Impact of organic manures on the persistence of imidacloprid in the sandy clay loam soil of tropical sugarcane crop ecosystem

Impact of organic manures, viz., composted coir pith, press mud, sugarcane trash, and farmyard manure (FYM) on the persistence of imidacloprid in the sandy clay loam soil of tropical sugarcane crop ecosystem, was studied by employing rapid sample preparation method and reversed phase HPLC. The recoveries of the method employed to determine the residues of imidacloprid in the soil were in the range of 94.5 +/- 7.02-97.3 +/- 2.94% across the five levels of fortification ranged between 0.005 and 0.5 mu g/g. Imidacloprid was observed to persist in the soil manured with FYM and composted coir pith for 30 days with the half-life of 7.62 and 7.0 days, respectively as against 21 days with the half-life of 6.66 days in the non-manurial soil. The comparatively longer persistence of imidacloprid in the FYM and composted coir pith-applied soils was attributed to reduced leaching from the plow layer due to the adsorption of insecticide molecules by the added organic manures.