Response to Zinc in Maize Crops in the Argentinian Pampas

Grain crops grown in the Pampas region of Argentina, especially maize, often show zinc (Zn) deficiencies. However, research on maize response to Zn fertilization is scarce. The objectives of this research project were to: 1) quantify maize responses to Zn fertilization in the Pampas region, 2) determine the optimum Zn application rate for maize, and 3) validate local Zn analyses and critical levels. Eighteen field experiments were carried out between 2009 and 2012 in the maize-growing seasons at different locations in the Pampas region including: Alejo Ledesma, Chaján, Adelia María, Guatimozin, and Rio Cuarto sites in Cordoba; San Justo, M. Teresa, Rafaela, Wheelwright and Oliveros sites in Santa Fe; and 9 de Julio, Balcarce, Lincoln, Pergamino, and Gral. Villegas sites in Buenos Aires. Treatments included NP, NPS and NPS with different Zn application rates (0, 0.5, 1, 1.5, and 2 kg Zn/ha ). Fertilizer sources used were MAP + urea (NP treatment), MicroEssentials S10TM (12-40-0-10S; NPS treatment), and MicroEssentials ZnTM (12-40-0-10S-1Zn; NPS plus Zn treatments). Nitrogen, P and S rates used were 80 kg N, 35 kg P and 20 kg S. All fertilizer applications were made at planting time.

Visual deficiency symptoms of Zn were observed at most locations. Significant positive grain yield responses to Zn additions were observed at 12 of the 18 sites. Average maize grain yields for the 18 experiments were 10.3, 10.5, 10.6, 10.8, and 10.7 t/ha for Zn application at 0, 0.5, 1, 1.5, and 2 kg Zn/ha, respectively. Optimum Zn rates varied between 1.0 and 2 kg Zn/ha, depending on the location. The average Zn response, when Zn was applied at 1.5 kg Zn/ha, was 4.7% (+487 kg/ha). No negative responses to Zn application were observed at any of the studied locations.

Four additional experiments were carried out in the 2012/13 growing season to evaluate Zn response in late-season maize crops. Experiments were located at southern Cordoba and western and northern Buenos Aires. Response to Zn application was significant at Pergamino site, with a yield increase of 9% (+720 kg/ha) when Zn was applied at 1.5 kg Zn/ha. Four field experiments will be established in the 2013/14 growing season to complete the evaluation of Zn response in late season maize.