A Lysimeter Study of Grass Cover and Water Table Depth Effects on Pesticide Residues in Drainage Water

Abstract

A study was undertaken to investigate the effect of soil and grass cover, when integrated with water table management (subsurface drainage and controlled drainage), in reducing herbicide residues in agricultural drainage water. Twelve PVC lysimeters, 1 m long and 450 mm diameter, were packed with a sandy soil and used to study the following four treatments: subsurface drainage, controlled drainage, grass (sod) cover, and bare soil. Contaminated water containing atrazine, metolachlor, and metribuzin residues was applied to the lysimeters and samples of drain effluent were collected. Significant reductions in pesticide concentrations were found in all treatments. In the first year, herbicide levels were reduced significantly (1% level), from an average of 250 mg/L to less than 10 mg/L. In the second year, polluted water of 50 mg/L, which is considered more realistic and reasonable in natural drainage waters, was applied to the lysimeters and herbicide residues in the drainage waters were reduced to less than 1 mg/L. The subsurface drainage lysimeters covered with grass were found to be the most effective treatment system.