Dryland Organic Weed Management Strategies in Eastern Washington.

Weeds present the most formidable challenge to profitable organic farming in our region. Our conservation tillage cropping systems research was initiated in 2003. The most common weeds are wild oats, field bindweed, downy brome, and Canada thistle. Alfalfa, winter pea green manure, and winter wheat were the most successful crops for managing weeds in the first three years of the study; however, alfalfa and winter peas have been less successful in subsequent years. Winter wheat has been the most consistent competitive and profitable crop. Spring crops, especially spring peas, were less competitive with weeds, especially wild oats. Three conservation tillage implements have been utilized for weed management: rotary harrow (pre-plant), rotary hoe (in-crop), and undercutter sweep (pre-plant and post-harvest). We are also developing an experimental inter-row cultivator with a precision guidance system. Despite highly erosive soils, no significant runoff has been visible in our plots. Field bindweed is present in most plots and competitive winter cereals and the undercutter are the only management treatments; however, we have not seen a decline in bindweed infestations. Integration of competitive crops, rotations, seeding rates and conservation tillage are all necessary for weed management in these cropping systems.