The effect of formulation and moisture level on the persistence of carbofuran in a soil containing biological systems adapted to its degradation

Abstract

Abstract In a laboratory experiment in which soils were mixed frequently in an effort to maintain homogeniety, technical carbofuran was rapidly degraded to <5% of the initial application within 24 hr when applied to previously‐treated sandy loam maintained at 11.3 and 27.0% moisture. In previously‐untreated soil, >95% of the initial application remained after 24 hr but significant and variable loss was observed after 3 days (87–10% remaining). In contrast, there was no significant difference in the rate of disappearance of a granular formulation of carbofuran (Furadan® 15G) from previously‐treated and previously‐untreated soils when maintained at 11.3% moisture: Disappearance was relatively slow requiring 3 wk for ca. 90% decrease. When maintained at 27.0% moisture, the rate of disappearance of the granular formulation from the previously‐treated soil was significantly different from that in the previously‐untreated soil (eg. 2 vs 80% remaining at 7 days). The results demonstrate that an adapted soil microbial population is not the only factor to be considered in evaluating or estimating the persistence of field applied carbofuran. Key words: Pesticide disappearanceanti‐pesticide activityrapid degradation