EFFICACY OF DOWNY BROME HERBICIDES AS INFLUENCED BY SOIL PROPERTIES

Controlled environment experiments were conducted to determine the eff ect of various edaphic factors on the efficacy of metribuzin, BAY SMY 1500, cinmethylin, and napropamide to control downy brome (Bromus tect orum L.). Experiment 1 determined the effects of soil organic matter, pH and texture and experiment 2 determined the effect of soil water co ntents ranging from -0.03 to -1.5 MPa on herbicide efficacy on downy b rome. Metribuzin, BAY SMY 1500, cinmethylin, and napropamide efficacy on downy brome was highly correlated with soil organic matter and soil water content. Phytotoxicity of these herbicides was decreased up to two- to threefold as organic matter increased and soil water content d ecreased. Metribuzin and BAY SMY 1500 efficacy on downy brome increase d as soil pH increased. Cinmethylin was more efficacious in sandy soil s. This information may aid in determination of precise herbicide rate s for various soil types to allow growers to achieve consistent contro l of downy brome without injuring winter cereals.