Effect of post-emergence herbicide injury and planting date on yield of narrow-row soybean (Glycine max)

Abstract

Some herbicides used post-emergence (POST) in soybean production cause foliar injury; however, new growth is normal and the crop does not appear to be further affected. Experiments were conducted to determine the effect of different levels of foliar injury caused by POST herbicides on yield of soybean cv. Maple Glen when planted early and late in a weed-free environment. Level of foliar injury was variable from year to year. Aciflurofen and imazethapyr caused foliar injury of 7 to 35% whereas, thifensulfuron and bentazon gave foliar injury ranging from 0 to 20% at 15 d after treatment (DAT). Foliar injury was short lived, and by 30 DAT had disappeared in 1994 and 1997, but still was visible at 11% for aciflurofen and 17% with imazethapyr on late-planted soybean in 1995. Aciflurofen- and imazethapyr-treated soybeans were still stunted at 30 and 60 DAT. Only imazethapyr reduced yields on both early- and late-planted soybean, in the 3 yr of the study. Yield of Maple Glen soybean was higher with early-planted soybean than with late-planted soybean in all years. Maximum yields were obtained in control plots kept weed free all season by a pre-emergence application of metribuzin. Key words: Aciflurofen; bentazon; imazethapyr; metribuzin; thifensulfuron; stunting; delayed maturity; foliar injury