Response to Zinc in Maize Crops in the Argentinian Pampas

Grain crops grown in the Pampas region of Argentina, especially maize, have shown Zn deficiencies. However, research on Zn responses in maize is scarce. The objectives of this research project were to: 1) quantify maize response to Zn in the Pampas region, 2) determine the optimum Zn rate for maize, and 3) validate local Zn analyses and critical levels. Eighteen field experiments were carried out in the 2009-10, 2010-11 and 2011-12 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 rates (0, 0.5, 1, 1.5, and 2 kg Zn/ha). Fertilizer sources used were MAP + urea (NP treatment), MES10^TM (12-40-0-10S; NPS treatment), and MESZ^TM (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.

Visual deficiency symptoms of Zn were observed at most locations. Significant grain yield responses to Zn 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. Argentina-29