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Sorghum bicolor (L.) Moench

Poaceae
Sorghum, Milo, Broomcorn, Durra, Karrir-corn, Guinea-corn, Shattercane

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 unpublished.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. References

Uses

Though sorghum is used largely for forage in the US, it is very important in the world's human diet, with over 300 million people dependent on it (Bukantis, 1980). Grown for grain, forage, syrup and sugar, and industrial uses of stems and fibers. Grain sorghum is a staple cereal in hot dry tropics, the threshed grain ground into a wholesome flour. Stalks used as animal feed. Important summer fodder where temperatures are high and rainfall insufficient for corn. Most important for silage or green soiling, or for hay when grown irrigated in very dry areas. Pearled grain cooked like rice or ground into flour. Sorghum, with large juicy stems containing as much as 10% sucrose, used in manufacture of syrup; sugar can be manufactured from sorghum. Broomcorn used for making brooms. The seed is used as food, in brewing "kiffir beer", the kiffir corn malt and cornmeal is fermented to make Leting (a sour mash), the pith is eaten, and the sweet culm chewed (Watt and Breyer-Brandwijk, 1962). Arubans make porridge and muffins from sorghum meal. Parched seed are used as coffee substitutes or adulterants (Morton, 1981).

Folk Medicine

Reported to be antiabortive, cyanogenetic, demulcent, diuretic, emollient, intoxicant, and poison, sorghum is a folk remedy for cancer, epilepsy, flux, and stomachache (Duke and Wain, 1981). The root is used for malaria in southern Rhodesia; the seed has been used for breast disease and diarrhea; the stem for tubercular swellings. In India, the plant is considered anthelminthic and insecticidal, and in South Africa, in combination with Erigeron canadense L., it is used for eczema (Watt and Breyer-Brandwijk, 1962). In China, where the seeds are used to make alcohol, the seed husk is braised in brown sugar with a little water and applied to the chest of measles patients. The stomachic seeds are considered beneficial in fluxes (Perry, 1980). According to Morton (1981) Curacao natives drink the leaf decoction for measles, grinding the seeds with those of the calabash tree (Cresentia) for lung ailments. Venezuelans toast and pulverize the seeds for diarrhea. Brazilians decoct the seed for bronchitis, cough and other chest ailments, possibly using the ash for goiter. Arubans poultice hot oil packs of the seeds on the back of those suffering pulmonary congestion. According to Grieve's Herbal (1931), a decoction of ca 50 g seed to a liter of water is boiled down to ca 1/2 liter as a folk medication for kidney and urinary complaints.

