The majority of the discussions have centered on the need for more nitrogen, and needing nitrogen earlier in the season.

Likewise, a few have recognized the need for proper phosphorus and potassium nutrient management to maximize nitrogen efficiency and increase yields. The plant nutrients sulfur and zinc are very important in corn production but are rarely discussed. The prevailing view is that the soil has enough. This may not be true in all cases or these nutrients may not be available early enough.

Sulfur is important in plant metabolism and nitrogen uptake. Approximately 90% of the sulfur needed comes from decomposition of organic matter/residue. In addition, sulfur is added from the air and fertilizer sources. The amount of sulfur we receive from the air has decrease from 11 to 12 pounds per acre per year (lbs./A/year) to 3 to 4 lbs./A/year as a result of cleaning up smoke stack emissions. Phosphate fertilizers like 0-20-0 once contained sulfur with gypsum as an impurity. The process of making ammoniated phosphate fertilizers—like 11-52-0 and 18-46-0—removes the gypsum and thus, the sulfur. Finally, higher corn yields over the last three to four years have mined more sulfur from the soil. As an example, a 120-bushel corn crop removes 20 pounds of sulfur, while a 200-bushel corn crop removes 33 pounds.

Zinc serves as a plant regulator in corn. Zinc deficiencies rarely show up in a corn-soybean rotation as the soybean year allows the zinc to be recharged in the soil. Continuous corn systems will not allow for the recharge and may cause zinc deficiencies and yield loss. This is particularly important in soils with high to very high phosphorus levels where additional phosphorus is added.

SOURCE: Dr. Dan Froehlich, U.S. agronomy manager for Mosaic

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