Influence of organic amendments on sorption and dissipation of imidacloprid in soil

The effect of organic amendments (OA) on imidacloprid sorption and dissipation in soil was investigated. A sandy soil was treated at a rate of 10% w/w with three OA: one liquid (Liquid Fertiormont, LF) and two solid (Solid Fertiormont, SF, and Alperujo, A). Sorption was measured using a batch equilibration method. Dissipation studies in the dark were performed by incubating pesticide-treated soils at moisture content of -0.33 KPa and 20+/-2degreesC for 28 days, whereas imidacloprid photolysis studies in soils were performed by irradiation of treated soils at water holding capacity in a Suntest apparatus with a xenon lamp for 32 h. In both cases, soils were sampled periodically and extracted for their imidacloprid content. Solid OA (SF and A) increased imidacloprid sorption by soils, whereas similar sorption was observed in soil amended with LF. Imidacloprid half-lives obtained from incubation studies in the dark remained unaffected upon amendment, whereas OA decreased the photolysis rate of imidacloprid in soils. However, no relation was observed between increase in sorption and decrease in the photodegradation rate of imidacloprid.