Adsorption, Bioactivity, and Evaluation of Soil Tests for Alachlor, Acetochlor, and Metolachlor

Alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl) acetanilide], acetochlor [2-chloro-N-(ethoxymethyl)-6′-ethyl-o-acetotoluidide] and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] were adsorbed in similar amounts, approximately one-third that of the reference compound prometryn [2,4-bis(isopropylamino)-6-(methylthio)-s-triazine] by Ca-organic matter and seven soils. Adsorption isotherms for the four herbicides by Ca-montmorillonite were of the same shape, but different bonding mechanisms were involved. Adsorption and bioactivity of the acetanilide herbicides were correlated with organic matter, clay content, and other soil parameters as determined by two different soil- testing laboratories.