Does Total Nitrogen/Sulfur Ratio Predict Nitrogen or Sulfur Requirement for Corn?

Core Ideas Nitrogen and sulfur can interact within the plant and affect the concentration of each other in corn plant tissue. Nitrogen concentration in plant tissue has a greater impact on the N/S ratio than S which was found to not affect the N/S ratio in corn ear leaf tissue and grain. Individual sufficiency of N and S in plant tissue is a better predictor of corn yield response versus the ratio of N/S in the plant tissue. The accumulation of nitrate–N in the base of the corn stalk assessed at maturity is decreased when sulfur fertilizer is applied. Excess sulfate can accumulate in the base of the plant at maturity but the amount of sulfate–S cannot be used to predict the sufficiency of S. Nitrogen and S can interact within the corn (Zea mays L.) plant. The objectives of this study were to evaluate in corn (i) the effect of N and S on nutrient uptake and grain yield, (ii) use of tissue total N/S ratio to predict grain yield, and (iii) the impact of applied SO₄–S on basal stalk NO₃–N concentration. Treatments were applied as a factorial design. Factor 1 consisted of 0 or 28 kg S ha‐¹. Factor 2 consisted of 0, 56, 112, 168, 224, and 280 kg N ha‐¹. Fertilizer N increased the concentration of N and S in corn R1 leaf tissue, N concentration in grain, relative grain yield, grain removal of N and S, and NO₃–N in the basal stalk. Fertilizer S increased R1 leaf N and S concentration, decreased basal stalk NO₃–N, and increased corn grain yield when N was applied at a rate that maximized corn grain yield. The total N/S ratio in corn R1 leaf and harvested grain were affected by N application but not by S addition. Basal stalk N/S ratio was affected by both N and S. A critical N/S ratio could not be identified to predict corn grain yield response. While the data support a general effect of N and S on the uptake of each other, fertilization with N or S should be based on potential for increased grain yield from either nutrient. Based on results, optimal N rates for corn are not affected if S is also applied.