This crop ranks third in value in the United States. It grows in cool, in temperate, and in warm climates, and in many kinds of soil. It does best in clay loam, and worst in sandy soils. Clogged and water-soaked land will not grow wheat with profit to the farmer; for this reason, where good wheat-production is desired the soil must be well drained and in good physical condition--that is, the soil must be open, crumbly, and mellow. Clay soils that are hard and lifeless can be made valuable for wheat-production by covering the surface with manure, by good tillage, and by a thorough system of crop-rotation. Cowpeas and other legumes make a most valuable crop to precede wheat, for in growing they add atmospheric nitrogen to the soil, and their roots loosen the root-bed, thereby admitting a free circulation of air and adding humus to the soil. Moreover, the legumes leave the soil with its grains fairly close packed, and this is a help in wheat growing. One may secure a good seed-bed after cotton and corn as well as after cowpeas and other legumes. They are summer-cultivated crops, and the clean culture that has been given them renders the surface soil mellow and the undersoil firm and compact. They are not so good, however, as cowpeas, since they add no atmospheric nitrogen to the soil, as all leguminous crops do. [Illustration: FIG. 194. ROOTS OF A SINGLE WHEAT PLANT] From one to two inches is the most satisfactory depth for planting wheat. The largest number of seeds comes up when planted at this depth. A mellow soil is very helpful to good coming up and provides a most comfortable home for the roots of the plant. A compact soil below makes a moist undersoil; and this is desirable, for the soil water is needed to dissolve plant food and to carry it up through the plant, where it is used in building tissue. There are a great many varieties of wheat: some are bearded, others are smooth; some are winter and others are spring varieties. The smooth-headed varieties are most agreeable to handle during harvest and at threshing-time. Some of the bearded varieties, however, do so well in some soils and climates that it is desirable to continue growing them, though they are less agreeable to handle. No matter what variety you are accustomed to raise, it may be improved by careful seed-selection. [Illustration: FIG. 195. SELECTING WHEAT SEED] The seed-drill is the best implement for planting wheat. It distributes the grains evenly over the whole field and leaves the mellow soil in a condition to catch what snow may fall and secure what protection it affords. [Illustration: FIG. 196. ADJOINING WHEAT FIELDS The yield of the lower field, forty-five bushels per acre, is due to intelligent farming]