Winter Wheat Response to Tillage and Crop Rotations in Central Montana.
Chengci Chen, Clain Jones, and Karnes Neill. Montana State Univ, Central Ag Research Ctr, HC 90 Box 20, Moccasin, MT 59462
For optimal yield, economic return and environmental protection, nitrogen (N) recommendations on winter wheat must be adjusted according to tillage practice, crop rotation, and projected yield. In this study, we investigate the effects of tillage, number of years of tillage, previous crop, and N input on winter wheat yield. Winter wheat was planted in the fields that had been in 1) long-term no-till, 2) first year transition to no-till, 3) long-term sweep tillage, and 4) first year transition to sweep tillage, following 1) summer fallow, 2) spring wheat, 3) spring pea, and 4) winter pea. Four levels of N fertilizer (0, 45, 90, and 134 kg N ha-1) were applied. Tillage greatly influenced winter wheat yield. Continuous tillage (sweep) had the greatest winter wheat yield, and the continuous no-till had the least yield. Winter wheat yield in the first year transition from sweep tillage to no-till was greater than the first year transition from no-till to sweep tillage in the spring wheat – winter wheat rotation, while no difference was observed in other crop rotations. Yield response to N application differed among the four crop rotations. Winter wheat planted after spring wheat received the least grain 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 grain yields obtained following fallow, spring pea, and winter pea were similar at 90 and 134 kg N ha-1, but were significantly greater than the grain yield following spring wheat.