If you sow wheat in the autumn it is ready to be harvested in time for planting cowpeas. Plow or disk the wheat stubble, and sow the same field to cowpeas. If the wheat crop has exhausted the greater part of the nitrogen of the soil, it makes no difference to the cowpea; for the cowpea will get its nitrogen from the air and not only provide for its own growth but will leave quantities of nitrogen in the queer nodules of its roots for the crops coming after it in the rotation.
Fig. 27. Cowpeas and Corn—October
If corn be planted, there should be a rotation in just the same way. The corn plant, a summer grower, of course uses a certain portion of the plant food stored in the soil. In order that the crop following the corn may feed on what the corn did not use, this crop should be one that requires a somewhat different food. Moreover, it should be one that fits in well with corn so as to make a winter crop. We find just such a plant in clover or wheat. Like the cowpea, all the varieties of clover have on their roots tubercles that add the important element, nitrogen, to the soil.
From these facts is it not clear that if you wish to improve your land quickly and keep it always fruitful you must practice crop-rotation?
An Illustration of Crop-Rotation
Here are two systems of crop-rotation as practiced at one or more agricultural experiment stations. Each furnishes an ideal plan for keeping up land.
| First Year | Second Year | Third Year | |||
|---|---|---|---|---|---|
| Summer | Winter | Summer | Winter | Summer | Winter |
| Corn | Crimson Clover | Cotton | Wheat | Cowpeas | Rye for pasture |
| or | |||||
| Summer | Winter | Summer | Winter | Summer | Winter |
| Corn | Wheat | Clover and grass | Clover and grass | Grass | Grass for pasture or meadow |
In these rotations the cowpeas and clovers are nitrogen-gathering crops. They not only furnish hay but they enrich the soil. The wheat, corn, and cotton are money crops, but in addition they are cultivated crops; hence they improve the physical condition of the soil and give opportunity to kill weeds. The grasses and clovers are of course used for pasturage and hay. This is only a suggested rotation. Work out one that will meet your home need.
EXERCISE