Pollination.—The cowpea is self-pollinated. Dodson made notes of the insect visitors, and concluded that insects were seldom concerned in bearing pollen from bloom to bloom. Artificial cross-pollination is exceedingly difficult in the field, but a larger percentage of hand-pollination is successful when the plants are grown in a greenhouse.
Companion-cropping.--Since the leaves of the cowpea easily fall off in curing, unless weather conditions are altogether favorable, it is some times advantageous to grow cowpeas in connec tion with some grass crop, the presence of which makes curing quicker and entangles the leaves, thus preventing their loss. For this purpose the latest varieties of millet, especially German millet, are satisfactory for mixing with the early varie ties of cowpeas, sowing one to one and one-half pecks of millet per acre with one bushel or more of cowpeas. Soybeans are sometimes grown in connection with cowpeas. Many southern farmers prefer a mixture of cowpeas and amber sorghum, about one bushel of each per acre. The admix ture of sorghum greatly increases the yield on fair or good land, but somewhat increases the difficulty of curing the forage. A volunteer growth of crab-grass is, perhaps, in the Gulf states, the most generally satisfactory addition to cow pea hay.
A satisfactory mixture for the silo consists of drilled corn and cowpeas, the latter sometimes being drilled in several weeks after the planting of the corn. Although the cowpeas usually con stitute the smaller part of this forage, their presence serves to increase the percentage of protein in the silage.
Manuring.—The cowpea is most useful on the poorest grades of land, but often needs the help of commercial fertilizers. In the South, the most general requirement is for phosphoric acid, although on some poor and very sandy soils the addition of potash as well as phosphate is profitable. Tests in Delaware and Connecticut indicated that pot ash, which was used at the rate of 160 pounds (muriate of potash) per acre, was the principal fertilizer needed. A common application is 200 to 400 pounds of acid phosphate per acre, to which, on soils needing potash, may be added fifty pounds of muriate of potash or an equivalent amount of kainit. The cowpea is a leguminous plant, and so, after reaching the stage at which its roots are abundantly supplied with tubercles, derives its nitrogen very largely from the air. Hence, the use of nitrogenous fertilizers is not generally very economical, though the cowpea, in common with nearly all other plants, thrives best in the pres ence of vegetable matter, and profits greatly by an application of stable manure, of which, how ever, more advantageous use can usually be made.
The yield is very slightly increased by applications of nitrate of soda, and nitrogenous fertilizers have little effect on the composition of the resulting forage. In one test at the Connecticut Storrs Experiment Station ( Report 1893 ), potash not only increased the yield but increased the per centage of protein, in the forage.
Harvesting.—In curing cowpea hay, the same rules obtain as in curing clover hay. Especial care must be taken to leave the cut forage exposed to the sun in the swath for as short a time as practi cable, the curing being completed in cocks, or in such other way as to protect the bulk of the hay from long exposure to the sun. No definite rule can be given, but it is usual to rake the hay twenty four to thirty-six hours after mowing and to pile it in cocks the afternoon of the second day after mowing. Here in fair weather it should remain for two or three days, at the end of which time the cocks may be opened for a few hours before being hauled to the barn.
One method of hay-curing is thus described in Bulletin No. 40, of the Mississippi Experiment Station : "The mower is started in the morning as soon as the dew is off and run until noon. . . . As soon as the top of the cut vine is well wilted the field is run over with a tedder. . . . When the crop is very heavy the tedder is used a second time. Vines that have been cut in the morning and teddered in the afternoon are usually dry enough to put in small cocks the next afternoon, and if the weather promises to be favorable they are allowed to remain in the cocks two or three days before they are hauled to the barn. If it should rain before the vines are put in cocks they are not touched until the surface is well dried, and are then tedded as though freshly cut. We find the only safe plan is to put the hay for a few w...ks in a stack covered with straw, or, still better, in a barn, where it should not be piled too deep. After a month it may be packed without danger of finding moldy or dusty hay in the cen ters of the bales." Some persons store cowpea hay in the barn when merely well wilted, and disavow any fear of spontaneous combustion or molding. When this is done it is necessary that the crop be nearly mature, about one-half of the pods having assumed a straw-color; that there be no external moisture on the plants when placed in the mow; and that the hay be not moved, no matter how hot it may become, since forking over the hay would admit additional oxygen that would facilitate fermenta tion or combustion. Until more is known of the conditions under which this procedure may be safe, it cannot be generally recommended.