Environmental factors influencing effects of chemicals on soil animals : studies at population and community levels

Abstract

Effects of abiotic environmental factors like soil organic matter content, soil moisture and temperature on the toxicity of chemicals to soil animals were studied in laboratory experiments. An insecticide, dimethoate, and two fungicides, benomyl and propiconazole, were used as reference chemicals in the experiments. Two types of experiments were conducted: single species tests and microcosm experiments. Single species experiments revealed that soil organic matter content affects substantially the toxicity of dimethoate to collembolans. Increasing organic matter content decreased dimethoate concentration in the soil pore water, and hence its toxicity. Lowering the temperature increased the toxic effects, but only slightly. Population level effects lasted longer at low temperature due to slower reproduction of collembolans. Decreasing the soil moisture either decreased (dimethoate) or increased (benomyl) the toxic effects on an enchytraeid worm. In the microcosm experiments pesticide application and drought decreased different soil animal groups resulting in lower total soil animal numbers than exposured to either of these stressors alone. Both fungicides had only minor effects on soil animal communities and soil processes, possibly due to relative low significance of fungal based energy channel in agricultural soil. It was revealed that both single species tests and microcosm experiments are needed when assessing ecotoxicological effects of chemicals in the environment.