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Triticum aestivum L.

Poaceae
Common wheat, Bread wheat

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 unpublished.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. Chemical Analysis of Biomass Fuels
  14. References

Uses

Common wheat, best known and most widely cultivated of the wheats, is cultivated for the grain, used whole or ground. Fine ground, it is the source of flour for the world's breadmaking. Main use is for flour and bread-stuffs known by various names throughout the world. Grain also is the source of alcoholic beverages, beer, industrial alcohol made into synthetic rubber and explosives. Bran from flour milling also an important livestock feed; germ is valuable addition to feed concentrate. Grain fed to livestock whole or coarsely ground. Starch is used for pastes and sizing textiles. Straw made into mats, carpets, baskets, and used for packing material, cattle bedding, and paper manufacturing. Some wheat is cut for hay. Wheat grown for grain crop is also used for pasture before the stems elongate and as a temporary pasturage; it is nutritious and palatable.

Folk Medicine

According to Hartwell (1967–1971), the seeds are used in folk remedies for cancers, corns, tumors, warts, and whitlow. Reported to be antivinous, bilious, demulcent, discutient, diuretic, emollient, excipient, intoxicant, laxative, useful as a poultice, restorative, sedative, used as a shampoo and vulnerary, common wheat is a folk remedy for burns, cancer, diarrhea, dysentery, ecchymosis, epistaxis, fertility, fever, flux, gravel, hematuria, hemoptysis, hemorrhage, incontinence, leprosy, leucorrhea, menorrhagia, neurasthenia, nightsweat, perspiration, scald, tumor, warts, whitlow, and wounds (Duke and Wain, 1981).

Chemistry

Per 100 g, the grain is reported to contain 326–335 calories, 11.57–14.0 g H2O, 9.4–14.0 g protein, 1.8–2.5 g fat, 69.1–75.4 g total carbohydrate, 1.8–2.3 g fiber, 1.7 g ash, 36–46 mg Ca, 354–400 mg P, 3.0–4.3 mg Fe, 370–435 mg K, 0.43–0.66 mg thiamine, 0.11–0.12 mg riboflavin, and 4.3–5.3 mg niacin. The grain contains allantoin plus uricase; sinapic acid has been isolated from wheat germ. The grain is said to cause poisoning in stock, though no toxic principle has been found. Wheat can absorb toxic concentrations of selenium but "selenium" wheat rarely causes poisoning (Watt and Breyer-Brandwijk, 1962). One kg of grain contains 0.03 mg As2O3; grain also contains Mg, Mn, Zn, Fe, and Cu. Amino acid composition is shown in the Table from the Wealth of India.

Essential amino acids in wheat proteins (after Wealth of India)

Inner
endosperm
(%)
Outer
endosperm
(%)
Bran (%) Germ (%) Whole
wheat
(%)
Arginine 2.92 4.50 7.53 6.20 3.81
Histidine 1.65 1.74 1.68 3.03 1.65
Isoleucine 7.02 6.56 4.50 5.23 6.97
Leucine 9.14 7.98 6.52 7.33 8.27
Lysine 1.92 2.60 3.87 5.44 2.80
Methionine 1.12 1.40 1.09 1.28 1.32
Phenylalanine 3.95 3.43 2.45 2.47 3.68
Threonine 2.56 2.72 2.85 6.28 2.78
Tryptophan 0.93 1.12 1.83 0.90 1.03
Valine 3.65 4.02 4.10 4.20 4.00

