Effects of agricultural practices on the binding and fate of 14C-parathion in soil

Abstract

Abstract The effects of agricultural practices on the formation of unextractable, bound residues of 14C‐(ring)‐parathion in a Piano silt loam soil were investigated. Relative binding of 14C‐parathion in soil decreased with increasing application rates of the insecticide. Thus, with a 1 ppm application rate, 31% of the initially applied radiocarbon was bound after 4 weeks, while binding at application rates of 10 and 45 ppm amounted to only 22% and 17% of the applied dose, respectively. This decreased binding at higher application rates resulted in an increased persistence of extractable 14C‐parathion residues. Binding of 14C‐parathion in soil was also greater after the insecticide had been uniformly mixed with the soil than when it was applied to the soil surface. Thus, an application of 14C‐parathion at 15 ppm resulted in 27% binding after 4 weeks when uniformly mixed with the soil, but only 20% when applied to the soil surface. With both the mixed and the surface applications, more binding of 14C‐parath...