Soybean (Glycine max) response to simulated drift from selected sulfonylurea herbicides, dicamba, glyphosate, and glufosinate

Field research was conducted to evaluate the response of soybean to various herbicides applied at rates to simulate drift damage. Dicamba, glyphosate, glufosinate, and the sulfonylurea herbicides CGA-152005, primisulfuron, ni cosulfuron, rimsulfuron plus thifensulfuron, and CGA-152005 plus primisulfu ron were applied to soybean at the two to three trifoliolate leaf stage in 1997 and 1998 at 1/100, 1/33, 1/10, and 1/3 of the recommended use rates. T he order of yield reduction after herbicide treatment was CGA-152005 > dica mba > CGA-152005 plus primisulfuron > rimsulfuron plus thifensulfuron > pri misulfuron. Soybean yields were not reduced by glyphosate, glufosinate, and nicosulfuron. Applications of all herbicides at rates higher than 1/33, of the use rate caused injury symptoms within 30 d after treatment. However, soybean plants had partially or fully recovered by the end of the growing s eason. Therefore, early-season injury symptoms from herbicide drift are not reliable indicators for soybean yield reduction.