2010 Annual Report 1a.Objectives (from AD-416) Identify soil microbiological indicators and quantify benefits of soil microbiological processes associated with agricultural management practices. 1b.Approach (from AD-416) Evaluate soil samples collected from agricultural lands under differing management for their bacterial and fungal qualities. Correlate microbiological data with management practice. 3.Progress Report The objectives of this research project are to advance the development of quantitative measures for soil biological benefits within sustainable cropping practices such as diversified rotation and cover cropping. Progress in FY-10 was primarily related to staffing the postdoctoral research position funded by this agreement. The near term research objectives are focused on the influence of cover crops on the mycorrhizal colonization of the successive corn crop and estimates of P benefit to that crop by the mycorrhizal fungi. Soil samples were collected in November, 2009 from research plots with differing cover crop varieties at two different sites, the ARS-Brookings research farm and a producer’s field in White Lake, SD. The number of mycorrhizal propagules (spores, vegetative hyphae, infected roots) was measured in these soils by most-probable number technique using Bahai grass as a host. Generally, there were low numbers of mycorrhizal propagules observed in these soils which have had a long history of inorganic fertilizer application. In June, 2010, corn roots were collected from both sites to measure the percent mycorrhizal colonization of the corn roots as influenced by the preceding cover crops. These measurements are proceeding.