Chemistry

Per 100 g, the seed is reported to contain 342 calories, 12.0 g H2O, 10.0 g protein, 3.7 g fat, 72.7 g total carbohydrate, 2.2 g fiber, 1.5 g ash, 22 mg Ca, 242 mg P, 3.8 mg Fe, 8 mg Na, 44 mg K, 0 mg b-carotene equivalent, 0.33 mg thiamine, 0.18 mg riboflavin, 3.90 mg niacin, and 0 mg ascorbic acid (Wu Leung et al, 1972). Seeds contain butyric-, formic-, myristic-, palmitic-, and stearic-acids, maltose, emulsine, and are rather rich in vitamin B (Perry, 1980). Cultivars with highly pigmented seeds are rich in condensed catechin tannin and other phenols (anthocyanins); these are usually the darker bird-, insect-, and/or fungus-resistant cvs. (Morton, 1981). Protein contains no gluten and flour does not make good bread unless mixed with other cereals. Based on 1046 analyses, Miller (1958) reported that the DM ranges from 71.0–96.3%, averaging 89.0%. On a zero-moisture basis, CP ranges from 8.7–16.8% (mean of 1160 cases, 12.5%), EE from 1.4–6.1 (mean of 1159, 3.4%), CF from 0.4–13.4 (mean of 1085 cases, 2.7%), ash from 1.2–7.1% (mean of 1133, 2.2%), and 65.3–85.3% NFE (mean 79.2%); Ca from 0.01–0.53% (mean of 227 cases, 0.05%), P from 0.10–0.52% (mean of 235 cases, 0.35%), Cu 2–19 ppm (mean of 38 cases = 11), K from 0.28–0.50% (mean of 16 cases, 0.38%), Mg from 0.02–0.25% (mean of 23 cases = 0.19), Fe from 0.000–0.018% (mean of 44 cases = 0.005%), and Mn from 0–27 ppm (mean of 42 cases 16 ppm), S from 0.15–0.21% (mean of 6 = 0.18%), Na from 0.01–0.09% (mean of 9 = 0.05%), Cl from 0.07–0.14 (mean of 7 cases = 0.10%), Co from 0.04–0.73 ppm (mean of 22 cases = 0.3), Zn from 12–19 ppm (mean of 2 = 15), 1.3–8.8 ppm thiamin (mean of 50 cases = 4.6), 0.4–5.7 ppm riboflavin (mean of 168 cases = 1.5), 3.3–24.2 ppm pantothenic acid (mean of 165 = 125), 19.4–92.6 ppm niacin (mean of 171 cases = 48.4), 2.2–10.3 ppm pyridoxine (mean of 46 = 5.9), 528–953 ppm chorine (mean of 13 = 761), and 0.2–5.1 ppm carotene (mean of 66 cases = 1.3). Palmer and Bowden (1975) report more than 20 4-demethylsterols, 4-monomethylsterols, and triterpenes. Of 254 analyses of dry roughage, DM ranged from 62.8–94.3% (mean 85.5%). On a zero moisture basis, the dry roughage contained 3.0–17.9% CP (mean of 256 = 7.9), 1.4–3.8% EE (mean of 256 = 2.5), 17.3–38.1% CF (mean of 256 = 26.1), 4.6–18.6% ash (mean of 546 = 8.5%), and 41.0–67.8% NFE (mean 55.0), 0.2–0.8% K (mean of 14 = 1.41%), 0.21–0.4% Mg (mean of 15 = 0.3%), 0.005% Fe, 40–150 ppm Mn (mean of 8115), 0.51–0.74% Cl (mean of 3 = 0.63). One Egyptian variety yields a red dye stuff containing durastantalin (C16H12O5), quercemetrin, a flavanol, and a crystalline substance resembling pyrocatechol has been isolated from the grain (Watt and Breyer-Brandwijk, 1962). Plants yield 27.8% pentosan, valued in furfural manufacture. Culms may contain 3 ppm ascorbic acid.

Toxicity

Sorghum contains hydrocyanic acid and the alkaloid hordenine. Sometimes plants accumulate toxic levels of nitrate (Morton, 1981). Varieties differ considerably in HCN poisonings. Danger is slight when grain is nearly mature. Young plants and suckers are dangerous, particularly when suffering from drought. HCN is destroyed when fodder is ensiled or cured as hay. Varieties vary in recovery with rotational grazing or frequent moving, as well as in quality and in HCN content. Kaffir-corn grain is edible, but the plant is toxic to stock, especially when wilted, due to HCN (52–3,000 ppm) and the cyanogenic glucoside durrin (C14H17O7N). In India the intoxication is known as jowar poisoning. Plants may contain 0.07% of the alkaloid hordenine.

Description

Summer annual, coarse, erect with much variability in growth characteristics; culms solid or sometimes with spaces in pith, 0.6–5 m tall, depending on variety and growing conditions, 5 to over 30 mm in diameter, either dry at maturity or with sweet insipid juice; leaves broad and coarse, similar in shape to those of corn but shorter and wider; blades glabrous and waxy; sheaths encircle culm and have overlapping margins; panicle erect, sometimes recurved, usually compact in most grain sorghums and more open in forage types; seed covered by glumes that may or may not be removed by threshing; prop roots may grow from culm nodes; bud at each node from which a tiller may grow; seeds white, yellow, red, or brown; panicle with up to 6,000 spikelets. Seeds 25,000 to 61,740/kg; grass sorghum 120,000 to 159,000/kg.

