This is not total nitrogen in the plant, which includes nitrogen taken up from the soil. Some yearly variations in nitrogen fixations are evident. For example, winter wheat yield after peas with no nitrogen fertilizer was 93 percent of the yield after spring barley with nitrogen fertilizer. This illustrates some of the yield benefit that can be obtained from legumes in the crop rotation. Differences will be evaluated in 1985 in terms of the amount of residue nitrogen that is available to the cereal crop the following season.
Legumes being studied include peas, chickpeas and fababeans.
Yield of winter wheat planted in the fall of 1983 will be evaluated in relation to moisture depletion by the legume and nitrogen contribution from the legume. Three tillage treatments consisting of shallow tillage, chemical kill and moldboard plow will be tested for each rotation. Winter wheat will be planted in fall of 1985 under three nitrogen fertilizer rates to evaluate winter wheat production in terms of type of legumes, tillage and nitrogen rate. A no-till drill will be used that places the bulk of fertilizer below the seed in the chemical kill treatment.