With planting season wrapped up, we’ve moved into scouting season. Hopefully you have been out walking your corn fields to evaluate your stands. At a distance, you may have noticed some fields that appear to be yellow. When inspected closely, you’ll notice that most of plants are yellow-striped new leaves with greener leaves beneath. This is a classic early season Sulfur deficiency symptom. Visual symptoms of Sulfur deficiency differ from Nitrogen deficiency, which is indicated by yellow leaves on the bottom of the plant.
Sulfur is present organically in soil. May’s wet weather limited the mineralization in the soil, leading to less available Sulfur. Soils that are naturally low in organic matter will obviously not have as much organic Sulfur, and will need fertilizer Sulfur. In fields with AMS applied this spring, Sulfur may have leached lower into the soil profile and out of the small root zone the plant currently has.
If you suspect Sulfur deficiency on your farm, tissue testing is a reliable and easy way to diagnose the issue. Choose two samples from the fields in question, testing samples of plants that show symptoms as well as green plants that do not show symptoms. Test results may indicate the need to apply additional Sulfur. Applying 50 lbs of dry AMS or 3 gal/ac of liquid Ammonium thiosulfate are the most commonly used methods to remedy Sulfur deficiency.
Over the past few days, fields have started to “green up” as the root system develops and as warmer soil begins to mineralize Sulfur. Scout your fields, take some tissue samples, and if necessary, apply additional Sulfur in coarse and low OM soils. Watch for greening plants as field conditions improve.