Wheat germ oil is rich in tocopherols (vit. E) and essential fatty acids. Sitosterol, ergosterol, and campesterol, phospatidic and glyceroinositophosphatidic acids, phytoglycolipid, serine, etc., are also reported. Wheat contains ca 1% pectin. Wheat bran oil is also high in tocopherols, 68% of which is epsilon-tocopherol. Alpha-tocopherol, which has the highest vit. E activity of the tocopherols, constitutes only 11% of the tocopherols in the bran oil. Much more detail on wheat chemistry can be found in the Wealth of India (C.S.I.R., 1948–1976). Fresh forage contains 30–35% DM, of which (ZMB) 8.6–23.3% is CP, 15.1–21.5% CF, 6.1–11.6% ash, 1.8–3.7% EE, and 40.1–66.0 NFE. Straw, on the other hand, contains 92.0% DM, of which 3.1% is CP, 45.4% CF, 10.2% ash, 1.1% EE, and 40.2% NFE. Indian hay (ZMB) contained 5.1% CP, 35.1% CF, 7.2% ash, 1.3% EE, and 51.3% NFE; Indian silage 3.5% Cp, 39.4% CF, 14.6% ash, 0.5% EE, and 42.0% NFE (Gohl, 1981). Leaf protein isolate contains (g/16g N): methionine, 2.39; tryptophane, 1.41; histidine, 1.97; arginine, 9.16; and total lysine.

Description

Annual grass; culms simple, erect, hollow or pithy, glabrous, up to 1.2 m tall; leaves flat, narrow, 20–38 cm long, about 1.3 cm broad; spikes long, slender, dorsally compressed, somewhat flattened; rachis tough, not separating from spikelet at maturity; spikelets 2–5-flowered, relatively far apart on stem, slightly overlapping, nearly erect, pressed close to rachis; glumes keeled in upper half, firm, glabrous, shorter than the lemmas; lemmas awned or awnless, less than 1.3 cm long; palea as long as the lemma, remaining entire at maturity; caryopsis free-threshing, soft or hard, red or white. Hexaploid.

Germplasm

Reported from the China-Japan, Hindustani, and Central Asia Centers of Diversity, wheat, or cvs thereof, is reported to tolerate alkali, bunt, disease, drought, herbicide, hydrogen flouride, high pH, laterite, low pH, mildew, salt, nematodes, phage, rust, smog, smut, and virus (Duke, 1978). This species is the source of most US wheat cvs, there being >200 named cvs cultivated in the United States. Many other cvs exist elsewhere. Since so many cvs are available, one should consult the agricultural agent of a particular region to ascertain which ones are best for, that particular area. No attempt will be made here to describe these cvs, except to indicate they are classified in the following manner: Hard red spring wheats yielding high quality bread flour; Hard red winter wheats producing superior bread flours; Soft red winter wheats yielding flour for cakes and biscuits; Durum wheat hybrids yielding hard kernels made into semolina for macaroni products; red durum hybrids used in mixed wheat flours; white wheats yielding grain for breakfast foods, flour for cakes, pastries, and crackers, and various mixed wheats used mostly for feeds for livestock. The spring and winter types constitute about 95% of the wheat grown in the United States. (2n = 42.)

Distribution

T. aestivum known only under cultivation; its nativity has been lost. Briggle (1981) states, "The precise origin of the wheat plant as we know it today is not known. Wheat evolved from wild grasses, probably somewhere in the Near East. A very likely place of origin is the area known in early historical times as the Fertile Crescent—a region with rich soils in the upper reaches of the Tigris-Euphrates drainage basin.

Ecology

Ranging from Boreal Moist to Rain through Tropical Very Dry to Dry Forest Life Zones, wheat is reported to tolerate annual precipitation of 1.9 to 25.0 dm (mean of 162 cases = 7.9), annual temperature of 4.9 to 27.8°C (mean of 162 cases = 13.4), and pH of 4.5 to 8.3 (mean of 141 cases = 6.5) (Duke, 1978). Adapted to a wide variety of climatic conditions. Principal wheat-growing areas of the world have similar growing conditions: the Russian prairies, the fertile pampas of Argentina, the Wheat belt of United States, all have fertile dark soils rich in nitrogen; rather hot, cloudless summers; rainfall which, although low, is well-distributed. A good wheat soil has physical structure which holds together, making good water retention and favorable conditions for nitrate formation. Hot, humid conditions are unfavorable for wheat-growing.

