Corn Response to ZINC Application in Argentinean Molisols.

Corn crop production in Argentina has significantly increased in the last years explained by better management practices such as nitrogen and phosphorus (P) fertilization and, occasionally, sulfur fertilization. In general, lack of zinc (Zn) fertilization, decreases in soil organic matter (OM) and Zn uptake have diminished soil available Zn. The objective of this study was to determine the effect of Zn fertilization on corn grain yield in Mollisols of Argentina. Forty six site-year trials were conducted during 2009-2013 growing seasons. One rate of Zn fertilization was compared with no Zn fertilization in small plots experiment design across the humid pampas region. In all sites OM, P Bray content, pH (water 1:2.5), and Zn (DTPA) were measured at 0-20 cm depth before planting. Depending on the site, Zn fertilization was applied at planting, or at V6 stage. Significant associations (P ≤ 0.05) were determined between OM or P Bray and soil Zn content (DTPA). However, coefficient of determination were low (r²= 0.10 to 0.11). On the other hand soil pH and soil Zn content (DTPA) were not associated (p ≥ 0.05). Significant site x Zn application interaction (P ≤ 0.01) was determined for grain yield as a consequence of different response to Zn fertilization across sites (range from -725 to 2430 kg ha^-1). In spite of this interaction grain yield was significantly affected (P ≤ 0.01) by site and Zn fertilization. Average grain yield varied from 4754 to 18404 kg ha^-1 across sites. Significant grain yield (p ≤ 0.10) average response of 1133 kg ha^-1to Zn application was found in 11 (24%) of 46 site-year. A Zn soil (DTPA) critical concentration of 1.0 ppm was determined to obtain 95% of relative grain yield. These results show that Zn would limit corn grain yield in some cultivated soils of Argentinean pampas region.