Systematic Optimization of Yield-Enhancing Applications: Genetic Interactions.

Cultivar selection is the most important management decision that soybean producers can make each year.  New cultivars, possessing various trait/genetic backgrounds are continuously being introduced into the market.  In addition, the use of multiple inputs (e.g. seed treatments, biological compounds, foliar fungicides and insecticides, etc.) has increased.  However, it is not yet well understood how intensive management (i.e. multiple input use) interacts with cultivar selection.  Therefore, the objective of this study was to evaluate current, high-yielding cultivars under both high input and standard soybean management practices across the U.S. to better understand how management interacts with cultivar choice.  Research was conducted in nine states (AR, IA, IL, IN, KS, KY, MN, WI) as part of a three-year, multi-state project initiated in 2012.  At each location, six high-yielding cultivars were grown under 3 management levels : (1) untreated check (UTC), (2) “SOYA” (seed treatment fungicide, insecticide, and inoculant; Ratchet®; Task Force 2®; nitrogen fertilizer; BioForge®; Priaxor®; Endigo®), and (3) “SOYA” minus Priaxor®.  Individual site-year analysis found only 2 of 38 (5.3%) site-years had a significant cultivar by management interaction, which suggests cultivar selection most often does not dictate which inputs should be used.  Significant cultivar and management effects were observed in 26 of 38 (68.4%) and 24 of 38 (63.2%) site-years, respectively.  Across all locations, preliminary yield results from 2012-2013 indicated a management difference (P < 0.0001).  Managements 2 and 3 yielded 3.3 and 2.2 bushels acre^-1 better than management 1, respectively.  Yield component measurements (seeds m^-2, pods plant^-1, seeds pod^-1, and seed mass) indicated the yield response was due to increased seeds m^-2 and seed mass. Though yield increases where shown in management systems 2 and 3, grower return on investment would be negative given today’s commodity price.