Identifying Biotic and Abiotic Factors to Improve Soybean Production Via Soil Health.

Inconsistent soybean (Glycine max L.) yield in fields with similar growing conditions and management practices has generated the need to further examine factors influencing soybean productivity. A field study was initiated in 2013 to determine the effects of cover crops and soil fertility on soybean soil biological activity and yield. 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. 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 but oilseed radish significantly increased yield 67 kg ha^-1. Plant heights at V3 and R5, pods per node, rate of emergence, and yield were all significantly greater in soybean following oilseed radish. Preliminary results indicate that a winter-killing cover crop such as oilseed radish may also impact soil physical properties and indirectly benefit soybean yield.