Mature yard waste compost was mixed with pesticide-contaminated soil obtained from an agrichemical retail dealership to determine how much compost was needed to significantly stimulate plant growth, microbial activity, and pesticide degradation. The soil initially contained 1.6 mg kg-1 trifluralin, 1.7 mg kg-1 metolachlor, and 2.0 mg kg-1 pendimethalin. Proportions of the mixes were 0, 1, 5, 10, 20 and 40% compost (w/w). Mixtures were planted with sweet corn (Zea mays) and placed in a greenhouse for 4 weeks. Plant dry matter production, microbial activity (dehydrogenase), and pesticide content were determined. Maximal stimulation of plant growth was found at 20% compost, at which amount, plant growth was 154% of growth in only contaminated soil. Significant increases in soil dehydrogenase were seen at 20% and 40% compost with the activity being 18.8 times higher than it was in only contaminated soil. The soil was inhibitory to microbial activity at all rates of compost addition, with no stimulation in microbial activity at <20% compost. Degradation of trifluralin and pendamethalin was increased at compost rates of 20% or more. Only 40% compost significantly stimulated metolachlor degradation. Percentage degradation of the pesticides after 4 weeks of greenhouse incubation and 16 weeks of laboratory degradation was 85% (trifluralin), 100% (metolachlor), and 79% (pendimethalin). The results indicate that addition of relatively large amounts of compost to soils with phytotoxic and antimicrobial properties can significantly improve prospects for successful remediation, but smaller amounts have no significant benefit.
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- Minimum Effective Compost Addition for Remediation of Pesticide-Contaminated Soil
Michael A. Cole
- Springer Netherlands