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

Abstract

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 ± 2°C 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.

Keywords:

• Imidacloprid
• Soils
• Organic amendments
• Sorption
• Dissipation
• Photodegradation

Acknowledgements

This work has been partially financed by the Project AGL 2001-1554 from the Ministry of Science and Technology of Spain and Research Group RNM 124 of Junta de Andalucía.