Chapter 34

THE COWPEA

A Southern Legume.--The soils of the cold north are protected from leaching during the winter by the action of frost. The plant-food is locked up safely for another year when nature ceases her work of production for the year. Farther south, in the center of the corn belt, there are leaching periods in fall and spring and oftentimes during the winter, but winter wheat thrives and, in ordinary crop-rotations, covers much of the land that might otherwise lose plant-food. As we pass from the northern to the southern states, the preservation of soil fertility grows more difficult and at the same time the restoration of humus becomes easier. The heat makes easy the change of organic matter to soluble forms, and the rains cause waste, but the climate favors plants that replace rapidly what is lost. In the work of supplying land with fertility, directly and indirectly, the southern cowpea has an important place. It is to the south what red clover is to the north, and it overlaps part of the red-clover belt, having a rightful place as far north as the Ohio Valley, and portions of Pennsylvania.

Characteristics.--The cowpea is closely related to the bean, and is very unlike the Canada pea, which is a true pea, thriving only in a cool climate. The cowpea has been grown in the southern states over one hundred years, and the acreage is large, but it never has come into the full use it deserves. Being a legume, it stores up nitrogen taken from the air, and unlike red clover it makes its full growth within a short period of time. It can grow on land too infertile for most kinds of valuable plants, and on better land. The vines can crowd out nearly all varieties of weeds. The roots go to a good depth and are thickly covered with the nodules of nitrogen-gathering bacteria.

Varieties.--There are many varieties of the cowpea, and confusion of names prevails, although some stations have done good service in identification of individuals carrying a number of names. The very quick-maturing varieties adapted to northern conditions do not make as much foliage as the rank-growing ones that require a relatively long season, but some of them are heavy producers of seed.

There are varieties requiring six months of southern heat to bring them to maturity, and some failures attending the introduction of the cowpea into more northern latitudes have been due to bad selection. A few varieties reach maturity within two months of hot weather.

The trailing habit is affected by the soil, the bunch varieties tending to trail when grown on fertile land. When the crop is wanted for seed, the peas that do not trail heavily will prove more satisfactory. The selection of variety is a matter of latitude and purpose, exactly as it is with corn.

Fertilizing Value.--A heavy growth of the cowpea is worth as much to the soil as a good crop of red clover. When the equivalent of two tons of hay is produced, the roots and vines contain nearly as much plant-food as the roots and first crop of medium red clover that makes two tons of hay. Some analyses show a higher percentage of protein in cowpea hay than in clover hay, and the experience of many stockmen indicates that such is the case. The roots and stubble have somewhat less fertilizing power than in the case of the clover, and all thin soils should have the entire plant, or the manure from the hay, saved without loss.

Comparison is made on the basis of equal adaptability of soil and climate to clover and the cowpea. Going southward, the cowpea has the advantage, and northward the clover gains. It is in the overlapping belt that both should be freely used. The cowpea has distinct advantage over the clover in its ability to supply nitrogen and organic matter within a few months, and in its adaptation to very poor soils where clover would not make much growth. As a catch crop it has great value.

Affecting Physical Condition.--The cowpea has marked influence upon the physical condition of heavy soils, even when the vines are not plowed down. This is due in some degree to the roots, and probably more to the mulching effect of the vines during their growth. Heavy soils are made much more mellow by the cowpea, and when the crop is removed for hay, the stubble-land is easily prepared for a seeding to grass or small grain. When the growth is plowed down, the soil may be made too loose for seeding to small grain, but is put into prime condition for a tilled crop.

Planting.--The land should be fitted as it is for corn. Light, sandy soils require little preparation, and too often the seeding is made in a woefully careless manner, the chief dependence being placed upon sufficiently deep covering to insure germination. The ground should be fitted as well as it is for a cash crop, being made fine and smooth. A grain drill makes the seeding in a satisfactory manner, and the seed may be drilled solid or in rows for cultivation. When the crop is grown as a fertilizer or for hay, solid drilling is good, and about five pecks of seed gives a good stand of plants if peas are sound. Much cowpea seed is low in germination power, and the buyer should exercise caution. When a seed crop is wanted, two to three pecks of seed per acre, placed in drills 28 to 32 inches apart, make an excellent seeding, as cultivation can be given. The amount of seed varies with the variety. In northern latitudes a warm soil is to be desired, and cultivation gives better results when a seeding to wheat will be made on the pea-stubble.

