3. Greater feeding value of the seed.
On the other hand, a stand of cowpea plants is surer in the case of soils that crust, and germination runs higher. Its climbing habit makes it better suited for growing with corn for forage. A less amount of leaves is lost in curing.
Fertility Value.—There are so many varieties of the soybean and the cowpea, and adaptation to soil and climate varies so widely, that a fair comparison is difficult to make. In cool latitudes the soybean is recognized as distinctly more profitable, making larger yields of vines and of seed. Where adaptation is equal, the cowpea makes a slightly larger growth of vines for hay, but the soybean gives a much richer lot of seed for use as grain.
When soil fertility is the chief consideration, the adaptation of climate and soil should decide our choice between these two legumes. There is no serious difference where conditions for each are equally good. In cool latitudes the soybean should be chosen. In the Ohio Valley it is usually to be preferred. The greater part of the organic matter and the plant-food is stored in the vines and seed.
Feeding Value.—The soybean makes a rich hay, surpassing clover, but it is coarse, and its unattractive appearance has caused many farmers to condemn it without trial. Livestock eat it greedily, and it is one of our richest coarse feeds. The curing is more difficult than in the case of the cowpea because the leaves drop early, and the plants must be harvested before they approach maturity.
Probably the large yield of rich seed is the most important feature of the soybean crop. A ton of the seed contains as much protein as a ton of old-process oil meal, and three fourths as much as a ton of cottonseed meal. A good crop of the soybean will yield 18 to 20 bushels of seed, and as the nitrogen may be obtained chiefly from the air, the protein from this crop will come to be a leading substitute for purchased protein feeds.
Varieties.—There are many varieties of the soybean, and their characteristics are modified by climatic conditions. Each region will find the varieties best suited to its purposes by tests. When hay is wanted, the variety should have fine stems and a leafy habit of growth. It may not be a good producer of seed, or able to hold the seed unshattered. The harvesting should be done when some lower leaves turn brown and before the pods are half filled. This stage of maturity should be reached early enough in the fall to insure some hot days for making the hay, and to permit harvesting in time for seeding to wheat. The preparation for wheat is made with the harrow and roller or plank drag.
When the soybean is grown for seed, the variety should hold the peas without undue shattering, and an erect grower is more easily handled without loss of the crop. Varieties for regions will vary, as do varieties of corn, according to climate.
The Planting.—Early varieties of the soybean in the south can be planted as late as mid-summer, but farther north a profitable crop requires nearly all of the summer heat. The planting may be made soon after the usual time of planting corn, or whenever the ground has become warm. The preparation of the soil should be more thorough than that often given the cowpea. Solid drilling of five pecks of seed per acre is satisfactory when the crop is for fertilizing purposes only, and gives an excellent hay on land free of weeds. When the crop is wanted for hay, however, wheat usually will follow, and it is much better to plant in rows and to give two or three cultivations so that the ground may be easily prepared for the wheat.
A seed crop should be grown in rows. Three pecks of seed in rows 28 inches apart is the usual amount.