Source of Digital Item
Before we can appreciate the cowpea, or any of the legumes (pod-bearing plants), it is quite necessary that we fix clearly in our minds the following four laws of the great German chemist, Justus Von Liebig, with reference to soil fertility:
First. A soil can be termed fertile only when it contains all of the materials requisite, or necessary for the nutrition of plants in the required quantity and in the proper form.
Second. With every crop a portion of these ingredients is removed. A part of this portion is again added from the inexhaustible store of the atmosphere; another part is lost forever if not restored by man.
Third. The fertility of the soil remains unchanged if all the ingredients of a crop are given back to the land. Such a restitution is effected by fertilizers.
Fourth. The fertilizers produced in the course of animal husbandry are not sufficient to maintain permanently the fertility of a farm; it lacks the constituents which are annually exported in the shape of grain, hay, milk, and livestock.
In connection with the above facts, every progressive farmer recognizes that certain crops exhaust or make his soil poorer, and certain others build it up or make it richer. He is also aware that a better crop follows a pod-bearing one, such as peas, beans, clovers, vetches, peanuts, etc.; therefore, they are absolutely indispensable in a wise crop rotation, and in the rational feeding of both man and beast.