Efficacy of downy brome herbicides as influenced by soil properties

Controlled environment experiments were conducted to determine the effect of various edaphic factors on the efficacy of metribuzin, BAY SMY 1500, cinmethylin, and napropamide to control downy brome (Bromus tectorum L.). Experiment 1 determined the effects of soil organic matter, pH and texture and experiment 2 determined the effect of soil water contents ranging from −0.03 to −1.5 MPa on herbicide efficacy on downy brome. 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 decreased. Metribuzin and BAY SMY 1500 efficacy on downy brome increased as soil pH increased. Cinmethylin was more efficacious in sandy soils. This information may aid in determination of precise herbicide rates for various soil types to allow growers to achieve consistent control of downy brome without injuring winter...