Rotation of crops.
In order to maintain soil fertility, and at the same time to make the greatest profit in farming, a practicable and scientific rotation of crops should include the following : (1) Grasses and perennial legumes.
(2) Pasture, with an addition of manure one or two years previous to breaking the sod.
(3) Intertilled crops.
(4) Small grain crops, with green-manuring crops planted in the stubble after harvest.
For a self-sustaining farm, small grain crops must be grown. Often they are the greatest money-making crops ; hence they most be given a prominent place in the general crop rotation system. Intertilled crops are often the money-making items of the farm, also, and they are useful in a rotation plan in order that the land may be cleared of weeds. Especially is this true in a locality where small grain is the main crop. Cultivation also con serves the soil moisture and develops the fertility of the soil.
Pasture must be had on every farm carrying live-stock, and it is essential that it be made part of the regular crop rotation. Many soils become too light and mellow by continuous cropping and need the trampling of stock to firm them. Much more grass can be produced on tillable lands when the pastures are kept fresh and new, and the increase of fertility and improvement of soil texture result in larger crops of corn and grain when the meadow or pasture is broken and planted again to these crops. In some sections of the United States permanent pastures develop the best sod, and on many farms certain fields may be kept more profitably in grass than in any other crop ; but such fields will not enter into the regular crop rotation system.
A convenient and desirable time to manure land is while it is being used as meadow or pasture. If the manure is applied a year or so before breaking, it will stimulate the growth of grass and cause a greater production of hay or pasture. Meanwhile, the soil is enriched by an increased root-growth and the formation of more humus. Besides these beneficial results, some plant-food will be supplied by the manuring for the use of the first crop that is grown on the breaking, at a time when available plant-food is much needed, because the larger part of the fertility in new breaking is in an unavailable condition and cannot be used readily by the new crop.
Soils in which the organic matter and humus are deficient may be improved in fertility and texture by green-manuring. A cheap and practical method of green-manuring is to plant a crop adapted to this purpose (the annual legume crops, such as cowpeas, soybeans, field-peas and vetches being preferred) in the grain stubble immediately after harvest. The method at the Kansas Experiment Station is to follow the binder directly with the drill ; thus, when the harvest is finished the field has been replanted. Cowpeas, rape or sorghum seeded in this way usually make a good stand and an excellent growth, and furnish forage or pasture, or the crop may be plowed down for green-manure or left as a winter cover.
It is necessary, in carrying out permanent plans for crop rotation, to have fields of nearly equal area, in order to grow about the same acreage of the several crops each year, thus making it possible to keep a certain number of live-stock, and from year to year to have regularity and uniformity in the farming business.
In order to demonstrate the working of practical systems of crop rotation, as outlined, assume for illustration a farm of 160 acres, divided into eight equal fields, as shown in the diagrams : four years at a time requires that one field be seeded to grass every two years and that one grass field be plowed every two years and planted again to wheat, requiring sixteen years before the whole farm shall have received a rotation with grass.
It will be observed that the crops growing on the eight fields each year are the same as the "order of crops on each field" in eight years. By carrying out successfully the above plan of rotation on a 160-acre farm, the farmer will raise each year SO acres of wheat, 40 acres of grass and clover (20 of which may be used for pasture), 20 acres of small grains other than wheat, and 20 acres of forage crops, part at least consisting of annual legume crops. Each year 20 acres of grass land is given a dressing of manure, and a 20-acre field in wheat is renewed in fertility by a crop of cowpeas or other green-manuring crop planted after the wheat is harvested. Meanwhile, once in eight years the whole farm will have been seeded to grass and clover, each field remaining in grass two years.