BY DR. RICK BATTY
Sulfur is sometimes the forgotten element in a grower’s fertility program. Its deficiency often goes unnoticed until symptoms such as leaf striping, reduced plant growth, and delay in maturity show up in your corn or beans. Even then a tissue analysis is required to identify the deficiency.
We never really needed to worry about adding sulfur to our fertility programs in the past, but the result of anti-pollution laws has reduced the amount of sulfur in rainfall by 8-10 lbs. per acre since 1985. In addition, yield levels for corn and beans have increased significantly and put an increased demand for adding sulfur to many fields of corn and bean production. Crop removal and leaching are the two main ways that sulfur leaves the soil. Wet springs can be especially damaging to sulfur levels (as you might guess) especially in the lighter soils. Crop removal alone will remove 25-30 lbs. of sulfur per acre of corn silage and 15-18 lbs. per acre for 200 bu. grain production. A 65 bu. soybean crop will consume 10-12 lbs. of sulfur.
Soil tests for sulfur availability have shown to be unreliable and inconsistent in determining sulfur availability and the need for additional sulfur application. Tissue sampling is considered to be far more reliable. The safest practice is to treat sulfur in the same way as one would do for nitrogen (N), phosphorus (P), and potassium (K), and make an application based on anticipated crop need for the year. Research across the Midwest has shown that applications of 25 lbs. of sulfur per acre broadcast for a corn crop and 15 lbs. for a bean crop would fulfill the needs in most fields.