ALL CROPS DEMAND CONDITIONS
Alfalfa, like corn and cotton, demands certain conditions of the soil and certain constituents in that soil. Every crop demands its certain foods. All crops except alfalfa and the other legumes obtain practically all their food, including nitrogen, from the soil. The latter crops use nitrogen but get it from the air. Alfalfa takes nitrogen from the soil only during the first few months of its growth, and thereafter not only takes its own necessary supply from the air, but a large surplus which it stores in the soil, available for whatever crop may follow. Other crops take much nitrogen from the soil, but contribute nothing to its enrichment.