INOCULATING THE SOIL
It has been found where alfalfa shows thrifty vigor, is making a good stand, and is at least two years old, that on the roots are little nodules or wart-like protuberances. On fields where the alfalfa is unthrifty or failing to make a good stand, examination will probably fail to discover any of these nodules. Scientists tell us that these nodules are the homes of bacteria, microscopic vegetable organisms obtaining their sustenance from the nitrogen of the air and the starch of the plant; that they collect much more nitrogen than they need, the over-supply being taken up by the alfalfa, which, after these nodules are formed and occupied, takes no more nitrogen from the soil, but annually stores about its roots more from the air, thus adding to the nitrogen supply in the soil instead of taking from it as do all other farm crops except the legumes. Each legume—clover, alfalfa, cowpeas, etc.—has a distinct species of bacteria, or at least bacteria with a distinct development, excepting, as has been found, that Sweet clover (Melilotus alba) and Bur clover (Medicago denticulata) develop the same species as does alfalfa.