260 



COVER-CROPS 



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 

 10 the kind of crop to be grown 

 under the varying conditions of 

 climate, Iocati»n and cropping : 



Fig. 369. Root habit of (top) 

 crimson, (middle^mammoth 

 closer, (bottom) winter 

 vetcb. Ooiaell Exp. Sta. 



COWPEA 



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. 



COWPEA. Vigna unguiculata, Walp. 

 Leguminosce. Figs. 370, 371. 



By J. F. Duggar. 



A summer-growing annual more closely 

 related to the bean than to the pea, 

 grown for forage, for green-manuring 

 and cover-cropping, and sometimes for 

 human food. The habit of the plant 

 varies greatly, some varieties being 

 erect or bush-like and others distinctly 

 trailing. All intermediate forms occur, 

 and the habit is dependent not only on 

 variety, but on soil, time of planting 

 and climatic conditions. The cowpea is 

 never a true climber, being without 

 tendrils, but its slender runners twine 

 around adjacent objects. The leaves are 

 three-foliolate, and somewhat similar in 

 shape and appearance to those of the 

 common garden bean. The ilowers are 

 usually whitish or whitish purple, some- 

 times with a yellowish cast. The pods 

 are normally of straw color, but are 

 sometimes purplish or dark. They vary 

 in length from five to ten inches and 

 contain numerous edible seeds. The 

 seeds are usually kidney-shaped or 

 roundish, but in some varieties the 

 ends are slightly truncated. 



The cowpea, although belonging to 

 the genus Vigna, is closely related to 

 species of the section Strophostyles of 

 Phaseolus. It is a native of India and 

 the region northwestward to thesouthem 

 part of the Trans-Caspian District, but 

 has been a cultivated crop for two 

 thousand years or more. It was intro- 

 duced into the West Indies in the latter 

 half of the seventeenth century, and 

 began to be cultivated on the mainland 