Cultivation

Propagation by seeds. Use minimum number of tillage operations to help prevent soil compaction and restriction of root and water penetration. The two principal purposes for preparing a seedbed are the development of nitrates and the conservation of moisture. In areas where rainfall is limited, as in western Kansas, summer fallowing is the most successful method for storing and conserving soil moisture. Good summer fallow is one in which the soil is kept free of plant growth and the soil surface is kept open to permit rapid penetration of moisture, and cloddy to prevent wind and water erosion. Avoid excessive turning up of new soil because such tillage dries out the soil. Start first tillage in spring as soon as weeds begin to grow, usually about May 1. After the first tillage, cultivate soil only enough to prevent weed growth and to maintain a rough surface. In some areas stubble mulch tillage method of fallowing is practiced, by which enough residue is anchored to soil surface to protect the crop and soil from wind and water erosion. Contour and stripe planting may be used. Cultivation of soil well in advance of seeding hastens the decay of organic matter, thus liberating nitrogen and making it available to plants as nitrates. Early seedbed preparation is necessary for highest yields. Crop rotation of fallow, wheat, and sorghum is an excellent practice in some areas. Date of planting wheat seed depends on the locality, type of wheat, and the hessian fly problem. Rates of seeding differ with the type of wheat, size of seed, and locality, varying from 22–100 kg/ha, generally 33 kg/ha is recommended. Local agents should be consulted about weed control. Irrigated wheat averages 86.25 bu/ha instead of 65.5 bu/ha. Wheat uses about 60 cm of water throughout the growing season. The type of fertilizer used should be determined by a soil test. The three main types being nitrogen, phosphorus, and potash. However, moisture, rather than plant food nutrients, is the limiting factor in production in most seasons under dryland farming. Yield response to nitrogen fertilizer is determined by moisture, soil, type of seedbed, and crop stand. Nitrogen may be supplied with anhydrous ammonia, nitrogen solution, or in dry forms as ammonium nitrate, urea or in mixed fertilizers. Phosphate is best supplied with superphosphate or in a mixed fertilizer. Potassium is best supplied with muriate of potash or in a mixed fertilizer. Nitrogen fertilizer and potash may be broadcast and worked into the seedbed before seeding or applied at time of seeding by using a combination fertilizer-grain drill, or applied as a top-dressing during the winter just prior to spring growth. Superphosphates are usually placed in the row with the seed (Reed, 1976).

Harvesting

Winter wheat is most widely used for temporary pasture crop. It can be grazed without apparent injury to the grain crop, provided it is not grazed severely over an extended period of time, or too late in the spring. Pasturing should not begin in fall until plants have become firmly rooted. Grazing should be discontinued just before plants begin to grow erect in preparation for jointing. Harvesting the grain should be delayed until the wheat is sufficiently mature to store well, with moisture content of 13.5% or less under ordinary conditions. Wheat is harvested with combine properly adjusted to minimize grain losses. Storage bins should be cleaned and treated before grain is placed in them. Seed storage to 3 years in dry storage bins.

Yields and Economics

In general, yields of wheat vary from 40.4 to 65.1 bu/ha, with higher yields up to 85 bu/ha obtained with irrigation. Yields depend on climatic conditions, variety or cultivar of wheat planted, size of kernel, and number of kernels per head. Production figures presented by Briggle (1981) showed Iran rather low with 1,100 kg/ha ranging to West Germany with 4,110 kg/ha, cf the US with 2,040 kg/ha. In the US, Ohio was high with 3,162 kg/ha compared with South Dakota at 1,608 kg/ha. In 1979 the world low production yield figure was 160 kg/ha in Jordan, the international production was 1,782 kg/ha, and the world high production yield was 7,000 in U.A.E. (FAO, 1980a). Dibb (1983) compares US yields of 2,100 kg/ha to 1,300 kg/ha in the developing countries and a world reported record of 14,500 kg/ha. Wheat is one of the most important food plants of man. It enters into international trade more than any other food. World production in 1971 was 303 million metric tons. Major producers are, in order, United States, USSR, China, Canada, France, Italy, Indian Union, Argentina, Australia, and Pakistan. The economic stability of many nations is affected by the exchange in wheat and other commodities (Reed, 1976).

