Agronomic management of soybean with foliar manganese and apical meristem alterations

About half of soybean [Glycine max (L.) Merr.] yield is attributed to genetic improvements of 12.5 kg ha-1 per year (Specht and Williams, 1984) with the remaining half of soybean yield being dependent upon environment, agronomic management, and the interaction of genetics and management (Rowntree et al., 2013). Many farmers have overlooked the importance of incorporating management practices into their soybean production system, which indicates they may be missing half of the potential yield of soybeans. Therefore, our objective was to quantify the impact of different agronomic management practices on soybean productivity. One study was conducted in 2014 and 2015 to determine the value of the foliar application of two different foliar manganese products to relieve "yellow flashing" in glyphosate resistant soybeans sprayed with the herbicide glyphosate. Foliar manganese applied 24 hours prior to glyphosate applications led to the greatest increase in plant manganese concentration. Although applications of either manganese formula increased plant manganese concentration, they did not result in a consistent impact on total biomass, plant chlorophyll, or final yield; however, chlorophyll measurements as well as visual observation did not indicate "yellow flashing" in either year. A second experiment in 2015 evaluated alternative practices to break apical dominance in soybean in order to facilitate plant branching or create multiple new main stems to potentially increase yield. Practices to eliminate the plant apical meristem included applying the herbicide Cobra (2-ethoxy-1-methyl-2-oxoethyl-5-[2-chloro-4-(trifluoromethyl)-phenoxy]-2-nitrobenzoate) to cause a chemical burn, as well as decapitation back to the unifoliate or first trifoliate nodes. Plant population (80,000 vs 160,000 plants acre-1) was also a factor in this study as soybean plants tend to naturally branch more at lower populations. All apical meristem removal treatments resulted in a significant yield decrease, with greater penalties occurring at the lower plant population (80,000 plants per acre). Collectively, these findings emphasize the importance of providing the soybean plant a stress-free growing season to maximize yield