TRANSPORT MECHANISM IN SOIL: METABOLISM AND MOVEMENT OF INSECTICIDES FROM SOILS INTO WATER AND CROP PLANTS

Abstract

The persistence, movement and metabolism of insecticides in soils are affected by various environmental conditions. Field data are presented, showing that phorate—after granular band application—moved in both horizontal and vertical directions. Phorate sulphone was the major metabolite recovered. The metabolism and persistence of this insecticide was also affected by its mode of application. Utilizing a soil-plant-water ecosystem, it was demonstrated that the percolation of water through this system did not affect the movement of [14C]-phorate through loam soils, but did so with soils of lesser or no sorptive capacity. Water percolated through agricultural soils contained phorate metabolites (phorate sulphoxide and phorate sulphone), while corn greens grown in this system contained in addition phoratoxon sulphoxide and phoratoxon sulphone. With [14C]-Dyfonate it was shown that the insecticide did not move to an appreciable extent through an agricultural loam soil and its transport with water through soils was, to a large extent, a function of the soil type. Detergents, having increased the persistence of parathion in soil, indirectly increased the amount of parathion within the percolated water. The presence of salts prevented the appearance of aldrin residues in percolated water and reduced the amount of parathion residues. Movement of insecticides from soils into plants was shown to be dependent on energy supply systems of root cells, soil nutrients and soil insecticide concentrations.