Intercropping Peas and Small Grains during the Transition Period to Organic Production.

Organic farming in the dryland agriculture region of eastern Washington is rare, and little information exists for growers to make a successful transition from conventional to organic production. The three-year transition period is an important time to build up soil fertility; however, sources of manure or compost are not available in many areas, and transportation costs are often prohibitive. In this case, growers must utilize green manure for soil improvement and sacrifice a year or more of profit in exchange for potentially higher yields in later years. The necessity of growing green manure crops increases costs and lowers returns for growers, serving as a disincentive to adopt organic practices. Intercropping grain and a green manure crops has the potential to build soil fertility without sacrificing all grain production. In this study, spring wheat, a forage triticale variety, and a grain triticale variety were planted in alternating rows with field peas, which were mown down at flowering to serve as a green manure soil input. Monocropped spring wheat and grain triticale yielded 4650 kg ha^-1 and 4500 kg ha^-1, respectively, under certified organic production. While grains intercropped with peas were planted to 50% of the area of monocropped grains, intercropping only reduced spring wheat and triticale grain yields by 40%. Grain nitrogen content was greater in intercropped versus monocropped grain, especially in spring wheat. Intercropping also provided weed control benefits in spring wheat, reducing weed biomass by 55%; however, no differences in weed biomass were observed between treatments in either triticale variety. The technique of intercropping grains and green manure has the potential to reduce weed pressure during the transition period to organic, as well as provide some revenue to growers during a usually unprofitable period.