Dinitroaniline herbicide carry over to sugarbeet

Abstract

A fo ur-year fi eld experiment was conducted near Scotts­ bluff, NE to compare degradation of ethalfluralin, pen­ dimethalin, and trifl uralin in soil. Dinitroaniline herbicides were applied at rates of0.56, 1.12, and 2.24 kg/ha preplant incorporated before planting dry edible bean. Herbicide degradation was monitored by chemical extraction and gas chromatography. Sugarbeet followed dry edible bean in the crop rotation and crop growth was related to dinitroaniline herbicide concentrations in soil. Moldboard plowing of the soil before sugarbeet planting reduced dinitroaniline her­ bicide concentration in the upper 0 to 8 cm of the soil pro: file by 39 and 76010 in 1990 and 1992, respectively. Plowing increased the concentration of herbicide in the 15 to 30 cm zone of the soil profile. Ethalfluralin degraded more rapid~ Iy than pendimethalin or trifluralin. Eleven months after herbicide application, residues of 0.07 mg/kg or greater of pendimethaJin or trifluralin in the upper 0 to 8 cm of the profile reduced sugarbeet growth and stand.