Sugarcane Response to Elemental Sulfur In High pH Florida Histosols.

With subsidence of organic soils in the Everglades Agricultural Area, these soils are becoming shallower, with generally increased pH as more Ca carbonate from the underlying limestone is incorporated into the root zone. Elemental S has been recommended as a banded application at 560 kg/ha at pH > 6.6, but this recommendation has not been considered cost-effective by researchers and growers. The objective of this study is to update University of Florida recommendations for elemental S application for sugarcane grown on organic soil. Four small-plot experiments were established to compare rates of 0, 90, 224, and 448 kg S/ha applied in the furrow at planting as 90% S or STM5 (80% S, 5% Mn) granular materials. In addition, two previous trials (small-plot and field strip experiments) of furrow applications of elemental S were included in the study. There was a range of sugarcane yield (t sucrose/ha) responses in the six trials, with strong responses at two locations and smaller responses at two other locations. The largest response determined was with application of 448 kg S/ha as STM5 resulting in a 28% increase in t sucrose/ha across two years with an initial pH of 7.5.  The strongest responses were determined with soil pH near 7.5 or greater. Leaf Mn was generally a good predictor of reduced sugarcane yield, with 5 of 6 crops with summer leaf Mn < 16 mg/kg in zero S treatments having relative sucrose yield < 80%. Leaf Mn concentration related strongly to Mehlich 3-extractable soil Mn and Ca. With one year remaining in the study the available data indicates that soil pH, extractable Ca, and extractable Mn may be useful in a new soil test for updated elemental S recommendations.