Maize yield response to zinc sources and effectiveness of diagnostic indicators

Abstract: Maize yield is often limited by Zinc (Zn) deficiency. The objectives of this study were to i) Evaluate maize yield response to Zn applied at four different rates, ii). Evaluate the yield response and agronomic efficiency of maize to the application of a complex fertilizer, MicroEssentials® SZ™ (12-40-0-10S-1Zn), compared to different rates of mono-ammonium phosphate (MAP) + ammonium sulfate (AS) + zinc sulfate (ZnSO4), and iii). Evaluate the association between tissue Zn concentration and soil test Zn with the maize response to Zn fertilizer. Eleven experiments were carried out during the 2010, 2011 and 2012 growing seasons throughout eight states in the USA. Treatments consisted on four Zn rates of a physical blend of MAP + AS + ZnSO4 (0, 2.24, 4.48, 6.72, and 11.2 kg/ha Zn) and MicroEssentials SZ at a Zn rate of 2.24 kg/ha Zn. Nitrogen, phosphorus (P) and sulfur (S) rates were balanced across treatments (40 kg/ha P, 22 kg/ha S) and fertilizers were broadcast and incorporated immediately prior to planting. Treatment and location main effects were significant (P<0.001) on corn yields, whereas the interaction treatment x location was not (P=0.33). Maize responded positively to Zn fertilization; average yields across locations increased from 10,540 kg ha-1 without Zn to 11,530 kg ha-1 with 11.21 kg Zn ha-1 applied as a physical blend. The yield response and Zn agronomic efficiency of maize with the application of the complex fertilizer at a rate of 2.24 kg Zn ha-1 averaged 1004 kg ha-1 and 448 kg maize kg Zn-1, respectively, significantly higher (P