Effect of Soil Cultivation, Soil Surface and Water on the Persistence of Insecticidal Residues in Soils1

Abstract

Since relatively large amounts of water evaporate yearly from soils, experiments were conducted to obtain more information on the relationship between this water loss and the persistence of residues of insecticides in various soil types. The effect of soil stirring on the persistence of aldrin and DDT residues was also investigated. It was found that the persistence of aldrin is affected by soil moisture. water, apparently, causes a displacement of the aldrin from the soil particles. once this is accomplished, a major part of the insecticide is lost by volatilization. Aldrin is lost from water surfaces, hut this loss does not seem to be affected by water evaporation as such. The persistence of DDT was not affected by the amounts of water evaporated from soils or glass surfaces, or by enlargement of surfaces onto which DDT had been deposited. Under field conditions, however, daily disking of a loam soil treated with aldrin or DDT at 4 Ib./5" acre caused a reduction of 38% of the aldrin residues and 25% of the DDT residues, during a 3-month period. Frequent soil disking could possibly serve as a method for reducing the residue level of volatile insecticides in soils.