Plant vegetation contributes to soil organic matter, improves soil tilth and reduces the leaching of plant nutrients. Several forage legumes can be used to provide temporary soil cover. Properly inoculated forage legumes will furnish nitrogen to the crops which are subsequently grown. This nitrogen contribution by legumes should be an important consideration in the selection of crops for soil cover.
Legumes provide excellent soil cover and substantial nitrogen when used as green manure crops.
Table 1 shows the quantity of nitrogen contained in the plant parts of red clover, alfalfa and sweetclover during the fall following seeding and for a range of dates the following spring. The nitrogen and dry matter of the legume parts will vary with the stage of growth. During the fall of the seeding year, the total amount of nitrogen will be greatest in sweetclover with lesser amount in red clover and alfalfa. The following spring, sweetclover will still contain the greatest amount of nitrogen, followed by alfalfa and then red clover. A summation of 14 years of Ohio data indicates corn yields following alfalfa and sweetclover were equal when both crops were plowed down one year following seeding.