2007 Annual Report 1a.Objectives (from AD-416) Develop an increased understanding of soil microbial ecology and how soil microbial communities may be managed to increase agricultural sustainability and improve soil quality. Develop improved methods including FAME analysis and PCR primers to assess soil and rhizosphere microbiological communities. Determine the effects of soil properties such as texture, pH, organic matter, aggregation, and mineralogy on soil and rhizosphere microbial community structure. 1b.Approach (from AD-416) Develop fast and sensitive methods for fatty acid analysis in order to identify single colonies of cultured bacteria and identify fatty acids of microbial origin in environmental samples. Develop new PCR primers to microbes that are widely distributed in soil but not generally cultivable, including Acidobacteria, Verrucomicrobia, and Archaebacteria. ARS scientists across USA collect soils varying widely in soil type and management system. Subsamples sent to participating labs for analysis. Analyze microbial community structure by PLFA and T-RFLP. In laboratory experiments soils amended with silica particles to alter texture, incubated with wheat straw, and microbial community structure analyzed. Soils incubated at various temperatures and water potentials and microbial community structure analyzed. Soils amended with different types and quantities of organic matter and microbial community structure analyzed. 3.Progress Report A new method for preparing fatty acid derivatives was developed. These fatty acid esters are detected at high sensitivity by gas chromatography using an electron capture detector. This method may be useful for detecting and identifying very small quantities of bacteria. Samples taken from the second year of a field experiment on plasticulture and cover cropping in tomato production were analyzed for soil and rhizosphere microbial community structure. Results were similar to the results from the first year of the experiment, and indicate that soil moisture may be more important than soil temperature in producing differences in soil microbial community structure when comparing plasticulture to cover cropped agroecosystems. Cover cropping resulted in increased microbial biomass. We continued to analyze soil samples taken from fields containing Bt and non-Bt corn for microbial community structure. Soil DNA extracts were prepared and analyzed. Availability of two of the most biologically-active chemicals from rye cover crops, DIBOA and BOA, were analyzed in soil systems. DIBOA and BOA were mixed (1 to. 5)in a soil/water solution and the presence of the chemicals in each phase was monitored by sampling and analysis using liquid chromatography mass spectrometry at spaced intervals over a 24 hour period. The loam soil, with the highest amount of organic matter, bound the greatest proportion of the available DIBOA and the silt loam and loamy sand bound a smaller percentage of DIBOA than the loam soil but behaved similarly to each other. Knowing the relative availability of these biologically-active chemicals in the soil environment is important when applying different management practices during cover cropping, for example, matching the amount of incorporated rye cover crop with soil properties to maximize effects on weed suppression or nematode fecundity. 4.Accomplishments None 5.Significant Activities that Support Special Target Populations None 6.Technology Transfer Number of non-peer reviewed presentations and proceedings 5 Number of newspaper articles and other presentations for non-science audiences 3 Review Publications Blackwood, C.B., Buyer, J.S. 2007. Evaluating the physical capture method of terminal restriction fragment length polymorphism. Soil Biology and Biochemistry. 39:590-599.