Agronomic Maximization Of Soybean Yield and Quality: Plant Population X Management Interactions.

Currently, many commercial products advertised to improve yield are available to soybean growers. Many of these products have been tested individually; however, their interaction with various management practices, including soybean plant population, has not been validated.  A cooperative multi-state field study was initiated during 2012 at two locations in Wisconsin, Michigan, Illinois, Indiana, Kentucky, Iowa, and Arkansas; three locations in Kansas; and four locations in Minnesota. The objective of this study was to determine how grain yield and seed quality respond to a more intensive management regime at varying plant populations. Two management regimes were evaluated (untreated and a high input system termed, SOYA complete) at six targeted seeding rates ranging from 123,500 to 494,000 plants ha^-1. The SOYA complete management regime consisted of multiple agricultural products currently being marketed to soybean growers (seed-applied fungicide, insecticide, biologicals, LCO promoters, and foliar-applied fertilizer, insecticide, fungicide) and were applied at labeled rates and timings. Stand counts were taken at V2 and R8 (full maturity) growth stages to confirm planting and harvest plant populations. Digital pictures were taken weekly to assess canopy closure and cumulative light interception. Overall, growing conditions were highly variable across locations and drought conditions during the 2012 growing season affected grain yield. Grain yield increased with increasing plant populations at all locations; however, maximum grain yield was dependent on growing region. The use of the SOYA complete management regime increased grain yield, but we did not find any interaction between SOYA complete and plant density. Field research will continue through the 2013 and 2014 growing seasons. The large number of site-years will allow for the development of comprehensive regional and national soybean production recommendations related to soybean inputs and seeding rates.