Biological Nitrogen Fixation, 1924-1974

Crop rotation was practiced in ancient times by alternating the use of leguminous and nonleguminous plants. The basis for the benefit derived from this practice was not understood, but it was observed empirically that crops were improved and the condition of the soil was maintained better with rotation than by continual cropping with nonleguminous plants. Rotation was recognized as good husbandry, but it remained for Boussingault to offer an explanation of the benefit in the 1830's. He estab- lished one of the earliest agricultural experiment stations and demonstrated in the greenhouse that clover and peas increased their nitrogen content when grown on sand that was virtually free of fixed nitrogen. His field experiments likewise supported the view that leguminous plants could use N. from the at- mosphere.