| Rhizodegradation is a process by which plant-supplied substrates stimulate soil microbial communities in plant root zones (rhizospheres) to cause removal of undesirable levels of contaminants in soil. Dissipation of the synthetic pyrethroid insecticide, bifenthrin was examined in two soil types under rhizosphere influences of alfalfa (Medicago sativa), big bluestem ( Andropogon gerardii), and switchgrass (Panicum virgatum) to understand components and processes that are involved in removal of unwanted levels of the insecticide from soil. The two soils examined were Armour silt loam collected at Tennessee State University agricultural experimental station in Nashville TN, and Sullivan sandy loam collected from Tennessee Technological University agricultural station in Cookeville TN. After 10 weeks in soils, significantly more bifenthrin was recovered from both unplanted soil types than recoveries in planted soils. Different levels of bifenthrin were recovered in planted Armour soil but the levels were not significantly different. Recoveries of bifenthrin in planted Sullivan soil were different but in contrast to observation in Armour soil, differences in bifenthrin recoveries from planted Sullivan soil were statistically significant. We are using traditional microbial enumeration methods (Plate Dilution Frequency Assay) and Biolog carbon substrate utilization profiling to relate bifenthrin dissipation to microbial communities so rhizodegradation may be developed further for routine clean up soils that have been negatively impacted by bifenthrin and potentially other synthetic pyrethroids. |
