Comparison of Impregnated Dry Fertilizer with S and Zn Blends for Corn and Soybeans.

Increased grain prices have renewed an interest in micronutrient management in Missouri’s high yielding corn and soybean systems. New formulation of monoammonium phosphate including sulfur and Zn allow for more uniform distribution. MicroEssential Sulfur-10 (MES10)(12-40-0-10S) and MicroEssential Sulfur and Zinc (MESZ)(12-40-0-10S-1Zn) with two forms of S (50% sulfate and 50% elemental S). The objectives of this research are to 1) evaluate P rates of MES10 and MESZ formulations to equivalent blends of MAP, Zn, and S, and 2) evaluate ZnSO₄ rates in a blend with MAP or DAP compared to MES10 and MESZ formulations on grain yields and uptake of micronutrients in a corn-soybean rotation. In objective 1, MESZ at 110 lbs P₂O₅/acre had high average corn (4 site-years).  Soil test Zn increased with all treatments that included Zn regardless of rate, and soil test SO₄-S increased with MES10 at 18 lbs S/acre, MES 10 at 28 lbs S/acre, MESZ at 18 or 28 lbs S/acre, and MAP + AMS at 28 lbs S/acre at Novelty in 2013.  Ear leaf P concentration was greatest with MAP + AMS at 110 lbs P₂O₅/acre and was similar to the high rates of MAP or MESZ. In objective 2, MESZ at 110 lbs P₂O₅/acre had the greatest yield average for corn (5 site-years). At sites with low soil test P and S, selective fertilizer treatments significantly increased soil test P and S following corn in 2013.  Soil test Zn increased with selective treatments at Novelty in 2013, but not at Albany with low or high initial soil test Zn.