Source: Magness et al. 1971
Grain sorghum was grown on 13,902,000 acres in the United States (average for 1966-67), mainly in the Central and Southern Plains States. Yields for the two years averaged 53.2 bushels per acre for a total average production of about 740 million bushels. World-wide, grain sorghum is grown on more than 100 million acres. China, India and Africa grow large quantities. In the United States most of the grain sorghum is used as livestock feed, but in the Orient and Africa most is used as food.
Sorghum culture goes back to antiquity with Egypt being an early area. Grain sorghums grown in this country mainly trace to African origins. Although they were brought here during early colonial days they did not become important crops until farming developed in drier sections of the United States. They generally outyielded other grains under conditions of limited moisture.
Grain sorghum plants are coarse annual grasses. Nearly all of the varieties grown in the United States are so-called dwarf types, with stems under 5 feet in height and suitable for harvesting with combines. In other countries many taller-stemmed kinds are grown. Leaves are relatively broad, bave numerous but small stomata, and are covered with a waxy bloom. They tend to roll along the midrib under moisture stress. Thus the plant is more drought resistant than most other grains and requires less water per pound of dry matter produced.
Flowers and seeds are borne in relatively dense panicles that vary from 3 to 20 inches in length and up to 3 inches in width. The panicle is enclosed in a rather strong sheath until just before the first flowers open. Branch stems in the panicle rise in whorls and inay be few or many. They are also variable in length, resulting in variable density of the panicle. Spikelets are partially enclosed in two rather short, thick glumes. Each spikelet contains two flowers, only one of which is usuallv fertile and sets a seed. The fertile flower consists of a thin lemma and thin palea, and inside these the stamens and pistil - the latter developing into the kernel. The lemma may be awned or awnless. When threshes the seed separates from the floral bracts as in wheat.
The kernels are small, averaging about 0.66 the weight of wheat grains. Weight of 1000 sorghum grains is mostly between 20 and 30 grams. Kernels are generally near round to broad-conic in shape. The grain consists of about 6 percent bran, the pericarp or surface layers; 10 percent germ; and 84 percent endosperm, which is largely starch. In protein content, sorghum is higher than corn and about equal to wheat. In fat content it is lower than com but higher than wheat.
Grain Sorghum Groups
Grain sorghum varieties are classed in seven agronomic groups, as follows:
Kafir sorghums, originally from South Africa, have thick, juicy stems, large leaves, and awnless cylindrical-shaped panicles. Seeds may be white, pink or red and are medium in size.
Milo sorghums, originally from East Africa, have stems that are less juicy than in Kafir. Leaf blades are wavy with a yellow midrib. Heads are bearded or awned, compact, oval in shape. Seeds are large, pale pink to cream in color. Plants tend to be more tolerant to heat and drought than the Kafirs.
Feterita sorghums came from Sudan. Leaves are sparse in number.
Stems are slender and dry. Panicles are compact and oval in shape. Seeds are very large for sorghum, chalky white in color.
Durra sorghums are from the Mediterranean Area, the Near East, and Middle East. Stems are dry. Panicles are bearded and hairy and may be compact or open. Seeds are large and flattened.
Sballu sorghums from India have tall, slender, dry stems. Heads are loose. Seeds are pearly white in color and late maturing, thus requiring a relatively long growing season.
Koaliang sorghums, typical of those mainly grown in China, Manchuria and Japan, have slender, dry, woody stems with sparse leaves. Panicles are wiry and semicompact. Seeds are brown and bitter in taste.
Hegari sorghums from Sudan are somewhat similar to Kafirs but have more nearly oval panicles, and plants that tiller profusely. Seeds are chalky white.
In the United States most varieties have been derived from crosses involving Kafir and Milo. Other groups have also entered into some varieties, so the varieties now grown are generally not typical of any specific group. Most sorghums now being grown in this country are from hybrid seeds, made possible by the finding and isolation of male sterile strains. When the male-sterile line is planted alongside suitable lines with fertile pollen all the seed produced on the male-sterile line is hybrid. Use of such seed, coupled with improved agronomic practices, have resulted in recent average yields which are more than double those being obtained even as late as from 1952 to 1956.
Nearly all the sorghum grain consumed in the United States is used for livestock feed. Of the approximately 740 million bushels produced annually in 1966 and 1967 about one-third was exported--mainly to Japan, India and Europe. Most of that exported was probably used as food. For food use, the grain may be roughly ground and made into breadlike preparations, used after grinding and stewing as a mush or porridge, or made into flour for mixing with wheat flour for breads. Varieties with waxy endosperms are a source of starch having properties similar to tapioca. The grain is also a source of native beers, particularly in Africa. For feed use, sorghum grain should be ground for most classes of livestock, since the grains are small and relatively hard. In feeding value it is almost equal to kernel corn.
Some quantities of grain sorghums go into industrial uses in this country. Starch is manufactured by a wet-milling process similar to that used for corn starch. (See under corn.) The starch is then made into dextrose for use in foods. Starch from waxy sorghums is used in adhesives and for sizing paper and fabrics, also in the "mud" used in drilling for oil. The grain is also a source of grain and butyl alcohol.
Like the forage sorghums, the green grain sorghum plants contain the glucoside dhurrin, which converts to prussic acid (HCN) and is poisonous to livestock. For this reason grain sorghums are not suitable for pasturage.