in the germplasm bank in the United States have arisen from the Guaranian (Spanish, Valencia, Natal Common, Barberton, Manyema, Tatu, Pollachi and numerous other locally named cvs), the Bolivian and Amazonan (Virginia Bunch, Virginia and Georgia Runners, Matevere, Overo, Mani Pintado, etc.) and Peruvian (Tinga Maria, Chinese) gene centers and their extensions into North America, Africa, Europe and Asia. Cultivar distinction within botanical cvs is based on pod and seed. In addition to the cultivated peanut, there are wild Arachis species known to be cross-compatible with cultivated peanuts and known to possess resistance to pests and diseases, including early and late leafspot and spidermites. Cultivars resistant to diseases: 'Schwarz 21', resistant to slime disease, Pseudomonas solanacearum; 'Tarapota' and PI's 314817 and 315608, resistant to rust, Puccinis arachidis; INC 3033', resistant to black rot, Cylindrocladium crotalariae; I.R.H.O. Nos. 56-369 and 'H32', resistant to rosette virus; Valencia PI's 337394F and 337409, resistant to Aspergillus flavus; 'Tarapoto' and PI 109839, resistant to early leafspot, Cercospora arachidicola; NC 2, resistant to stem rot, Sclerotium rolfsii; PI's 295233 and 290606 resistant to lesion nematode, Pratylenchus brachyurus; and 'Natal Common' and 'Kumawu Erect', resistant to root knot nematode, Meloidogyne arenaria. Cultivars resistant to insects: 'Southeastern Runner 56-15', resistant to fall armyworm, Spodoptora frugiperda; 'NC 6', resistant to the southern corn rootworm, Diabroctica undecimpunctata howardi; 'Spancross' to leaf feeding; 'NC 10247', 'NC 102721, INC 15729' and 'NC 157451, resistant to the potato leaf-hopper, Empoasca fabae. Assigned to the South American and African Centers of Diversity, peanut or cvs thereof is reported to exhibit tolerance to aluminum, disease, drought, frost, fungus, high pH, heat, insects, laterite, limestone, low pH, sand, smog, savanna, ultraviolet, and virus (2n = 40) (Duke, 1981a)

Distribution

Native to South America; now widely cultivated in warm countries throughout the world. Introduced in pre-Columbian times to West Indies and Mexico, in early post-Columbian times to Africa and eastern Asia and during the colonial period to Atlantic North America. Known only in cultivation (Duke, 1981a).

Ecology

Suitable for tropics, subtropics and warm temperate regions, grown from 40°S to 40°N latitude. Growing period 3 1/2–5 months ('Chico' matures in 80 days in South Texas). Frost sensitive. Thrives with 5 dm water in the growing season with most in mid-one-third of season. Grows on light, friable, well-drained sandy loams, but will grow in heavier soils. Ranging from Cool Temperate Moist through Tropical Thorn to Wet Forest Life Zones, peanut is reported to tolerate annual precipitation of 3.1 to 41.0 dm (mean of 162 cases 13.8 dm), annual mean temperature of 10.5°C to 28.5°C (mean of 161 cases 23.5°C), and pH of 4.3 to 8.7 (mean of 90 cases = 6.5) (Duke, 1981a).

Cultivation

All commercial peanuts are propagated from seed. Virginia-type (alternately branched) peanuts have a dormancy period; Spanish-Valencia types (sequentially branched) have little or no seed dormancy. Seedbed should be prepared, either on the flat, or widely ridged. Seed often treated with antifungal dressing before planting. In countries of advanced agriculture, peanuts are often grown in monoculture and by mechanized means. In many countries they are cultivated by hand and sometimes in mixed culture. The spacing and seed rate vary with growth rate vary with growth habit and production methods. Stands of 250,000 plants per hectare are sought in machine-drilled planting. For types planted by hand, however, much lower seed rates may be used. Weeds are controlled by cultivation and by pre- and post-planting applications of selective herbicides. Responses to N applied early are common and large in short season cvs in semi-arid regions of West Africa. Phosphorous (P) is added on tropical red earths but less on temperate sandy soils on which other crops in the rotation receive P fertilizer. Roots and fruits absorb nutrients. Calcium (Ca) supply in the pegging zone is essential for high yield of good quality peanuts in large-podded, alternate types. Seeds produced on Ca-deficient soil often have poor germination and poor seedling growth. In tropical red soils of Africa, addition of S may be beneficial (Duke, 1981a).

