Microbial Community Composition and Diversity As Affected By Cover Crops and Soil Amendments.

Soil microbiota affect crop productivity via nutrient movement to plant roots, disease incidence, and other specialized relationships such as nodule formation in soybean (Glycine max L.). Few scientific data exist to explain the effects of cover crops or soil amendments on soil microbial community composition or soybean yield. A field study was initiated to determine the impact of cover crops and soil amendments on soil microbial community composition and plant production. The study was arranged as a split-plot randomized complete block with four replications containing 18 experimental units. Main plots consisted of cover crop preceding soybean and included oilseed radish (Raphanus sativus L.), hairy vetch (Vicia villosa Roth), or no cover crop. Sub-plots consisted of six soil amendments including a non-fertilized check, a biotic chicken manure-based fertilizer containing mycorrhizal inoculum, chicken manure, a biological soil inoculant applied to seed, a biological soil inoculant applied in-furrow, and inorganic N-P-K fertilizer application based on first-year nutrient mineralization of biotic and manure treatments. Ribosomal 16S DNA was extracted from soil samples taken pre-plant, R1 soybean growth stage, and pre-harvest. Additional data collection included monthly soil nitrogen monitoring, soil respiration to assess temporal changes in microbial biomass, R1 tissue sampling and nutrient analysis, plant height and chlorophyll measurements at V3 and R5, R3 nodulation evaluation, grain measurements at physiological maturity (i.e, pods per node), and grain yield. A significant 336 kg ha^-1 yield decrease was observed in 2013 when hairy vetch preceded soybean. In 2014 chicken manure application resulted in significantly greater yield than all other soil amendments besides inorganic N-P-K. Microbial DNA results for 2013 and 2014 will also be presented and discussed.