Soil amidase activity in polyacrylamide-treated soils and potential activity toward common amide-containing pesticides

Polyacrylamide (PAM) is currently used as an irrigation water additive to s ignificantly reduce the amount of soil erosion that occurs during furrow ir rigation of crops. Elevated soil amidase activity specific toward the large PAM polymer has been reported in PAM-treated field soils; the substrate sp ecificity of the induced amidase is uncertain. PAM-treated and untreated so ils were assayed for their capacity to hydrolyze the amide bond in carbaryl (Sevin), diphenamid (Dymid), and naphthalene acetamide. Based on results o btained with a soil amidase assay, there was no difference between PAM-trea ted and untreated soils with respect to the rate of amide bond hydrolysis o f any of the agrochemicals tested. It appears that under these assay condit ions the PAM-induced soil amidase is not active toward the amide bonds with in these molecules. However, carbaryl was hydrolyzed by a different soil am idase. To our knowledge, this is the first soil enzyme assay-based demonstr ation of the hydrolysis of carbaryl by a soil amidase.