Sorption and leaching of three nonfumigant nematicides in soils

Abstract

Sorption and leaching of three nonfumigant nematicides (aldicarb, oxamyl, and fenamiphos) were studied using three U.S. soils (Arredondo sand, Cecil sandy loam, and Webster silty clay loam). Equilibrium sorption coefficient (K) values, measured using the batch‐slurry technique, were in the order: aldicarb ? oxamyl « fenamiphos. Nematicide mobilities measured in soil columns during water infiltration were in the order: aldicarb ? oxamyl « fenamiphos. This order was as anticipated from the K values. Leaching of aldicarb was also measured in a field microplot of Arredondo sand. Rapid leaching of aldicarb along with the infiltrating water, similar to that noted in packed soil columns, was observed.

Data from the soil column and field leaching studies were used to evaluate a simple piston displacement model. The model accurately predicted the position of the wetting fronts, but underpredicted nematicide leaching. Analysis of the soil column data revealed that nematicide K values measured by the batch technique need to be adjusted by a factor of about 0.4 to accurately predict nematicide leaching in soil columns and a field microplot. The value of this factor was invariant with the soil‐pesticide combination. The need for this adjustment factor and its applicability to other soils and pesticides needs to be carefully evaluated.

Key words:

• aldicarb
• oxamyl
• fenamiphos
• sorption nonequilibrium
• piston‐displacement model
• ground water pollution