Soil Phosphorus Forms in Hydrologically Isolated Wetlands and Surrounding Pasture Uplands

Newly created and restored wetlands play an important role in sequestering excess nutrients at the landscape scale In evaluating the long-term efficacy of nutrient management strategies to increase wetland capacity for sequestering P, information is needed on the forms of P found across the upland-wetland transition To assess this, we studied soils (0-10 cm) from four wetlands within cow-calf pastures north of Lake Okeechobee, FL Wetlands contained significantly (P < 0.05) greater concentrations of organic matter (219 g C kg(-1)), total P (371 mg P kg(-1)). and metals (Al, Fe) relative to surrounding pasture When calculated on an aerial basis, wetland surface sods contained significantly greater amounts of total P (236 kg ha(-1)) compared with upland soils (114 kg ha(-1)), which was linked to the concomitant increase in organic matter with increasing hydroperiod The concentration of P forms. determined by extraction with anion exchange membranes, I mol L-1 HCl, and an alkaline extract (0 25 mol L-1 NaOH and 50 mmol L-1 ethylenediaminetetraacetic acid [EDTA]) showed significant differences between uplands and wetlands but did not alter as a proportion of total P Speciation of NaOH-EDTA extracts by solution P-31 nuclear magnetic resonance spectroscopy revealed that organic P was dominated by phosphomonoesters in boils wetland and pasture sods but that myo-inositol hexakisphosphate was not detected in any sample The tight coupling of total C and P in the sandy sods of the region suggests that the successful management of historically isolated wetlands for P sequestration depends on the long-terns accumulation and stabilization of sod organic matter