Sulfur Forms and Management in Everglades Agricultural Area Soils.

Nutrient export from the Everglades Agricultural Area (EAA) has been implicated in causing sulfur enrichment of Everglades wetlands.  However, quantification of the sulfur 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.  Reduced S compounds were not detected in soil prior to or after elemental S application.  Organic S was the major form of S, comprising of 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 concurrent 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 SO₄ concentrations in soils, which poses a potential risk of SO₄ export to sensitive Everglades wetlands.