Quantifying the Effects of Nutrient Management and Cover Crops on Soil Microbial Communities and Soybean Production.

Agricultural productivity relies upon microbial communities to cycle nutrients from soil to plant yet little information is available concerning how nutrient management and cover cropping practices influence microbial activity and crop production. Lack of consistent soybean (Glycine max L.) yield response to applied fertilizer has resulted in a need to further investigate management practices focused upon enhancing soil biological activity which in turn may feed the crop. A field study was initiated in 2013 to determine the effects of cover crops and soil fertility on soybean soil biological activity, microbial composition, and plant production. The study was arranged as a split-plot randomized complete block with four replications each 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 fertilizer treatments including a non-fertilized check, a biotic 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. Soil DNA extraction occurred pre-plant, at R1, and pre-harvest from within and between soybean rows and was used to taxonomically classify soil bacteria. Data collection also included soil respiration to assess temporal changes in microbial abundance, R1 tissue sampling and nutrient analysis, R3 nodulation evaluation, grain measurements at physiological maturity (i.e., pods per node), and grain yield. Preliminary results concerning main and sub-plot effects of cover crop and fertilizer treatments with regards to soil bacterial classification will be discussed in addition to effects on soybean production.