Germplasm

Reported from the China-Japan, Hindustani and Mediteranean Centers of Diversity, sorghum, or cvs thereof, is reported to tolerate alkali, anthracnose, disease, drought, fungus, herbicide, high pH, heat, insects, laterite, low pH, mildew, poor soil, rust, salt, savanna, virus, weeds, and waterlogging (Duke, 1978). An important warm-season annual, developed by crossing cytoplasmic male-sterile sorghum lines with improved cvs of sudangrass. Numerous cvs have been developed including grain sorghums, sweet sorghums, and broomcorns, some of which have been referred to various different species and subspecies. `NB-280S', developed in Nebraska, has good seedling vigor and rapid regrowth vigor, stem size and leaf width larger than in true sudangrass but less than in some sorghum x sudan hybrids, low HCN at pasture stage, yields equal to or better than standard sudangrass varieties, lodging may be a problem if crop is grown for silage. 'Suhi 1', developed in Georgia, has wide leaves, rather dry stems, and good seedling vigor, rapid regrowth up to 4 m when allowed to mature, adapted to most areas where sudangrass is grown, good disease resistance; at maturity dark seeds have reddish-brown to black glumes; because of high HCN potential, should be grazed with caution. Many other cvs developed especially for climatic and use conditions. As Duke (1982a) reports, this was the most dramatic case in which his data base (Duke, 1978) was used to select germplasm for a marginal environment. Skepticism of reported high pH in Duke's table prompted inquiries. The computer selected, in answer to the skepticism, 14 reports of sorghum at pH > 7.5. Inquiries to 10 of these produced 4 lots of seeds, two iron-efficient, which would grow well at pH > 8.0. (2n = 20)

Distribution

Main center of distribution of cultivated sorghums is in Africa, having been cultivated in Ethiopia for more than 5,000 years; possibly cultivated sorghums were also developed independently in India and China. Forage sorghums introduced in United States about 1850. Now sorghums are widely distributed throughout tropics, subtropics, and warm temperate areas of the world.

Ecology

Ranging from Cool Temperate Steppe to Wet through Tropical Thorn to Wet Forest Life Zones, sorghum is reported to tolerate annual precipitation of 2.0 to 41.0 (mean of 86 cases = 10.9), annual temperature of 7.8 to 27.8°C (mean of 86 cases = 20.1), and pH of 4.3 to 8.7 (mean of 69 cases = 6.7). Adapted to tropical and subtropical summer rainfall climate with rainfall from 25–125 cm annually; of little importance in more humid areas with higher rainfall. Some cvs are short-day plants. Adapted to wide range of soils varying from light loams to heavy clays; thrives best on light, easily worked soils of high fertility, with moderate to high available water, with erosion not a problem. Moderately well-drained soils are suitable for sorghums. Small amounts of alkali in sand reduces performance considerably. Tolerance to salinity is moderate. Prefers moderately acid soil; pH down to 5.7 does not drastically affect production.

Cultivation

In dry-land conditions, seed normally sown in rows 75–100 cm apart at rate of 3–9 kg/ha; higher seed rates used for more humid areas. In good rainfall or under irrigation, seed should be close drilled or broadcast at rate of 20–35 kg/ha, this resulting in more leaf and less heavy stems, also obviating weeding. Seeds germinate best between 20–30°C, with poorer germination higher or lower. Seeded in rows like corn in most areas. Seeding may be as early as March, as in southern Texas; but date of planting depends on use for which crop is intended. In tropics, sorghums may be planted nearly anytime. Crop sown on well-prepared, firm, moist seedbed. Seed planted to depth of 1.5–5 cm depending on soil texture and moisture. Compact soil if dry! Seeding before soil temperature at 10 cm reaches 12–13°C can be injurious. Later or multiple plantings are often made to equalize forage production throughout the season. In subtropical climates, seeding in late summer or early fall may also be made. Sorghum hybrids are rather sensitive to low pH and low P and K availability. Generally fertilizer with 30–60 kg/ha P and 60–120 kg/ha K is used. Good responses of N fertilizer up to 200 kg/ha have been obtained. Rotational or strip grazing is practiced. Non-tillering cvs are usually spaced 10–14 cm apart in rows, whereas profuse tillering varieties are spaced 30–45 cm apart. Weed control by chemicals or mechanical means important as crop grows slowly in early stages. Cultivate or harrow once after plant emergence and later as required; usually 1–3 cultivations necessary in tropics. Shallow cultivation essential to prevent damage to surface roots. Constant roguing necessary of off-type plants before flowering for both open pollinated and hybrid seed production. (Reed, 1976)

