Degradation of Three Acetanilide Herbicides in Soil

Abstract

The persistence of alachlor [2-chloro-2′,6′-diethyl- N -(methoxymethyl) acetanilide], metolachlor [2-chloro- N -(2-ethyl-6-methylphenyl)- N -(2-methoxy-1-methylethyl)acetamide], and propachlor (2-chloro- N -isopropylacetanilide) in soil was examined under laboratory and field conditions using sorghum ( Sorghum vulgare Pers. ‘NB280S′) or annual ryegrass ( Lolium multiflorum Lam.) as bioassay species. In laboratory studies, degradation rate of alachlor and propachlor was greater at 50 and 80% than at 20% field capacity at 20 C. Degradation of metolachlor was greater at 80 than at 20% field capacity. Degradation rate of alachlor and metolachlor at 50% field capacity was greater at higher temperatures. Propachlor degradation rate varied with temperature. Under irrigated, cropped field conditions, the order of persistence was metolachlor > alachlor > > propachlor.