Asuming-Brempong, S., S.J. Flynn and J.M. Tiedje
Presented at the All Scientist Meeting (1996-07-16 to 1996-07-17 )
2,4-dichlorophenoxyacetic acid (2,4-D) is a herbicide which can be degraded by soil microbes. Application of high rates of 2,4-D leads to a shift in microbial community structure. We are using various KBS soils enriched for 2,4-D degrading bacteria as a model of bacterial community structure to address the role of environment, agricultural methods and physio-chemical properties of soils. Soils from LTER treatments one, two and eight as well as soils from the coniferous, deciduous and successional forest plots were sampled and used to initiate microcosm studies. The microcosms were treated with 100 ppm 2,4_D and incubated at 25 öC. By two weeks the 2,4-D concentration in many of the microcosms had been reduced to 50 ppm. Once these microcosms have degraded 2,4-D to a level below 10 ppm 2,4-D will be reapplied at a concentration of 100 ppm. Community analysis studies based upon bacterial 16S rRNA genes will be performed once individual microcosms have degraded three applications of 100 ppm 2,4-D to below 10 ppm 2,4-D.Another portion of this project is to determine the effect of application of 2,4-D at a high rate (100 ppm) in the field. We are examining previously treated plots in the gene transfer study area that have a shift in their microbial community structure to determine the effect upon nutrient cycling by this altered community. We are also examining the effect of termination of 2,4-D treatment on this 2,4-D enriched microbial community.
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