Influence of Micronutrients On Soybean Yield.

Ever-higher crop yields and a focus on whole plant nutrition is increasing grower interest in micronutrient applications to improve yields.  Numerous micronutrient products are available that differ in elemental composition, chelate, and application method.  However, the effects of these formulations on soybean (Gycine max [L.] Merr.) yield and grain quality are unclear.  A three-year experiment was initiated in 2011 at the Bradford Research Center (lat long) in central Missouri on a Mexico silt loam (fine, smectitic, mesic Vertic Epiaqualf).  MorSoy RT3930N soybean (MG 3.9) were sown in 38 cm rows and grown as part of a typical cropping system that includes rotation with corn (Zea mays L.) and pre- and post-emergent herbicide applications. Seven commercially available micronutrient formulations were applied according to labeled directions. Yield was determined on five 6.1 m long rows.  Protein and oil concentration was determined on a 100 g subsample by NIR spectroscopy.  Yield averaged 3.70 Mg ha^-1 across treatments and a trend of increasing yields with the application of most formulations was evident.  However, only one formulation, foliar-applied, non-chelated MnSO­₄, increased soybean yield relative to the control (P<0.05).  Protein and oil concentrations were not affected by micronutrient applications and averaged 396 and 210 g kg^-1, respectively across treatments.  Although results are preliminary, they suggest that micronutrients applications may improve soybean yields.  However, results from 2012 and 2013 will be necessary prior to making conclusions regarding these formulations.