Harvesting

Greatest dry matter yields are obtained at maturity, or when stems are 80–120 cm tall, such heights are suitable for hay, silage, and green chop; best grazed at 20–30 cm height; best regrowth when 10–15 cm stubble left. Some sorghum cvs are very productive, yielding more DM than corn. Cut when grain is in dough stage, and feeding value of fodder is at maximum. Harvesting for green chop or silage is well-suited to mechanical harvesting due to bulk and mass involved. Sorghum for silage should be harvested when seeds are in milk to dough stage. When used for hay, 2–5 harvests may be made per season, each with a potential yield of 2MT/ha or more. Hay is difficult to cure because of the thick culms, requiring several days in sunshine. A forage crusher helps reduce the time. Pasturing is cheapest method of harvesting forage. For seed, crop is cut by hand or mower, smaller dwarf types combined. If cut by hand, heads dried in heaps on ground or on threshing floor. If entire plant is cut by hand or binder, it should be stooked and left in field to dry and mature for 10–14 days, and then threshed. Seed stored at 12–13% moisture or less. Freshly harvested seed may show dormancy. Hard textured seed may be scarified to improve germination.

Yields and Economics

Seed yields may be as low as 200 kg/ha, or as high as 6,000 kg/ha, depending on cv and growing conditions; below 2,000 kg/ha considered not profitable. Average forage yields for silage; Sorgo, 'Start', 54.3 MT/ha; 'Honey', 48 MT/Iha; 'Atlas', 42 MT/ha; Sorgo hybrids, 43.4–71.4 MT/ha. (Reed, 1976) Sorghum is the fourth most important world cereal grain, following wheat, rice, and corn. Worldwide, grain sorghum is grown on more than 40 million hectares, especially in China, India, and Africa. Grain sorghum hybrids are becoming increasingly available to American farmers as the result of discovery of cytoplasmic male sterility in 1952. There is 30–30% efficiency in production. About 7.3 mil. ha of sorghums grown in US, about 25% grown for forage and 75% for grain and seed. It is most important in the Great Plains and southern US for silage, pasture, and soilage. Dibb (1983) compares US yields of 3,300 kg/ha with 900 kg/ha in the developing countries and a reported world record of 21,500 kg/ha. In 1979 the world low production yield figure was 260 kg/ha grain in Botswana, the international production yield, 1,322 kg/ha, and the high, 5,326 kg/ha in Spain (FAO, 1980a). Logsdon (1974) states that a good sorghum acre will produce 400 gallons of syrup (ca 25 barrels/ha). At $3 to $4 per gallon, this makes a nice sideline income for the small farmer.

