CHEMICAL WEED-CONTROL OPTIONS FOR ZERO-TILLAGE SPRING BARLEY

The need for yearly applications of non-selective and postemergence he rbicides was evaluated in zero-tillage barley cropping systems in east ern Quebec. The effects of six glyphosate treatments, fall-applied, at several rates and frequencies, and four postemergence herbicide treat ments, on weed populations and crop yields, were measured over 2 yr in a zero-tillage spring barley monoculture. Yearly fall applications of glyphosate at rates at or above 0.5 kg a.i. ha(-1) combined with post emergence herbicide treatments controlled most weed groups and provide d optimum barley yields.