Jarrod O. Miller, Extension Agronomist, jarrod@udel.edu and Cory Whaley, Sussex Co. Extension Ag Agent; whaley@udel.edu
This is the typical time of year for sulfur (S) deficiencies to show up in our corn fields, starting in the V3-V5 growth stages. Sulfur is negatively charged and leaches from the upper root zone easily. Besides fertilizers, our most likely source of S in the soil is organic matter with maybe 5 lbs/acre coming from the atmosphere. With our cooler spring weather, it is possible that organic matter breakdown and release has been slower, so you may see fields that appear pale yellow in color (Figure 1) or have interveinal striping (Figure 2). Nitrogen deficiency will start on the older leaves, while S will often be across the whole plant (Figure 2).
Figure 1. Pale yellow patterns typical of S deficiency.
Figure 2. Closer inspection may reveal stripes (interveinal chlorosis) in some.
Many nutrients can have interveinal chlorosis, including Mn and Zn, so a tissue test will be necessary to be sure of the issue. For corn at this stage, S values should be within a range of 0.15 to 0.40% in the leaf tissue, although the field below with visual symptoms had a S value of 0.16%. You may also use the N:S ratio, which should be between 10 to 15 to diagnose problems.
As mentioned by Dr. Amy Shober last week (https://sites.udel.edu/weeklycropupdate/?p=15022), sidedressing is a good time to correct S deficiencies, which can be accomplished with fertilizers such as ammonium sulfate or N-Sol.