Metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] has considerable potential for yellow nutsedge (Cyperus esculentus L.) control in crops commonly produced in the Texas High Plains. Little information is available, however, concerning adsorption characteristics of metolachlor in soils of this region. Adsorption and movement of metolachlor were determined in three commonly occurring soils of the Texas High Plains. Organic carbon contents of the soils by weight varied from 0.3 to 0.5%, and the clay fraction ranged from 16 to 33%. Freundlich adsorption isotherms exhibited two linear regions for each soil, suggesting the possibility of multilayer adsorption. K′oc values and coefficients of determination for organic carbon and clay content vs. Freundlich K values indicated that organic matter was the predominant adsorbent for metolachlor in the soils studied. Desorption, soil column leaching, and thin-layer plate studies demonstrated metolachlor to be sufficiently mobile in scils low in organic matter to cause possible crop injury or loss of efficacy.

Field studies in 1978 and 1979 evaluated the effectiveness of single and combination herbicide treatments in processing peas (Pisum sativum L.) and soybeans [Glycine max (L.) Merr.] for the control of wild proso millet (Panicum miliaceum L.). Eight treatments that included dinitroaniline herbicides controlled wild proso millet adequately through the entire growing season of the early-planted peas (approximately 60 days). Wild proso millet emergence and growth in untreated peas was suppressed by the early emergence, rapid growth, and high plant density of the drill-planted crop. Trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) at 0.8 kg/ha stunted pea growth and was the only treatment that reduced yields significantly. No herbicide treatment evaluated in soybeans controlled wild proso millet adequately for the entire growing season without reducing soybean growth and yield. Treatments containing dinitroaniline herbicides, which controlled wild proso millet in peas and resulted in good yield, did not perform similarly in soybeans.