Sorghum × drummondii (Sudangrass), is a hybrid-derived species of grass raised for forage and grain, native to tropical and subtropical regions of Eastern Africa. The plant is cultivated in Southern Europe, South America, Central America, North America and Southern Asia, for forage or as a cover crop.
It is distinguished from the grain sorghum (Sorghum bicolor) by the grain (caryopsis) not being exposed at maturity.
An important annual summer grass planted for pasture, silage, green chop and hay. Importance of sudangrass is expected to increase with sorghum-sudangrass hybrids yielding more forage than either parent. In the US Gulf States, the hybrids are among the most popular summer annual grazing crops.
Under certain conditions, this grass can develop lethal concentrations of HCN. High levels of available soil N and low levels of P seem to increase the poison (Watt and Breyer-Brandwijk, 1962). Dhurrin is also reported (List and Horhammer, 1969–1979). Nitrate poisonings and photosensitivities are also reported.
Tufted annual grass with heavy tillering but no rhizomes; culms slender, to 3 m tall, 3–9 mm in diameter; leaves numerous, up to 100 per clump, long, broad to narrow; panicles open, twice as long as broad, 15–75 cm long; spikelets not easily shed making seeds easily collected; glumes (hulls) around seed-buds with bristle-shaped tips, often purplish when in flower; bristles break off in threshing; seeds pale yellow when ripe. Seeds 121,275/kg. Sudangrass only develops fibrous roots and never becomes a noxious weed.
Originally from the Sudan where it is a weed of cultivated land, and only occasionally grown as fodder. Introduced from Africa to US in 1909, and from US introduced to South America, Australia, South Africa, Central and North Europe. In US grown mostly from southern Texas to Minnesota and North Dakota in the central grassland regions.
Ranging from Cool Temperate Steppe to Wet through Tropical Very Dry to Dry Forest Life Zones, sudangrass is reported to tolerate annual precipitation of 2.0 to 21.4 (mean of 37 cases = 9.8), annual temperature of 7.8 to 27.5°C (mean of 37 cases = 17.4), and pH of 4.9 to 8.2 (mean of 32 cases = 6.6). Sudangrass has a very wide range of adaptation, growing where summers are hot with a fair summer rainfall. Crop is very drought-resistant. Plants grow rapidly from late seeding. Not suited to cool humid temperate regions or to more humid regions in subtropics and tropics. Most favorable temperature for growth ranges from 25–30°C, with minimum ca 15°C. Sudangrass does not tolerate frost and is killed when the temperature drops to 3–5°C below the freezing point. Grows well under irrigation in hot dry regions. Rarely grown above 2700 m in southwest US, and less so farther north. Adapted to wide range of soils from heavy clays (not cold and wet) to sands, but requires fertile land to give heavy yields. Does not tolerate alkaline, saline, or solonetz soils.
Sudangrass is an excellent seed producer in all but humid areas. Seed broadcast or close-drilled. Low seed rates give as good yields as higher rates because of heavy tillering. Rates vary in different areas: in US, dryland planting, 20–25 kg/ha broadcast, humid 12–15 kg/ha broadcast or 3–8 kg/ha drilled; in India, 16–24 kg/ha broadcast or drilled; in Kenya, 20–30 kg/ha broadcast or drilled. When drilled in rows, spacing between rows may vary from 18 cm in Kenya to 90–105 cm elsewhere. A firm seedbed is desirable. Seed should be sown when soil is warm in late spring or early summer. Seeds may be drilled to a depth of 1–3 cm. Seedlings emerge in less than a week when conditions are warm and moist (Bogdan, 1977). Usually seeded alone in low-rainfall areas; often combined with soybeans in more humid areas. Also intercropped with cowpea and velvet beans. In India, often grown in rotation with tobacco, cotton, sugarcane, and groundnuts. In Africa, may follow groundnuts. In US, South Africa, and Australia, often precedes fallow or leguminous crop. Fertilizer requirements of sudangrass similar to those of annual grass crops or corn. Sudangrass grows rapidly; sufficient nitrogen at planting time helps insure establishment and hasten development. On any soil, some complete fertilizer is advisable for higher yields. Usual recommendation per ha in the Northeast is 165–275 kg of 10-10-10; in Midwest, 220–330 kg of 3-12-6 or similar ratio, and in irrigated lands of the West, 33–66 kg of nitrogen. Phosphorus and potassium should be applied if deficient. Barn-yard manure is useful also: In India ca 20 MT/ha is recommended. It also responds well to sewage irrigaton. Hybrid sorghum seed are produced from female plants that are male sterile, that is, the flowers of such plants do not produce viable pollen, and so are not self-pollinating. Male flowers of another cv are grown in rows alongside the female rows, thus providing the pollen for producing the hybrid seed (Reed, 1976).
Crop should be rotation grazed with other pastures or divided into subdivisions that are rotated. Sudangrass and sorghum-sudangrass hybrids are usually ready for grazing 5 or 6 weeks after planting. Plants are palatable and readily eaten at the early heading stage, but regrowth will be better when the crop is grazed before heading starts. To avoid HCN poisoning, sudangrass should not be pastured until it is 45–60 cm high. When grazing is begun, stock sudangrass heavily so it will be grazed down before heading starts. If fields reach 100 cm or more before livestock can graze them, crop should be harvested for silage. For green chop, cut plants down to a 15 cm stubble, making the first cut just before the heading stage to insure good regrowth. Highest hay yields are obtained when crop is harvested with seed in the soft-dough stage. Because curing is difficult at this stage, it is more practical to harvest at boot stage when plants are 75–100 cm tall. Use of a hay crusher will reduce drying time and give higher quality hay. Feed value of good sudangrass hay is about equal to that of millet, timothy, johnsongrass, and other non-legume roughages. From 2–4 cuttings can be made per season depending on region.