While the secondary macronutrient sulfur used to be adequately supplied through atmospheric deposition, times have changed, and we now receive almost zero sulfur via deposition.
Additionally, plant-available sulfur in the soil has been reduced by an estimated 34-86% over the last 20 years. This has led to sulfur deficiency symptoms in corn becoming more common.
Sulfur deficiency in corn is overall a lighter green plant color and chlorotic (yellow) stripes in between the veins (interveinal chlorosis) in the mid- to upper-crop canopy. These symptoms usually appear somewhere around V5 and will be persistent if sulfur deficiency is a problem for the plant.
Soil tests are not a reliable way to predict sulfur deficiency in Iowa soils. Generally, lower organic matter soils (less than 3.5%), sandy soils and those with eroded surfaces are most likely to need sulfur. But in more recent years, sulfur deficiency has appeared on higher organic matter and finely textured soils.
Fertilizing strips or blocks of fields with sulfur to test the crop response in-season is a useful way to evaluate whether a visual response occurs. A visual response in the early vegetative stages of corn is a good indicator of possible yield response and allows time for a side-dress application of sulfur.
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