To raise high-yielding crops, sulfur is a key element, yet many soils lack the amount needed to reach maximum potential. Reduced atmospheric depositions, increased yield and crop removal, and high amounts of crop residue all are reasons sulfur deficiencies are becoming more frequent.

Sulfur can be one of the most limiting factors in high-yielding corn and soybean production systems. Respectively, 10 pounds of sulfur are removed for a 200-bushel-per-acre corn crop and a 60-bushel-per-acre soybean crop.

Increases in no-till have promoted immobilization and stratification of nutrients. During decomposition, nutrients such as nitrogen and sulfur become temporarily unavailable as residue is broken down.

Sulfur deficiency can affect both quality and yield of grain. It plays an important part in forming proteins, developing enzymes and vitamins, promoting nodule formation, producing seeds, and forming chlorophyll. Adequate sulfur helps seedlings survive in cool, moist soil conditions and helps promote rapid root development during early stages of growth. 

Sulfur deficiencies commonly appear as a pale green or yellowish color on lower leaves first and gradually move across the entire plant. Yellow striping symptoms in corn can be confused with magnesium deficiency.

If ever in doubt, send in leaf samples for a diagnosis. Usually, potential yields will already be affected by the time visual symptoms are noticed, making it more important to be proactive versus reactive with soil fertility plans.  

Like nitrate, sulfate sulfur leaches in the soil, but not as easily. Sulfur is needed in significant quantities to push yields, especially in sandy soils. Humus is a component of organic matter and is key for holding sulfur in the soil. The higher the humus content, the less likely the need for sulfur. The goal with sulfur fertility is to help ensure it is available to corn post tassel. 

Since sulfur is leachable in the soil, fertilizer applications should be made as close to crop need as possible. Many sulfur-containing fertilizers are available, convenient and cost-effective to apply.

In season, the most reliable method to determine adequate sulfur levels is to sample the ear leaf. While sampling this late may not help the current crop, it can provide information needed for the next crop. In general, it is recommended that for loam and loam clay soil types, 15 pounds per acre of actual sulfur be applied, and for sandy soil types, 25 pounds per acre of actual sulfur be applied. 

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