Energy

Sorghums are high on the priority list of energy crops. The genus Sorghum includes grain sorghums noted for their ability to grow in dry climates and to manufacture starch efficiently. Sweet sorghums noted for their high yields of directly fermentable stalk sugars and their ability to grow anywhere that corn or soybeans grow, and sweet-stemmed grain sorghums which are crosses of grain sorghum with sweet sorghum and which combine the characteristics of the two types. Sorghum-based ethanol has a favorable energy input-output ratio. Because the stalk residues can be used for fuel and sorghums require less fertilizer than does corn. The directly fermentable sugars in the stalk present a challenge in that they are unstable compared with starch. Whether sweet sorghum and sweet-stemmed grain sorghum can become viable energy crops will depend on solving this serious seasonality problem. Processing facilities must be large enough to handle the entire crop in a matter of weeks, and the conversion to ethanol or other energy products must be spread out over a sufficient time period to keep unit capital investment low. Integrated systems are under development to solve the seasonality problem, e.g., (1) integration of sorghum crops with sugarcane agriculture in the south and of corn agriculture in the north, (2) integrated processing and conversion of the stalk sugars and grain from sorghum or other crops, (3) ethanol production from sorghum's simple carbohydrates and from its lignocellulose (Lipinsky and Kresovich, 1980). The harvest index (HI) 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. The estimated cost of ethanol and reethanol 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 impute including feedstocks is 0.34 for ethanol and 0.40 for reethanol. For each ton of ethanol produced from cereal grains, there is another ton of dry distiller's residue, valued in the US as animal feed (Stewart et al, 1979). DM yields of 13–15 MT are reported in one Brazilian study, 14–17 in a US study, 24–28 MT in Iraq (just stalks) (Gill et al, 1977), 2.5–15 in Oklahoma (Denman, 1975), 12 MT in Cuba (Menendez and Martinez, 1980), 6–8 in India (Itnal et al., 1980), 14–33 in Louisiana (Ricaud et al., 1981). Sorghum, at 32 MT/ha stem and 3 MT grain, will give 3 to 4,000 liters alcohol per ha (Coombs and Vlitos, 1978). K.C. Freeman estimates 1250–2000 gallons per hectare (Ag. Research, July 1981). The grain itself could be sold for uses other than alcohol production because it provides only ca 5% of alcohol production (i.e. in sweet sorghum). Sugars in the stalks provide about 80% of the alcohol and those in stalk fibers about 15%. In Louisiana, Ricaud et al. (1981) reported 1070 to 1635 gallons per hectare, equalling ca 25–40 barrels ethanol per ha. According to Bukantis (1980), the energy output:input ratio for grain sorghum is ca 4:1 in non-irrigated fields in Kansas, ca 1:1 in irrigated fields, 4.5:1 in rainfed fields in Nebraska, 3–5:1 in irrigated fields, 3:1 in rainfed fields in Texas, 1.5:1 in irrigated fields of Texas, 37:1 in manual-labor fields in Sudan but only 1:1 in draft-animal production in Nigeria (I suspect they calculate feed for the oxen but no food for the man to make the big difference here). According to Pal and Malik (1981) Azospirillum brasilense contributed 5.8–19.6 kg N/ha to N uptake of cv CSH-5. Grain yields were 1,167 kg/ha without fertilizer, 1,780 kg/ha with inoculation with Azospirillum, 2,048 kg/ha with 10 tons FYM, and 2,435 kg/ha with FYM and inoculation. The straw factor is calculated at 1, the chaff factor at 0.25. Forage sorghum is a promising energy source. Forage sorghum in the 120-day growing season of California showed a mean growth rate of 23 g/m2/day for production of 27.6 MT/ha; in an 83-day growing season in Australia, the growth rate was 17 g/m2/day, for total production of 14.1 MT/ha (Boardman, 1980).

Biotic Factors

Major diseases reported on sorghums include the following: Cercospora sorghi, Colletotrichum graminicola (Anthracnose of leaves and stems), Helminthosporium turcicum (leaf blight), Macrophomina phaseoli (charcoal rot), Periconia circinata (milo disease), Phyllachora sorghi, Phyllosticta sorghi, Puccinis purpurea (rust), Ramulispora sorghi (sooty strip), Sclerospora sorghi (downy mildew), Sorosporium ehrenbergii, Sphacelia sorghi, Sphacelotheca sorghi (coverd smut), Sph. cruenta (loose smut), Sph. reiliana (head smut). Plants are also severely attacked by various species of Striga (S. lutea, S. hermontheca, S. senegalensis, S. densiflora). Nematodes isolated from sorghum include the following species: Helicotylenchus cavenessi, H. dihystera, H. pseudorobustus, Hoplolaimus pararobustus, Meloidogyne javanica, Peltamigratus nigeriensis, Pratylenchus brachyurus, P. zeae, Quinisulcius acutus, Rotylenchulus reniformis, Scutellonema cavenessi, S. clathricaudatum, Tylenchorhynchus acutus, and T. parvus.

References

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