Impact of animal waste lagoon effluents on chlorpyrifos degradation in soils

Animal‐derived lagoon effluents are a good source of inorganic nutrients and organic matter; however, they may impact the degradation and transport of soil‐applied pesticides. The degradation of chlorpyrifos in poultry‐, swine‐, and cow‐derived effluents and effluent‐soil matrices were studied using batch and column incubation studies. Chlorpyrifos was degraded by aerobic microbial processes in animal‐derived lagoon effluents. Microbial community analysis by denaturing gradient gel electrophoresis of polymerase chain reaction‐amplified 16S ribosomal ribonucleic acid genes showed that a single band became dominant in effluent during chlorpyrifos degradation. In soils, both biotic and abiotic degradation contributed significantly to the overall dissipation of chlorpyrifos. Large differences in degradation rates were observed between soils, with the fastest rate observed in soil with higher pH and cation‐exchange capacity. Effluents appeared to have only a minor effect on chlorpyrifos degradation in soils, although effluent‐induced increases in soil‐solution pH over time may enhance hydrolysis by a few percent in low‐pH soils. Soil properties, not effluent properties, appear to control chlorpyrifos degradation under laboratory conditions; however, the impact on changes in soil properties and microbial ecology with long‐term effluent irrigation warrants further investigation.