A review on the enhanced degradation of pesticides in tropical agricultural soils

Pesticides newly introduced into the soil are normally poorly degraded by the native soil microbes. However, studies have demonstrated that repeated pesticide exposure to the soil microbes potentially enhances their biodegradation through selective enrichment of the pesticide-metabolizing microorganisms, particularly when the compound is used as a C or N and energy source. Enhanced degradation of recalcitrant compounds in soil has a significant environmental impact as the chemicals are less likely to contaminate the environmental ecosystems. We have undertaken several studies to isolate these adapted microbes which rapidly degrade chemicals hitherto known to be recalcitrant in soil. These microbes could potentially be used for bioremediation (bioaugmentation). In addition, other studies have shown the potential to remove pesticide contamination from the environment by use of organic materials locally generated as organic amendments (biostimulation). In this review, the various methods used in the course of our studies in determining the utilization of the selected chemicals (pesticides) by the adapted microbes as a source of C and N for growth and energy are discussed. We also present some of the compounds we have worked with and the successes registered in isolating key degraders of the respective pesticides and the extent the locally generated organic materials are able to enhance the degradation of the respective chemicals in soil.