Performance of Sulfur Diagnostic Methods for Corn
2011
Pagani, Agustín | Echeverría, Hernán E.
Sulfur availability indicators are necessary for rational use of S fertilizers. There are disagreements, however, about which S diagnostic method provides the best results for many crops. This work evaluates the performance of different S diagnostic methods for corn (Zea mays L.). Five field experiments with different rates of S and sufficiency of other nutrients were conducted in two contrasting areas in the Argentinean Pampas region. Measurements of some soil properties, grain yield, N and S concentration in total biomass, and chlorophyll meter readings (CMR) at upper and middle layers of the canopy were performed. Sulfur application significantly increased grain yield in four of the five experiments. Fertilization with S also increased total biomass, S concentration, and CMR depending on the experiment and crop stage, but rarely N concentration in total biomass. Soil indicators (especially sulfate-S availability) did not perform well as predictors of S response. Total S concentration and N/S ratio in biomass could be used to help characterize the S nutritional status at physiological maturity, since 89 and 72% of the samples were correctly characterized considering thresholds of 0.0095 g kg⁻¹ and 11:1, respectively. Leaf greenness intensity could have a high potential as a predicting/characterization methodology of corn S status since acceptable linear relationships were found between corn relative yield (RY) and a new sulfur sufficiency index (SSI), based on CMR (R² = 0.56 and 0.75 for the middle and the upper crop layer, respectively). Further research in areas with high levels of S deficiency will have to be done to validate the findings presented in this study.
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