Harvesting

Although flowering may commence in 30 days, 80–150 days or more are required for fruit maturation. In hand-harvest plants are pulled up and turned over on the ground or stacked or placed on racks to cure. Pods are picked and allowed to complete drying in depths of 5 cm or less on trays, or spread in the sun in the dry season tropics. In case of fully mechanized harvesting a single operation pulls up, inverts and windrows the plants where they remain a few days for preliminary drying. The pods are removed by combine machines and elevated into baskets attached to the combine or blown directly into trailing "drying wagons" which when full may be towed to a drying station where warm or ambient air is forced through the load of peanuts. In Argentina the combines pick and shell the pods in one operation so that the crop is marketed as dried seeds instead of dried pods.

Yields and Economics

Yields have increased remarkably in the United States and other countries since 1951 and now range from 2000 to 6000 kg/ha. Woodruff (1981) notes experimental yields up to 7,000 kg/ha. Yields with poorer conditions and cvs range from 400–1500 kg/ha. Shelling percentage: 75–80% (sequenial types) and 60–80% (alternate types). World production in 1975 from 19,384,000 hectares was 19,117,000 MT (with shell) averaging 986 kg/ha. Asia produced 11,128,000 MT, averaging 866 kg/ha. Africa produced 5,116,000 MT, averaging 743 kg/ha. North America produced 1,936,000 MT, averaging 2,559 kg/ha; South America, 879,000 MT, averaging 1,128 kg/ha; Oceania, 35,000 MT averaging 1,228 kg/ha and Europe, 23,000 MT averaging 2,202 kg/ha. India was the highest production country with 6,600,000 MT; China second with an estimated 2,791,000 MT; U.S. third with 1,750,000 MT; Senegal fourth with 1,130,000 MT and South Africa fifth with 1,100,000 MT. In 1979, the world low production yield was 400 in Mozambique, international production yield 1,016, and the world high production yield was 3,783 in Malaysia (FAO, 1980a). Bogdan (1977) reports DM yields of 4.5, 5.1, 3.9 and 2.8 MT/ha respectively, 87, 94, 101, and 108 days after sowing. These yields could be trebled in those areas of the tropics where three crops could be grown per year.

