Rotation and Management Influence Spring Wheat Water Use and Yield.

Lack of diversification constrains dryland spring wheat (Triticum aestivum L.) production in the northern Great Plains.  We initiated a field study in 2004 comparing four crop rotations with each component present in a two-by-two matrix of tillage (conventional vs. zero tillage) and management (conventional vs. ecological) systems.  Rotations were continuous spring wheat (SW), SW-pea, SW-barley hay-pea, and SW-barley hay-corn-pea.  Ecological management practices varied by crop and were designed to improve snow capture and competitiveness with weeds.  Tillage system rarely influenced SW production.  Conversely, rotation and management system interacted with years.  Over six years, SW in diversified rotations typically had greater soil water content at planting, resulting in greater water use and 473 kg ha^-1 additional grain yield than continuous SW.  Conversely, ecologically managed SW averaged 644 kg ha^-1 less yield than conventionally managed SW.  Diversified rotations improved SW yield under semi-arid conditions.