Influence of Soil Treatment on Persistence of Six Chlorinated Hydrocarbon Insecticides in the Field

Abstract

AbstractAn experiment was designed to compare the rate of disappearance of dieldrin, endrin, heptachlor, lindane, DDD, and DDT from flooded and nonflooded soils. Chopped alfalfa (Medicago sativa L.) (0.25% in the top 10 cm of soil) was added to half of the plots. The nonflooded treatment was subdivided into a soil mixing treatment (surface 8 cm of soil mixed every 2 weeks) and a nonmixing treatment. Holes were dug in the field and plastic containers (43 cm in diameter and 53 cm in depth) were placed in the holes and filled with soil to a depth of 48 cm so that the soil surface inside the container was level with the surrounding soil. Pesticides were incorporated into the surface 10 cm of soil. In the nonflooded soil, neither soil mixing nor added alfalfa enhanced the loss of dieldrin, endrin, DDD, or DDT from the top 8 cm of soil during a 22‐week period. Under the same conditions, the concentrations of lindane and heptachlor decreased with time, and more pesticide was lost from the soil receiving the mixing treatment than from the nonmixed soil. Lindane, heptachlor, endrin, and DDT were susceptible to degradation in the flooded soils. The order of degradation for the degradable insecticides was heptachlor > DDT > lindane > endrin.