Sulfur Fertilization of Winter Wheat Grown on Deep Sandy Soils

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AbstractSurface horizons of sandy Coastal Plain soils of the southeastern United States are low in available SO−24, and crops are often dependent upon adsorbed SO−24 in the B horizon. The objective of this study was to determine the response of winter wheat (Triticum aestivum L.) to sulfur (S) fertilization on three soils which varied in depth to the B horizon; a Wagram soil (Arenic Paleudults) > 50 cm to the B, and two Norfolk soils (Typic Paleudults) 31 and 48 cm to the B. Sulfur rates covered the range from 0 to 90 kg S ha−1. Sources used were CaSO4 · 2H2O, elemental S plus bentonite (Sol‐U‐Sul) and (NH4)2SO4. Measurements were made of S concentration and N/S ratio of plants, root distribution with depth at spike emergence and grain yield at harvest. Yield response to S fertilization was obtained on the Wagram soil and the Norfolk soil in which root growth was restricted by a tillage pan but not on the Norfolk soil with the B horizon at 31 cm. A rate of 20 kg S ha−1 as SO2−4 applied in late February was adequate for optimum response. Sol‐U‐Sul applied in February was not effective. Ammonium sulfate was equally effective as CaSO4. Plants responded to S fertilization where nonfertilized plants had S concentrations of 0.6 g kg−1 dry weight and N/S ratios of 21. Response of wheat to S fertilization depended upon the depth to the B horizon and root distribution in the soil profile. No response to S fertilization was obtained on a Norfolk soil in which there was appreciable root growth in the 30‐ to 45‐cm depth. That depth contained an accumulation of SO2−4. Where root growth was essentially restricted to the top 30 cm of a Norfolk soil in which SO2‐4 accumulation started at the 45‐cm depth there was a large response to S fertilization.