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This article in SSSAJ

  1. Vol. 51 No. 3, p. 658-664
    Received: Aug 11, 1986

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Use of Soil-profile Sulfate Data for Predicting Crop Response to Sulfur1

  1. N. V. Hue and
  2. J. T. Cope Jr.2



Sulfur deficiencies in early growth stages do not always result in final yield reduction in many crops. This suggests a greater contribution of subsoil sulfate (SO4) and/or of S mineralization later in the season to the S requirements of plants. The subsoil SO4 contribution should be assessed in order to develop a method that can reliably predict crop response to S. A greenhouse experiment was conducted with various combinations of topsoil (0-20 cm layer) and subsoil (20-60 cm layer) materials from a Hartsells series (Typic Hapludult) where crop response to S had been observed, and a Benndale series (Typic Paleudult) where there was no response to S in field experiments. By determining soil SO4 depletion in each layer by crops of grain sorghum (Sorghum bicolor L. Moench.), it was extimated that plants derived approximately 0.55 of their S need from the surface 0 to 20 cm, and the remaining 0.45 from the subsoil. Subsequently, a weighted concentration of soil SO4 for the entire profile was calculated; and values of 13.8 mg S kg−1 for extractable SO4 and 0.25 mM for soil-solution SO4 were the minimum concentrations above which no crop response to S is expected. The use of weighted means of soil-profile SO4 data correctly predicted yield responses to S of soybeans (Glycine max L. Merr.), corn (Zea Mays L.), and sorghum in a field experiment, which were previously unexplained based on SO4 concentrations of the surface soil.

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