WEED MANAGEMENT FOR CROP PRODUCTION IN THE NORTHWEST WHEAT (TRITICUM-AESTIVUM) REGION

A 9-yr large-scale integrated pest management (IPM) study was initiate d in 1985 to develop and refine profitable conservation cropping syste ms in the Palouse wheat-growing region of the Pacific Northwest, Weed scientists from the USDA-ARS and the land-grant universities of ID and WA led a team of researchers and extension personnel from eight disci plines to investigate the interactions of crop systems, tillage system s, and weed management levels (WR;LL) on crop production, Ineffective weed control has been a major deterrent to the adoption of conservatio n tillage by wheat growers, With this in mind, the primary focus of th e scientists on the IPM project was integrated weed management (IWM) i n conservation crop production systems for highly erodible land, For t he first time in the Pacific Northwest, systems research developed a c onservation production system using a 3-yr crop rotation that controll ed weeds effectively, reduced erosion, was less risky than traditional farming systems, and was profitable, Broadleaf weeds were more preval ent in the 3-yr rotation of winter wheat-spring barley-spring pea comp ared to continuous wheat in both conservation and conventional tillage systems, In conservation tillage, troublesome grass weeds included wi ld oat and downy brome, Wild oat was controlled effectively at the mod erate and maximum weed management levels under conservation tillage in the 3-yr rotation, Two years out of winter wheat (such as in the 3-yr rotation) reduced downy brome populations, In contrast, growing a spr ing crop 1 yr, followed by 2 yr of winter wheat was not effective for controlling downy brome. Effective weed control was instrumental in de veloping successful conservation IPM cropping systems, and education a nd technology transfer were important in helping action agencies assis t growers in adopting these systems.