Sorghum (genus Sorghum) refers to various species of grasses (family Poaceae) that are cultivated as food crops. Because the relationships among the various species and their hybrids are highly complex and not well understood, the cultivated grain sorghums are usually named as Sorghum bicolor.
Sorghum is a tropical grass, well adapted to high productivity in a hot and dry climatic regime, and water efficient (water transpired per unit of atmospheric carbon dioxide fixed during photosynthesis). The wild progenitors of domesticated sorghum are thought to have inhabited the savannah of northern and central Africa, and perhaps India. Wild sorghum still occurs in these regions and their grains are gathered for food by local people. Sorghum was domesticated as a grain-crop approximately 5,000 years ago. Modern varieties grow 3-15 ft tall (1-5 m). The grains are born in a dense cluster (known as a panicle) at the top of the plant.
Sorghum is one of the world's major cultivated crops, ranking fourth among the cereals. In 1999, about 113 million acres (45.9 million ha) of sorghum were grown worldwide, and total production was 74.9 million tons of grain (68.1 million tonnes). Most of the world's sorghum crop is grown in Africa, where it is a leading cereal (although surpassed during the twentieth century by maize (Zea mays) in many countries).
There are four main cultivated groups of sorghum:
- The grain sorghums are ground into flour for baking bread and cakes, boiled as a gruel, fermented into beer, or fed to livestock. Sorghum grain is highly nutritious, containing about 12% protein. Grain sorghums are by far the most important sorghum crop.
- The sweet sorghum contains a high concentration of sucrose in its stems and is used to make table sugar in the same way as sugar cane (Saccharum officinarum). However, the sorghum sugar is not usually crystallized, but is boiled down into a dark-brown syrup similar to molasses.
- The forage sorghums are used directly as animal feed or they are chopped and fermented to manufacture silage.
- The broom-corn sorghums are cultivated for their thin, wiry, brushy stalks that are bound into "corn" brooms. This is no longer a common use, as natural-fiber brooms have been replaced by synthetic ones.