Effect of preharvest applications of glyphosate on the drying, yield and quality of canola

Potential use of preharvest applications of glyphosate in canola (Brassica rapa L.) in western Canada both as a harvest aid and to control weeds promp ted this study. Experiments were conducted from 1988 to 1990 at four locati ons in the region to document the effectiveness of preharvest applications of glyphosate to enhance canola seed and foliage drydown and to measure the effect of such applications on seed yield and quality. Glyphosate was appl ied in early August to early September at rates of 0.45, 0.90 and 1.70 kg a cid equivalent ha(-1) to canola with seed moisture contents ranging from 79 to 12%. Seed and foliage moisture drydown were not enhanced by glyphosate treatment. Glyphosate treatments generally had little or no effect on canol a seed yields, seed weight, seed germination, green seed content or oil con tent except when applied when the pods were green and when seed moisture co ntents were high. Seed/pod moisture was not a reliable indicator of stage o f canola development and thus, should not be used alone as an indicator of when preharvest applications of glyphosate can be applied to canola without decreasing seed yield and quality.