Energy

Ratnam (1979) found harvest indices ranging from 20–47% in bunch types, 12–31% in semi-spreading types, and 10–22% in spreading types. This suggests that total DM yields may be from 2–10 times higher than conventional seed yields. This DM may be used for fodder or fuel. Woodruff (1981) notes that maximum U.S. yields may be 6500–7000 kg/ha associated with 9–10 MT DM for hay or soil enrichment (or energy production) and 0.3–0.4 MT dry N-fixing roots per hectare. Peanut residues include the total haulm, often calculated from a harvest index of 1:2. The shell is estimated to constitute 35–48% of the total weight of the harvested peanut, the skin (testa) 4% of the seed or "nut" (Wu Leung et al, 1972). However, in India, the husks are considered to represent 20–32% of the weight, averaging 30%. Husks are largely crude fiber (to 60%), lignin and pentosans. Peanut oil is the cheapest and most extensively used vegetable oil in India (CSIR, 1948), and has also been used for fuel and illumination. According to WOI, the calorific value is 549 cals/100 g (five times that of beef). However, if energy is the target, it seems highly improbable that peanut oil yields will ever compare with oil palm yields. Haulms constitute good fodder, silage or green manure (CSIR, 1948). Fodder yields may run 2–7 MT/ha (Bogdan, 1977). In Georgia, peanut oil "is the best emergency fuel." Of its many advantages, availability is most important. One University of Georgia tractor runs on 100% peanut oil, while two University of Georgia busses operate 8 hours a day on a 30% mixture of peanut oil and diesel fuel. Peanut oil can be made on the farm with a sheller, a press, and a little time to let the gum settle to the bottom of the tank. Currently, peanut oil sells for twice the price of diesel. If farmers grew energy peanuts, they could probably produce 150 gallons of oil per acre (ca 9 barrels per hectare) and would have a welcome outlet for peanuts contaminated by aflo toxins (Anon, 1981a). As of June 15, peanut oil was $0.38/lb., compared to $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, $0.232 for corn oil, $0.21 for soybean oil (Chemical Marketing Reporter, June 15, 1981). At $2.00 per gallon, gasoline is roughly $0.25/lb. In North Carolina, Harwood (1981) concluded, "Peanuts are an unlikely candidate for on-farm production of vegetable oil" because they have to be dehulled prior to processing and the hulls might present a disposal problem (why not use them to fuel the dehulling process?). Further, Harwood adds that peanuts should be segregated into edible and low grade nuts to obtain full value from the crop. These processes are performed in large plants and are not amenable to small on-farm production and processing. Furthermore, peanut was relatively more expensive than cottonseed and soybean oi; relative to diesel over a 15 year period, ranging from 2.5–9.5 times as expensive as diesel. But Harwood also states, "In March, 1981, diesel fuel cost farmers $1.26 per gallon, soybean oil cost $1.96 per gallon, cottonseed oil $2.14 per gallon, sunflower oil $2.29 per gallon, and peanut oil $2.89 per gallon."

