Yield and Yield Components of Spring Wheat and Field Pea in Diversified Dryland Cropping Systems.

Available water, decreased soil quality, weed competition and plant diseases constrain dryland crop production in the northern Great Plains.  We initiated a field trial in 2004 comparing four crop rotations, with each component in a two-by-two matrix of tillage (conventional vs. zero tillage) and management (conventional vs. ecological) systems.  Rotations are continuous spring wheat (SW), SW-pea, SW-barley hay-pea, and SW-barley hay-corn-pea.  Ecological management practices vary by crop and are designed to improve competitiveness with weeds and snow capture.  After four years, the main effects of rotation and management system were significant for grain yield of SW and pea.  SW grain yield was greater in the two-year rotation with pea compared to continuous SW, but additional yield was not gained by planting SW every third or fourth year.  Continuous SW had the lowest reproductive tiller density.  Pea yield was 350 kg ha^-1 greater following barley or corn than spring wheat, primarily due to more pods m^-2.  Tillage system did not influence yield parameters of SW or pea.  Conversely, corn yield was 565 kg ha^-1 greater under zero- than conventional tillage.  Results from the first 4-year cycle of this long-term study document that diversified rotations improve spring wheat and pea yield, in part by increasing pod and reproductive tiller densities.