The knowledge gained through experiment sta tion work as to the usefulness of cover-crops, is constantly increasing, and they are now considered an important part of rational agricultural prac tice.
Kind of crops to use.
The principle that should govern in the use of cover-crops is to employ such crops as may accom plish the special purposes desired. To get the best results, a cover-crop should be used when there is a period in a succession of crops in a rotation when the land would be likely to lie bare for any consider able period, or, as in the case of orch ards, when it is desirable to increase the vegetable matter in the soil and to retard the vegetative growth of the trees and bushes, and thus to encourage a more complete maturity of the plant.
The kind of crop to plant must be determined by the local conditions and the local needs ; that is, whether a grass, cereal, legume, or cruciferous plant shall be used, will depend on whether the habits of growth and char acteristics of the plant will accomplish the purpose desired. For example, in the southern states, Bermuda-grass is admirably adapted to prevent erosion of land, yet this crop would not be recom mended for northern conditions. In Delaware, and in certain other of the middle states, crimson clover is gener ally seeded in corn as a cover-crop. It is hardy, grows well in the fall, and protects the soil during the winter ; in addition, it starts early and grows rap idly in the spring, accumulating a large mass of vegetable matter containing nitrogen, in time to plow down for a spring crop. The conditions in these states are favorable for the use of crim son clover as a cover-crop, whereas farther north the plant is not hardy and may serve as a cover-crop only in the fall. In the more northern sections, therefore, wheat or rye would be more desirable, as it will serve as a cover during the fall and continue to grow through the winter and early spring, absorbing and retaining soluble plant food and gathering useful vegetable matter.
In market-gardening, when it is necessary to plant early in spring, such crops as turnips, rape, oats, Canada peas, cowpeas, or soybeans, which die after freezing weather, are serviceable as fall cover-crops, because they accu mulate large quantities of vegetable matter, cover the land with a mulch during the late fall and early win ter, and are in condition to decay rapidly when the ground is plowed, which frequently may be done in early March.
Literature.
The following bibliography of some of the experiments conducted in this country will serve as a guide so the kind of crop to be grown under the varying conditions of climate, location and cropping; Tennessee Experiment Station, Bulle tin No. 4 ; Nebraska Experiment Sta tion, Report 1899, pp. 50-61 Canada Experimental Farms, Ottawa, Canada, Report 1901, pp. 140-152 ; Ontario Agri cultural College and Experiment Station, Report 1904 ; Cornell Experiment Sta tion, Bulletin No. 198 ; Report of the Secretary of Agriculture, Nova Scotia, 1902, Part I, pp. 70-90 ; Massachusetts Experiment Station, Bulletin No. 82 ; Missouri Fruit Experiment Station, Bul letin No. 4; Delaware Experiment Sta tion, Bulletins Nos. 60 and 61 ; Michigan Experiment Station, Special Bulletins Nos. 27 and 30; Connecticut Experiment Station, Bulletin No. 149 ; Proceedings of Western New York Horticultural Society, 1901, pp. 12-17 ; American Agriculturist, 1902, pp. 79 and 100. The term cover-crop was first used in this signification by Bailey in 1893, Cornell Bulletin No. 61.