Foliar Injury and Corn Grain Yield Response to Zinc Application.

Micronutrient fertilization is extremely important for balanced fertility, but is often overlooked when developing fertilization programs.  Monocot crops, such as corn (Zea mays L.), are very sensitive to Zn deficiency. Historically, the bulk of Zn research within Mississippi has investigated the influence of zinc fertilization on soils cropped to rice. Little research has evaluated the sole influence of zinc on corn growth and yield in Mississippi, or attempted to define soil test critical levels to predict yield response.  Research was established in 2012 and 2013 at multiple locations within the Mississippi Delta to evaluate the response of corn yield and tissue concentration to Zn application. A secondary objective was to determine if foliar injury from over the top zinc application was detrimental to corn grain yield.  Mean corn grain yields were increased at two of the three research sites in 2012. For the two responsive sites, grain yield was increased by 16 and 29 bu/acre for the DREC and the Boyle site, respectively.  Foliar applied citric acid chelated Zn produced significant foliar injury, with injury severity increasing at total Zn application rate increased.  In contrast, application of EDTA chelated Zn produced minimal to no foliar injury across the range of application rates.  The product x Zn rate interaction was non-significant for tissue Zn concentration collected 2 wk after application.  Averaged over Zn products tissue concentration increased with increasing application rate.  Preliminary data from two sites in the first year of testing suggest that grain yield is unaffected by foliar injury from application of citric acid chelated products.  However, trials were placed on corn that was seeded to soil that did not produce visual symptomology of zinc deficiency.  It is unclear if grain yield would be influenced by foliar injury symptoms if corn plants were Zn deficient.