Grass crops

(agriculture) Plants cultivated as forage and grain to be consumed by domestic livestock.

Members of the family Gramineae cultivated as forage and grain for consumption. The grasses are the most useful of all the plants that cover the Earth. The cereal grasses supply directly three-fourths of the energy and over half of the protein in food consumed by humans. Indirectly, these cereals together with the forage grasses supply most of the food for the domestic animals that provide milk, meat, eggs, and much of the draft power required to grow crops. See also Barley; Cereal; Corn; Millet; Oats; Rice; Rye; Sorghum; Wheat.

The bamboos are of vast importance in the Indo-Malay region, where they are used in building houses, bridges, furniture, rafts, water pipes, vessels for holding water, and so forth. See also Bamboo.

The grasses protect soil from erosion and help conserve water resources. More than any other family of plants, the sod-forming grasses blanket golf courses, athletic fields, lawns, parks, and cemeteries with a protective covering that beautifies and enhances the environment. No other family of plants in the vast plant kingdom is so useful to humans. See also Erosion; Soil conservation.

Grass stems have solid joints (nodes) and leaves arranged in two rows, with one leaf at each joint (see illustration). The leaves consist of the sheath, which fits around the stem like a split tube, and the blade, which is commonly long and narrow. Seed heads are made up of minute flowers on tiny branchlets, often several crowded together, but always two-ranked like the leaves. The flowers are generally wind-pollinated. The seeds are enclosed between two bracts, or glumes, which remain on the seed when ripe.

A typical grass plant. (After P. D. Strausbaugh and E. L. Core, Flora of West Virginia, West Va. Univ. Bull., ser. 52, no. 12–2, pt. 1, p. 67, 1952)

The 600 genera grouped into 14 tribes that make up the grass family may be annual or perennial. Annuals and some perennial grasses are bunch grasses which spread only by seeding. Others, mostly perennials, also spread by creeping stems called stolons when above ground and rhizomes when below the soil surface. The creeping grasses form the best sods and surpass others for soil conservation; they are also the best turf grasses. All grasses have fine fibrous root systems that permeate the soil extensively to depths ranging from much less than 3 ft to more than 10 ft (1 to 3 m). The roots are short-lived, are continually being replaced, and in the process increase the organic matter content of the soil.

Grasses are distributed throughout the world. Annual species predominate in the adverse environments found in the deserts and the arctic areas. Temperature is the principal factor determining the distribution of perennial grasses. Perennial grasses are frequently classed as cool- or warm-season grasses depending upon the season in which they make their best growth.

Annuals and most perennial grasses reproduce sexually and are propagated by seed. Many of the grasses are cross-pollinated largely by the wind. In some species, cross-pollination is facilitated by self-incompatibility that occurs at variable frequencies. Most grasses produce perfect flowers containing both male and female organs. The male organs (anthers) must be carefully removed before they shed pollen to make controlled hybrids. A few species, largely tropical perennials, reproduce by apomixis, simply defined as vegetative reproduction through the seed. Apomictic seeds produce the same genotype as the plant that produced them. See also Flower; Pollination; Reproduction (plant).