Yield and Nitrogen Use Efficiency of Cereal and Pulse Crop Rotation Systems in Central Montana.

Nitrogen (N) fertilizer expenditures represent one of the major production costs for winter wheat production in the northern Great Plains, and rotating winter wheat with field pea may reduce nitrogen input and the cost of the production system. However, tillage method may affect nitrogen use efficiency. This study investigated the effects of tillage and previous rotation crop on subsequent winter wheat yield and N use efficiency. Winter wheat was seeded following 1) summer fallow, 2) spring wheat, 3) spring pea harvested for seed, and 4) winter pea harvested for hay. Each field was split into no-till and conventional sweep tillage treatments. Four levels of N fertilizer (0, 45, 90, and 134 kg N ha^-1) were applied to spring and winter wheat, and no N was applied to peas. Tillage greatly influenced winter wheat yield. The sweep tillage treatment had a greater yield than the no-till treatment. Yield response to N application differed among the four crop rotations. Winter wheat planted after spring wheat produced the least yield at all N levels, while winter wheat planted after winter pea had the greatest yield at 0 and 45 kg N ha^-1, indicating that N was released from winter pea residues. Winter wheat yields following fallow, spring pea, and winter pea were similar at 90 and 134 kg N ha^-1, but the yields were significantly greater than that following spring wheat. Nitrogen uptake and N budgets were also analyzed and will be discussed.