Alternative Strategies for Transitioning to Organic Production in Direct-Seeded Grain Systems in Eastern Washington I: Crop Agronomy

Abstract

Organic grain production is not common to eastern Washington, but offers attractive market opportunities if systems can be developed that are compatible with regional production constraints. Erodible soils make tillage-intensive systems unsustainable, and there are limited alternative fertility options. Given these constraints, the objective of this study was to evaluate nine cropping systems during the transition to organic grain production under reduced tillage and relying on legumes as the primary source of crop nitrogen. The experimental transition systems ranged in the degree in which legume grain crops or legume green manures/forages were present in the rotation. We found that spring pea grown for grain to be a poor choice for organic production due to the susceptibility of this crop to insect pests and weeds, which generally resulted in crop failure. Likewise, bell bean was poorly suited as a legume green manure crop due to its low productivity in our region. In contrast, alfalfa and winter pea-based systems achieved the best legume biomass production, weed suppression, and crop yields in the subsequent crops. Winter wheat substantially out-yielded spring wheat, but the yields of both of these crops were well below the yield potential typically achieved under conventional production. Competition from annual weeds, such as wild oat and prickly lettuce, and the perennial weed field bindweed was difficult to manage under the reduced tillage regimes employed in this study.