Energy

According to the phytomass files (Duke, 1981b), annual productivity ranges from 4 to 18 MT/ha. Chaff is estimated to constitute 25% of the grain. Wheat straw is calculated at 1/2–2 times grain yield, more frequently, 1 1/2 times. However, in some countries, wheat biomass averages more than 6 MT/ha, double this if double cropped. The highest phytomass figure to date in our files is 18 MT/ha/yr. Australians figure that methanol produced from wheat stubble is about 7 times as expensive per GJ as Kuwaite oil, but half as expensive as ethanol from wheat grain ($A 1.25 per GJ for oil, 8.8 for methanol from stubble, 14.1–15.4 for ethanol from grain) (Boardman, 1980). Research reiterated by Palz and Chartier (1980) indicated that straw from winter wheat, summer wheat, winter barley, summer barley, winter rye, and oats all gave calorific values based on moisture-free dry matter of 17.04 (± 5%) MJ/kg, or based on air dry matter 15.06 (± 3.5%) MJ/kg. High N fertilization raised calorific values by ca 425 KJ/kg. Increasing moisture content from 14 to 20% reduced calorific value by 9%. Since straw available as feedstock is normally air-dry, a calorific value of 15 MJ/kg is assumed by Palz and Chartier (1980) for all cereal varieties and species. The assumed grain straw ratio for:
wheat is 1.23
barley is 1.45
oats is 1.16
rye is 0.70
other cereals are 1.10
Elsewhere Palz and Chartier assume 17.5 MJ/kg as the typical energy value for the dry matter of herbaceous materials. Reducing Kvech's (1979) numbers by 10% to convert approximately to DM yields for residues, we have the following figures for Kourim, Czechoslovakia, rounded to the nearest MT: Medicago sativa, 7; Trifolium pratense, 4; Vicia faba, 4; Avena sativa, 3; Lolium perenne, 3; Secale cereale, 3; Trifolium repens, 3; Triticum aestivum, 3; Brassica Tapa, 2; Hordeum vulgare, 2; Phacelia tanacelifolia, 2; Beta vulgaris, 1; Sinapis alba, 1; Solanum tuberosum, 1. The harvest index of cereals in general is ca 0.36, meaning that 64% of total above ground crop production is residue, at least 1/3 of which should be left in the field. 'Prior' barley has the HI ranging from 0.48 to 0.41 with increasing N fertilizer levels. Wheat usually runs about 0.30 to 0.35 HI. Rice often has a high HI, while grain sorghum generally has a low HI. The 'Green Revolution' cereals with short straw and high grain yields have relatively high HI. Biomass engineers might prefer a low HI. The estimated cost of ethanol and methanol from cereal grains is $0.35 per liter, and $0.16 per liter; the overall energy efficiency, i.e. the ratio of the energy value of the gross liquid fuel output to the total energy inputs including feedstocks is 0.34 for ethanol and 0.40 for methanol. For each ton of ethanol produced from cereal grains, there is another ton of dry distiller's residue, valued in the U.S. as animal feed (Stewart et al. 1979). Briggle's figures show that fertilizer constitutes the biggest energy input for spring wheat, 2,102,000 Btu/ha out of a total energy input of 5,646,000 Btu/ha, compared with 3,401,000 out of 7,478 for winterwheat. Preplanting required 1,025,000 Btu/ha for spring wheat, 994,000 for winterwheat; planting takes 268,000–235,000, fertilizer application 10,000–57,000, pesticide application 18,000–44,000, pesticides 14,000–60,000, irrigation 146,000–953,000, harvesting 257,000–398,000, truck 271,000–368,000, grain handling 7,000–15,000, farm pickup 763,000–800,000, farm auto 220,000–233,000, electricity and overhead, 42,000, miscellaneous 54,000 to 326,000 Btu/ha (Briggle, 1981). Briggle's earlier work (1980) showed wide variation in output/input ratios, the highest ratio (4.64) representing hard red spring wheat yields of ca 4.7 MT/ha (equiv. 15,500,000 kcal/ha) from energy inputs of only 3,350,000 kcal/ha in Idaho, the lowest ratio being 0.43, representing Texan winter wheat yields of ca 2.4 MT/ha. Energy inputs ranged from 2–18 million kcal/ha and yields from ca 1,000 to 5,000 kg. Briggle (1980) adds that wheat is an energy frugal crop, produced with the energy equivalent of less than 5 barrels oil/ha compared to corn at closer to 10 barrels and potatoes at nearly 25.

