Assessing corn response to sulfur fertilization in Kansas: Efficiency, optimum rate, and diagnostic tools

Abstract Corn ( Zea mays L .) response to sulfur (S) fertilizations remains difficult to assess due to the dynamic nature of S availability. This study evaluated corn response and diagnostic tools across 30 field sites in Kansas (Experiment 1; with and without S) and in complementary rate trials at two sites (Experiment 2; multiple S rates). Measurements included normalized difference vegetation index (NDVI), soil plant analysis development (SPAD), tissue S concentrations at various growth stages, grain S concentration, total S uptake, and yield. Sulfur fertilization increased tissue S concentration and uptake across stages, but yield responses were generally low. SPAD at R1 and tissue S concentrations outperformed NDVI and soil sulfate, although the diagnostic value was inconsistent. Grain yield and total S uptake showed a strong relationship, requiring 1.5 kg S uptake Mg −1 grain. In the rate study, yield followed a plateau response, and the agronomic optimum S rate was estimated at 21 kg ha −1 using model averaging of linear and quadratic plateau functions, while the 95% confidence interval (12–42 kg ha −1 ) was obtained using bootstrap aggregation. Efficiency metrics varied widely: agronomic and recovery efficiencies were low in nonresponsive sites but improved at lower rates in responsive environments, while internal efficiency averaged 619 kg grain kg −1 S uptake. Hierarchical Bayesian dilution models yielded a critical S concentration curve (S C = 2.05 × biomass −0.2 ) and a nitrogen‐to‐sulfur (N:S) ratio curve (N:S R = 15.59 × biomass −0.08 ), providing a physiological framework for in‐season diagnosis. Overall, moderate, well‐targeted S rates, combined with tissue diagnostics and dilution curves, can guide strategies to enhance S efficiency and management in corn.