Effects of Harvest-Aid Herbicides on Soybean (Glycine max) Seed Yield and Quality

Abstract

Experiments were conducted in 1989 and 1990 to investigate the influence of 220 g ai ha–1 AC 263,222, 840 g ai ha-4 glufosinate, 560 g ai ha–1 glyphosate, and 840 g ai ha–1 paraquat applied at R5, R6, R7, and R8 soybean growth stages as harvest-aid treatments on soybean seed quality. Soybean yield was severely reduced by all herbicides applied at R5. Only paraquat and glufosinate reduced soybean yield when applied at R6, and none of the herbicides reduced yield when applied at R7 or R8. Paraquat and glufosinate reduced seed weight when applied at RS and R6. Glyphosate and AC 263,222 reduced seed germination when applied at RS, R6, and R7 growth stages, and normal seedling percentages were also reduced by glyphosate at these growth stages. Glufosinate and AC 263,222 affected normal seedlings only at R5 and R6. Soybean hypocotyl and primary root lengths were reduced by glyphosate and AC 263,222 applications at R5 and R6, whereas glufosinate and paraquat did not affect these variables. Glyphosate applied at R5 reduced shoot weight in 1-mo-old soybean plants. No effects were observed on soybean yield, seed germination or seedling development when herbicides were applied at R8.