Biotic Factors

Wheats are attacked by many fungi and other organisms. Some cvs are resistant to the various rusts, smuts, and virus diseases. The most important fungal diseases of wheats are the following. Extension agents should be consulted concerning diseases in an area before growing wheat. Also cvs should be selected for growing which are resistant to such diseases. Fungal diseases of wheat: Rusts (Stem or Black rust, Puccinia graiminis f. sp. tritici; Leaf or Brown rust, P. recondita; Stripe or Yellow rust, P. glumarum); Smuts (Bunt or Covered smut, Tilletia caries and T. foetida; Dwarf Loose smut, Ustilago tritici); Mildews (Downy mildew, Sclerospora macrospora; Powdery mildew, Erysiphe graminis f. sp. tritici); Root rots (Common root rot, Helminthosporium spp. and Fusarium spp.; Take-all root rot, Ophiobolus graminis; Browning root rot, Pythium spp.); Foot rots (Eye spot, Cercosporella herpotrichoides; Snow mold, Fusarium spp.); Blights and Scabs (Head blight or scab, Fusarium spp.; Rhizoctonia blight, Rhizoctonia spp.; Typhula blight, Typhula spp.; Anthracose, Colletotrichum graminicola; Kernel smudge, Helminthosporium spp., Alternaria spp.); Blotches (Glume blotch, Septoria nodorum; Leaf blotch, S. tritici; Speckled leaf disease, Leptosphaeria avenaria f. sp. triticea; Ergot, Claviceps purpurea. Diseases caused by bacteria include the following: Pseudomonas atrofaciens (Basal glume rot or bacterial black-tip) and Xanthomonas transluscens f. sp. undulosa (Black shaff). Diseases caused by viruses include the following: Wheat mosaic, Wheat streak mosaic, Wheat striate mosaic, and Yellow dwarf. Insect pests encountered in various areas include: English grain aphid is the most common aphid affecting wheat, attacking the heads and being very damaging when populations become high prior to the late-dough stage. Other insects and cutworms, darkling beetles, hessian fly, and salt marsh caterpillars, may cause damage during the seedling stage. A great number of species of nematodes have been isolated from wheats in various parts of the world. Where nematodes are a problem, the agricultural agent should be consulted.

Chemical Analysis of Biomass Fuels

Analysing 62 kinds of biomass for heating value, Jenkins and Ebeling (1985) reported a spread of 17.51 to 16.49 MJ/kg, compared to 13.76 for weathered rice straw to 23.28 MJ/kg for prune pits. On a % DM basis, the straw contained 71.30% volatiles, 8.90% ash, 19.80% fixed carbon, 43.20% C, 5.00% H, 39.40% O, 0.61% N, 0.11% S, 0.28% Cl, and undetermined residue.

Analysing 62 kinds of biomass for heating value, Jenkins and Ebeling (1985) reported a spread of 16.20 to 15.16 MJ/kg, compared to 13.76 for weathered rice straw to 23.28 MJ/kg for prune pits. On a % DM basis, the dust contained 69.85% volatiles, 13.68% ash, 16.47% fixed carbon, 41.38% C, 5.10% H, 35.19% O, 3.04% N, 0.19% S, and undetermined residue.

References

Complete list of references for Duke, Handbook of Energy Crops
Last update Friday, January 9, 1998 by aw