Corn Grain Yield and Tissue Response to Foliar Zn 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 when seeded in cold, damp soils with relatively little organic matter.  Mississippi producers often find themselves in a situation where foliar application of Zn is needed to maximize corn yield after stand establishment.  Research was established between 2012 and 2014 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 Zn application was detrimental to corn grain yield.  At each siteyear trials were a randomized complete block design with treatments defined by 3 (Zn sources) x 3 (Zn application rates) factorial arrangement.  Response variables measured included visual crop injury at three, six, and nine days after application, tissue Zn concentration 2 wk after application, and corn grain yield.  Foliar Injury was observed with most products.  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 products, tissue Zn concentration increased with increasing application rate.  Data from four siteyears in the first two years 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.