Biotic Factors

For a rather monotonous listing of major pests and pathogens of peanut, see Duke (1981a). Fungal diseases include: Ascochoyta arachidis (leaf-spot), Aspergillus flavus (yellow mold), A. niger (crown rot), A. pulvarulentus (crown rot), Botrytis cinerea (blight), Cercospora arachidicola (early leafspot), Cercosporidium personatum (late leafspot), C. canescens, Colletotrichum arachidis (anthracnose), C. dematium (anthracnose), C. mangenoti (anthracnose), Diplodia arachidis (collar rot), D. gossypina (collar rot), Dothiorella arachidis (stem disease), Fusarium moniliforme, F. oxysporum, F. roseum, F. solani var. martii, Leptosphaerulina crassiasca (pepper spot and leaf scorch), Macrophomina phaeoli (wilt, root rot, and stem rot), Oidium arachidis (powdery mildew), Pestalotiopsis arachidis (leafspot), Phyllosticta arachidis and Ph. hypogaeae (leafspot), Puccinia arachidis (rust), Pythium debaryanum (pod rot), P. myriotylum (pod rot), P. ultimum, Rhizoctonia solani (root rot), Rhizopus arrhizus, R. oryzae, R. stolonifer, Rhizoctonia solani (all cause seed and preemergence seedling rot), Sclerotinia arachidis, S. minor (root and pod rot), S. sclerotiorum (root and pod rot), Sclerotium rolfsii (stem rot), Verticillium dahliae and V. albo-atrum (wilt and pod rot), Sphaceloma arachidis (scab), Cylindrocladium crotalariae (black rot of roots, pegs and pods), Phomopsis sojae (leaf and stem diseases), Diaporthe sojae, Phomopsiodes arachidis (stem diseases), Chalara elegans (black hull), Phoma arachidicola (web blotch), Cristulariella pyramidalis (zonate leafspot). Some strains of Aspergillus flavus and A. parasiticus, soilborne pathogens, may enter pods and kernels and produce toxic and carcinogenic aflatoxins. Bacterial diseases: Bacterium solanacearum, Phytomonas solanacearum, Xanthomonas solanacearum, Pseudomanas solanacearum, and brown bacterial leafspot. Viruses: abutilon mosaic, alfalfa mosaic, bean chlorotic ringspot, bean mosaic, bean necrosis, bean yellow mosaic, Brazilian tobacco streak, bunchy plant, chlorotic rosette, Euphorbia mosaic, Kromnek disease, leaf curl, marginal chlorosis, mosaic rosette, ringspot and mottle, Arachis virus I, rugose leafcurl, tobacco mosaic, southern sunnhemp mosaic, tomato spotted wilt, turnip mosaic, white clover mosaic and witches' broom, peanut stunt. Bud necrosis (TSWV) is serious disease in India and rosette can be devastating in Africa. Nematodes: Belonolaimus longicaudatus, Meloidogyne arenaria, M. hapla, Pratylenchus brachyurus. Of lesser importance are: Aphasmatylenchus straturratus, Aphelenchoides arachidis, Criconemella spp., Helicotylenchus spp., Hemicycliohora spp., Hoplolaimus spp., Longidorus spp., Meloidogyne javanica, Pratylenchus spp., Radopholus similes, Scutellonema spp., Telotylenchus spp., Trichodorus spp., Tylenchorhynchus spp., and Xiphinema spp. Insects: (1) Soil insects: lesser cornstalk borer, Elasmopalpus lignosellus Zeller; southern corn rootworm, Diabrotica undecimpunctata howardi Barker and also D. balteata; whitefringed beetles, Graphognathus spp.; burrowing bug, Panageaus bilineatus Say and P. congruus; white grub, Strigoderma arbicola Fabricius; bahiagrass borer, Derobrachus brevicollis Audinet-Serville; and wireworms Conoderus, Melanotus, Heteroderes and Cebrio. (2) Foliage insects: corn earworm, Heliothis zea Boddie; tobacco budworm, H. virescens Fabricius; fall armyworm, Spodoptera frugiperda J.E. Smith; beet armyworm, S. exigua Hubner; granulate cutworm, Agrotis subterranea (Fabricius); velvetbean caterpillar, Anticarsia gemmatalis Hubner; rednecked peanutworm, Stegasta bosqueella Chambers; the salt marsh caterpillar, Estigmene acrea; green cloverworm, Platypena scabra Fabricius; cabbage looper, Trichoplusia ni Hubner; tobacco thrips, Frankliniella fusca Hinds; potato leafhopper, Empoasca fabae Harris; threecornered alfalfa hopper, Spissistilus festinus Say; and the arachnid spidermites, Tetranychus urticae, T. cinnabarinus and T. desertorum Koch. (3) Storage insects: Indian meal moth, Plodia interpunctella Hubner; Mediterranean flour moth, Anagasta kuehniella Zeller; almond moth, Cadra cautella Walker (Ephestis); sawtoothed grain beetle, Oryzaephilus surinamensis L.; red flour beetle, Tribolium castaneum Herbst; and the confused flour beetle, T. confusum (duVal). Other insects: Aphis craccivora Koch vector of rosette and other viruses (worldwide), Holotrichia sp., white grubs (India), Amsacta sp. (India), Peridontopyge, Entermes, Anoplocnemis and Halticus (Senegal). Dicotyledonous parasites: Alectra abyssinica, A. senegalensis var. arachidis, A. vogelii, Striga asiatica, S. gesneriodies, S. hermonthica, S. lutea and S. senegalensis. Weeds: Ageratum conyzoides, Cenchrus echinatus, Cynodon dac, tylon, Cyperus rotundus, Digitaria longiflora, Digitaria sanguinalis, Echinochloa colonum, Eleusine indica, Portulaca oleracea, Rottboellia exaltata, Setaria pallidefusca, Sorghum halepense, Tribulus terrestris, and Tridax procumbens

Chemical Analysis of Biomass Fuels

Analysing 62 kinds of biomass for heating value, Jenkins and Ebeling (1985) reported a spread of 18.64 to 17.53 MJ/kg, compared to l3.76 for weathered rice straw to 23.28 MJ/kg for prune pits. On a % DM basis, the hulls contained 73.02% volatiles, 5.89% ash, 21.09% fixed carbon, 45.77% C, 5.46% H, 39.56% O, 1.63% N, 0.12% S, and undetermined residue.

References

Complete list of references for Duke, Handbook of Energy Crops
Last update December 29, 1997