Agronomic Maximization of Soybean Yield and Quality:Management Interactions.

Recently elevated commodity prices have caused a number of soybean growers to seek out management strategies that maximize yields and profits.  These management strategies include the use of various seed treatments, foliar fertilizers, growth promoters, stress reducers, defoliants and sub-threshold use of foliar insecticides and fungicides.  The purpose of this study was to evaluate these management strategies individually and as parts of high-yield soybean management systems.  Small plot studies were established at two or more sites in Michigan, Minnesota, Wisconsin, Iowa, Illinois, Indiana, Kansas, Kentucky, and Arkansas.  The studies were conducted in a randomized complete block arrangement and were maintained weed-free.  Individual treatments included a fungicide only seed treatment consisting of pyraclostrobin at 0.26 ml kg^-1 and metalaxyl at 0.52 ml kg^-1, a fungicide and insecticide seed treatment that included both fungicides as well as imidacloprid at 2.8 ml kg^-1, clothianidin and Bacillus firmus at 0.13 mg ai seed^-1 and a seed treatment consisting of both the insecticide and fungicide treatments and a combination of lipo-chitooligosaccharide (LCO) and Bradyrhizobium japonicum at 1.83ml kg^-1 followed by foliar LCO applied at 290 ml ha^-1 between V4 and V6.  Individual post-emergence treatments consisted of lactofen applied at 870 ml ha^-1 at V4, nitrogen applied at 168 kg ha^-1 at V4,  foliar fertilizer applied at 4.68 L ha^-1 at R1, pyraclostrobin applied at 440 ml ha^-1 at R3, lamda-cyhalothrin applied at 57 ml ha^-1 R3, N,N’-diformyl urea applied at 1.16 L ha^-1 at R3.  These treatments were combined to create combinations of management treatments.  When data were averaged across all locations, all treatments that contained foliar insecticide showed a significant yield advantage compared to the untreated control.  A yield advantage was also observed for N,N’-diformyl urea in certain environments.  The 2012 growing season was historically hot and dry at most locations in this study.  The study will be repeated in two more growing seasons to determine treatment effects under other environmental conditions.