/AnMtgsAbsts2009.52971 Seasonal Dynamics of Phosphorus in Sulfur-Amended Organic Soils of South Florida.

Wednesday, November 4, 2009
Convention Center, Exhibit Hall BC, Second Floor

Rongzhong Ye, Univ. of Florida, Gainesville, FL, Alan Wright, Everglades Research & Education Center, Univ. of Florida, Belle Glade, FL, J. Mabry McCray, Agronomy, Univ. of Florida, Everglades Res. & Edu. Center, Belle Glade, FL and K. R. Reddy, Wetland Biogeochemistry Laboratory, Univ. of Florida, Gainesville, FL
Abstract:
The Everglades Agricultural Area (EAA) in south Florida was drained in the early 1900s for agricultural production. The dominant series is Histosols with organic matter content up to 80-90%.  Long-term tillage resulted in incorporation of CaCO3 into the soil profile from underlying bedrock, increasing the pH to approximately 7.0-7.5.  In some cases, elemental S is used to reduce soil pH for the purpose of increasing micronutrient and P availability, which may also increase P mobility and potential runoff from fields.  The objectives were to quantify the seasonal dynamics of P distribution in various fractions as affected by S amendment.  Elemental sulfur was introduced in granular form (90% S) at 0, 112, 224, and 448 kg S ha-1.  Phosphorus sequential fractionation was employed to determine sizes of different P fractions during the sugarcane growing season.  Pools of P fluctuated seasonally and their response to sulfur amendment varied.  Organic P was the major form in the soil while the Ca-bound P (Ca-P) dominated the inorganic fraction.  Labile P and Fe-Al bound P (Fe-Al-P) had the least contribution to total P and declined during the growing season, corresponding to P uptake patterns by sugarcane.  The size of Ca-P fraction was relatively stable but also subject to decrease during the growing season.  Humic-fulvic acid P and residual P fluctuated seasonally.  Total P stocks declined over time as a result of continuous reduction in inorganic fractions by sugarcane uptake.  Application of sulfur at rates up to 400 lb S acre-1 had limited effects on altering soil pH.  Yet, a small reduction in soil pH did promote P accumulation in both labile P and Fe-Al-P fractions within 3 months of application.  None of the Ca-P, humic-fulvic acid P, and residual P responded to any rate of S addition.