Sulfur Distribution and Transformations in Everglades Agricultural Area Soil as Influenced by Sulfur Amendment

Nutrient export from the Everglades Agricultural Area (EAA) has been implicated in causing sulfur (S) enrichment of Everglades wetlands. However, quantification of the S budget and transformations in EAA soils is inadequate. The objective of this study was to quantify various S fractions and investigate how elemental S amendment affects S dynamics in EAA soils. Reduced S compounds were not detected in soil before elemental S application. Organic S was the major form of S, comprising 87% of total S, followed by extractable SO4-S (13%). Extractable SO4-S for soils receiving 448 kg S ha(-1) was 36%, 131%, 201%, and 270% higher than for unamended soils at 2, 6, 9, and 13 months, respectively. Elemental S was significantly higher in soils receiving 448 kg S ha(-1) (482 mg kg(-1)) than in soils receiving 224 (111 mg kg(-1)) and 112 kg S ha(-1) (55 mg kg(-1)) and unamended soil (0 mg kg(-1)) at 2 months after S application. Similar to extractable SO4-S, elemental S significantly decreased during the growing season. Sulfur application did not affect the sulfatase activity, however, mineralizable S increased concurrently with S application rate, and the effects continued throughout the growing season. This result was largely attributed to the oxidation of the applied elemental S. Our results suggest that large-scale S application in the EAA soils is likely to increase SO42- concentrations in soils, which poses a potential risk of SO42- export to sensitive Everglades wetlands.