2007 Annual Report 1a.Objectives (from AD-416) This research project objective is to assess the effects of weed management and conservation practices on soil biological, chemical, and physical properties under Mississippi Delta conditions. This will provide an understanding of the interactions between alteration of soil properties by crop and weed management practices and their influence on herbicide fate. This information will be used to develop strategies to both improve herbicide efficacy and reduce the environmental impact of herbicide use. 1b.Approach (from AD-416) Assessment of weed and conservation practices on the environmental fate of herbicides in soil and plant residues will be assessed in laboratory, greenhouse and field conditions. Most field investigations will study long-term changes in soil properties associated with reduced tillage, cover crops, and residue management to determine how suites of best management practices can be developed to facilitate herbicide effectiveness with minimal potential for adverse effects on the environment. Edge-of-field practices such as filter strips will be assessed to make recommendations on the most effective materials for removal and processing of herbicide contaminants. Field and laboratory research on the environmental fate of the herbicide s-metolachlor will be part of a national effort to examine the role of edaphic factors in degradation kinetics of this herbicide to develop into a predictive model for ascertaining herbicide efficacy and minimize environmental risks. Factors associated with herbicide dissipation, e.g., herbicide degradation, sorption and movement, and specific microbial degradation pathways, will be studied to determine interactions among weed management practices and the environmental fate of herbicides. The effects of using transgenic crops resistant to the herbicides glyphosate and glufosinate on soil microflora and plant-microbial interactions will be evaluated, specifically nitrogen fixation and nitrogen assimilation. The ecology of soil microflora and associated microbial processes will be studied in legume cover crop systems for cotton and flooding systems for a rice soybean rotation. 3.Progress Report None 4.Accomplishments Atrazine degradation/mineralization to carbon dioxide in a Mississippi soil developed within one year of atrazine application. Alternate rotation of corn with cotton did not impede the development of enhanced atrazine degradation. The biological basis of atrazine degradation was demonstrated by loss of activity following autoclaving and isolation of bacterial strains capable of complete metabolism of atrazine to carbon dioxide. Greenhouse studies indicated that accelerated atrazine degradation can reduce herbicidal efficacy in controlling broadleaf weeds. The potential for loss of weed control due to accelerated atrazine degradation is of concern to growers in the Mid South and other areas of the U.S. Planting soybean in narrow rows rather than wide rows reduces surface runoff losses of the herbicide metolachlor. Greater herbicide absorption by the soybean canopy coupled with higher water use in the narrow row cropping system combined to reduce the pesticide’s transport potential. The results indicate that planting soybean in narrow rows can reduce herbicide transport thereby protecting surface water quality. This is a significant advance since producers are rapidly adopting narrow-row cropping systems. The cotton herbicide fluometuron and its metabolite desmethyl fluometuron degraded more rapidly in reduced tillage soils compared to a no-tilled soil. However, sorption (binding) of fluometuron and its metabolites was greatest in no-tilled soils. The increased persistence of fluometuron in no-tillage soils is limited by availability to soil microbes for degradation. With broad adoption of transgenic herbicide resistant soybeans, the herbicide, glyphosate, is an important tool for weed management in soybeans. A series of field and laboratory experiments assessed the effect this herbicide has on soil microorganisms using fatty acid methl ester (FAME) techniques. In two years of field evaluation no significant effects of glyphosate were detected on soil or root microbial communities after two in-season glyphosate applications. Exposure of soils to glyphosate in a laboratory experiment resulted in small, short-term changes in the microbial community and a brief inhibition of microbial activity. Likewise in laboratory studies, glyphosate did not persist in the soil due to a moderate rate of microbial mineralization of this herbicide and formation of bound residues. 5.Significant Activities that Support Special Target Populations None 6.Technology Transfer Number of invention disclosures submitted 2 Number of web sites managed 2 Number of non-peer reviewed presentations and proceedings 17 Number of newspaper articles and other presentations for non-science audiences 1 Review Publications Matocha, M.A., Krutz, L.J., Senseman, S.A., Koger III, C.H., Reddy, K.N., Palmer, E.W. 2006. Spray carrier ph effect on absorption and translocation of trifloxysulfuron in palmer amaranth (amaranthus palmer) and texasweed (caperonia palustris). Weed Science 54:969-973. Zablotowicz, R.M., Locke, M.A., Krutz, L.J., Lerch, R.N., Lizotte Jr, R.E., Knight, S.S., Gordon, R.E., Steinriede Jr, R.W. 2006. Influence of watershed system management on herbicide concentrations in mississippi delta oxbow lakes. Science of the Total Environment 370:552-560. Zablotowicz, R.M., Krutz, L.J., Reddy, K.N., Weaver, M.A., Koger III, C.H., Locke, M.A. 2007. Rapid development of enhanced atrazine degradation in a dundee silt loam soil under continuous corn and in rotation with cotton. Journal of Agricultural and Food Chemistry, Vol. 55, Number 3, pp. 852-859. Krutz, L.J., Koger III, C.H., Locke, M.A., Steinriede Jr, R.W. 2007. Reduced Surface Runoff Losses of Metolachlor in Narrow Row Compared to Wide-Row Soybean. Journal of Environmental Quality 36:1331-1337. doi:10.2134/jeq2006.0548. Locke, M.A., Zablotowicz, R.M., Steinriede Jr, R.W., Kingery, W.L. 2007. Degradation and sorption of fluometuron and metabolites in conservation tillage soils. Journal of Agricultural and Food Chemistry. 55:844-851. Weaver, M.A., Krutz, L.J., Zablotowicz, R.M., Reddy, K.N. 2007. Effects of glyphosate on soil microbial communities and its mineralization in a mississippi soil. Pest Management Science 63:388-393. Krutz, L.J., R.M. Zablotowicz, K.N. Reddy, C.H. Koger III, and M.A. Weaver. 2007. Enhanced degradation of atrazine under field conditions correlates with a loss of weed control in the glasshouse. Pest Management and Science 63:23-31. Krutz, L.J., R.M. Zablotowicz, K.N. Reddy, C.H. Koger III, and M.A. Weaver. 2007. Enhanced degradation of atrazine under field conditions correlates with loss of weed control in the greenhouse. Pest Management Science 63:23-31.