There is evidence that the cowpea can make a heavy growth in soils too deficient in lime for red clover, and it gained its first prominence in southern Ohio on land that was failing to grow clover. It is the plant of adversity as well as prosperity, adding rich organic matter to thin soils, but making its full returns under better conditions. Lime applications on acid soils give increase in yields. Its one absolute requirement is heat, and in a cold summer its northern limit is markedly depressed.

Inoculation.--The inoculation of the soil with cowpea bacteria is necessary to best results in most regions new to the plant. Self-inoculation is quicker in the cowpea than in alfalfa because the vines carry some soil on them, and thus the dust in the seed crop may be rich in bacteria. However, most new seedings of the cowpea do not show a large number of nodules on the plant roots, and inoculation pays. In some cases it makes the difference between failure and success. Two hundred pounds of soil from an old field should be well harrowed into each acre of land when preparing for a cowpea seeding in a new region. The soils of the southern states contain the bacteria just as the states in the clover belt are supplied with clover bacteria.

Fertilizers.--The light soils of Maryland, New Jersey, and the southern states are not naturally rich in phosphoric acid or potash. The cowpea can draw its nitrogen from the air, but on all thin land it pays to use 200 to 300 pounds of acid phosphate and 50 pounds of muriate of potash per acre for this crop which should have a luxuriant growth for the soil's benefit. Such use of fertilizers is more profitable than their use on the crop which follows.

Harvesting with Livestock.--When the cowpea is made into hay, there is always danger that the most of the plant-food contained in it never will get back to the soil on account of a careless handling of the manure. The practice of pasturing with cows and hogs is excellent. The feed is rich, and the manure is left on the ground. There is a saving of labor.

If the full fertilizing value is wanted for the soil, the crop should be plowed down. The trailing varieties form a tangled mass that cannot be handled by an ordinary breaking-plow, but a stalk-cutter, run in the direction the plow will follow, makes plowing possible. Pasturing with cattle and hogs sufficiently to reduce the growth so that a plow can be used is good practice.

The Cowpea for Hay.--The hay is one of our most palatable feeding-stuffs. Livestock may reject it the first time it is put into the manger, but a taste for it is quickly acquired, and soon it is eaten greedily. The high content of protein makes it exceptionally valuable for young animals and milk cows, and the manure contains a high percentage of nitrogen. The difficulty in making the hay is a drawback, but this is over-rated. While rain discolors the vines and makes them unattractive in appearance, the hay remains more palatable and nutritious than good timothy, if the leaves are not lost in curing. When the first pods turn yellow, the crop should be harvested. The vines can be left in the swath until the top leaves begin to burn and then be put into windrows with a sulky hay-rake. The windrows should be small, the rake merely serving to invert half the vines upon the other half, bringing new surface to the sun. After another day of curing, the windrows should be broken up into bunches no larger than can be pitched upon the wagon by a workman, thus saving the trouble of disentangling the vines. If rain comes, the bunches should be inverted the following day. In dry, hot weather the curing proceeds rapidly, while in cooler latitudes or cloudy weather the curing may require a week. The chief point is to prevent undue exposure of the leaves to the sun, and this is accomplished by the turning. The hay will mold in the mow if not thoroughly well cured, unless placed in a large body in a deep, close mow that excludes the air. Some farmers use the latter method successfully, but the experimenter with the cowpea usually will fail, and should prefer thorough field curing, at the risk of some damage from rain and sun. The leaves are the most nutritious part of the plant, excepting the seed.

As a Catch Crop.--A leading use of the cowpea is that of a catch crop, either between other crops or in a growing crop, such as corn. Early maturing varieties can be brought in between main crops of the rotation in warm latitudes. The growth prevents the leaching of plant-food, shades the ground, adds nitrogen to the soil, smothers weeds, and produces material that is valuable as feed for livestock or an addition of organic matter to the soil. When the time that can be devoted to the crop is short, an early variety should be selected because its vines are far more valuable to the soil than an equal volume of a rank-growing variety that is not near maturity.

If this legume were used whenever opportunity afforded along the southern border of our northern states, and throughout the south, the faded color of soils, resulting from leaching rains, would be replaced by the darker colors that mark the presence of rich organic matter. It is one of nature's best allies in the maintenance of soil fertility.