Use of Soil-profile Sulfate Data for Predicting Crop Response to Sulfur1
- N. V. Hue and
- J. T. Cope2
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.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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