The New International Encyclopædia/Rotation of Crops
ROTATION OF CROPS. The practice of growing various crops from one year to another upon a given field. This practice is followed for the sake of convenience in farm work, and for the purpose of maintaining and increasing the fertility of the soil. The theory of rotation is bused on such considerations as the following: Plants differ much in habit of growth and in the proportion of the different elements which they draw from the soil. Deep-rooted plants have a beneficial effect on the physical condition of the soil and are capable of obtaining food and moisture from the subsoil at comparatively great depths, while shallow rooted plants do not enter the subsoil to such an extent and are, therefore, more dependent upon the surface soil. The quantity and proportion of the crop remaining upon the soil ready to be turned under by the plow differs with the various crops. The cultivation of hoed crops, such as Indian corn, tends to free the land from weeds; leguminous plants enrich the soil in nitrogenous plant food by assimilating the free nitrogen of the air (see Clover); and fall-growing crops take up the available nitrogen from the soil and thus prevent its leaching away by the rains of winter and spring. Furthermore, plants having a long season of growth are better adapted to soils with a small supply of available plant food than rapidly growing plants, which need an abundance of available material during their short period of vegetation. The crops consumed upon the farm tend more to maintain fertility than those which are sold; and, finally, crops differing in season, cultivation, and growth allow a convenient arrangement of the farm work throughout the year.