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(2009) Belmont, M.A., White, J.R. and Reddy, K.R. Phosphorus Sorption and Potential Phosphorus Storage in Sediments of Lake Istokpoga and the Upper Chain of Lakes, Florida, USA. Journal of Environmental Quality 38(3), 987-996.

Abstract
Phosphorus (P) can be an important nutrient in regulating primary productivity in lakes. The ability of lake sediments to retain P from external sources depends on the physiochemical characteristics of the sediment. To assess the P dynamics in Lake Istokpoga and the upper chain of lakes that drain into Lake Okeechobee, Florida, USA, sorption properties of batch sediment samples for Lakes Tohopekaliga, Cypress, Hatchineha, Kissimmee, and Istokpoga were characterized under aerobic and anaerobic conditions. Langmuir model parameters fit the experimental data well (in general, r(2) > 0.70). There were strong correlations between P sorption and total C, total P, Ca, Mg, Fe, and Al (r = 0.83-0.97). Equilibrium P concentration values ranged between 0.001 and 0.192 mg L-1 for aerobic conditions. A single-point isotherm (initial concentration, 5 mg L-1) was found for a wide range of sediment types, which allows estimation of the maximum potential sorption (S) as 1.7 times the sorption (S-max = 1.7 S-s). Results suggest that although these sediments have high P sorption capacities, the lake sediments may release P into the water column by desorption under aerobic conditions if water-column P concentrations are low enough (<0.036 mg L-1 for Lake Tohopekaliga and <0.003-0.027 mg L-1 for the other four lakes). Current watershed management strategies must balance efforts to reduce P inputs into the lakes from point and nonpoint sources against lowering the water-column P concentration to such a low level that the lake sediments become a source of P to downstream Lake Okeechobee.

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(2009) Cerna, B., Rejmankova, E., Snyder, J.M. and Santruckova, H. Heterotrophic nitrogen fixation in oligotrophic tropical marshes: changes after phosphorus addition. Hydrobiologia 627(1), 55-65.

Abstract
In order to determine the impact of nutrient enrichment on phosphorus (P) limited wetlands, we established experimental P additions in marshes throughout northern Belize. P significantly increased macrophyte primary production, which led to the rapid elimination of cyanobacterial mats. The replacement of cyanobacterial mats by macrophytes constrained autotrophic nitrogen (N) fixation, increased the quantity, and changed the quality of organic matter input to the sediments. We predicted that the activity of sediment heterotrophic N fixers will be impacted by these alterations in carbon input. We used the acetylene reduction technique to measure potential (glucose amended) nitrogenase activity (NA) in sediments from controls and treatment plots that have been P enriched for four years and dominated either by Eleocharis cellulosa, or Typha domingensis for two years. NA in P-enriched plots was 2-3 orders of magnitude higher than NA in controls. NA was positively correlated with the soil reactive P, both total organic and microbial carbon, live root biomass, and total phospholipid fatty acids (PLFA) as an indicator of active microbial biomass. It was negatively correlated with the concentration of ammonium-N. Path analysis revealed that the indirect effect of P on NA through the root biomass was more important than the direct effect of P. NA of the upper sediment layer was consistently higher in Eleocharis than in Typha dominated plots, despite the higher litter input by Typha. We feel that the higher levels of lignin and phenolics occurring in Typha litter, relative to Eleocharis, constrained NA in Typha plots.

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(2009) Chang, C.C.Y., McCormick, P.V., Newman, S. and Elliott, E.M. Isotopic indicators of environmental change in a subtropical wetland. Ecological Indicators 9(5), 825-836.

Abstract
The delta N-15 and delta C-13 signatures of major organic matter (OM) pools were measured across chemical and hydrologic gradients in a large (58,800 ha) subtropical wetland to evaluate whether stable isotopes were useful indicators of environmental change. Once a rainfall-driven wetland, the Loxahatchee National Wildlife Refuge in the Florida Everglades now receives agricultural and urban drainage that has increased phosphorus (P) and mineral loads around the wetland perimeter. Additionally, water impoundment at the southern end has produced a latitudinal hydrologic gradient, with extended hydroperiods in the south and overdrained conditions in the north. Detritus (-4.8 parts per thousand to 8.6 parts per thousand), floc (-1.4 parts per thousand to 3.6 parts per thousand), and metaphyton (-6.6 parts per thousand to +7.4 parts per thousand) delta N-15 declined southward with changes in hydrology as indicated by water depth. This pattern was attributed to higher mineralization rates under shorter hydroperiods. These signatures were also strongly correlated with increased nutrient and mineral loading. Rooted macrophyte delta N-15, by contrast, appeared more responsive to soil nutrient pools. Cattail (-8.9 parts per thousand to +7.7 parts per thousand) was restricted to the wetland perimeter and had the widest delta N-15 range, which was positively correlated with soil P. Sawgrass (-5.3 parts per thousand to +7.7 parts per thousand) occurred across most of the wetland, but its ON was not strongly correlated to any gradient. Patterns for delta C-13 were more strongly related to chemical gradients caused by canal intrusion than to latitude or hydrology. Again, metaphyton and detrital signatures were more sensitive to water chemistry changes than macrophytes. This pattern is consistent with their locations at the soil-water (detritus-floc), and air-water (metaphyton) interface. Metaphyton delta C-13 (-36.1 parts per thousand to -21.5 parts per thousand) which had the broadest range, was affected by DIC source and pool size. In contrast, cattail delta C-13 (-28.7 parts per thousand to -26.4 parts per thousand) was more closely related to soil P and sawgrass delta C-13 (-30.1 parts per thousand to -24.5 parts per thousand) was not related to any environmental gradient except latitude. There was no correlation between the two isotopes for any OM pool except cattail. These results indicate that isotopic signatures of microbial (metaphyton and detrital) pools are more responsive to changes in wetland hydrology and water chemistry while those of rooted macrophytes respond only to the extent that soil chemistry is altered. Rooted macrophytes also differ in the sensitivity of their isotopic signatures to environmental change. The selection of OM pools for isotopic analysis will, therefore, affect the sensitivity of the analysis and the resulting patterns. Furthermore, delta N-15 may be more robust and interpretable than delta C-13 as an indicator of ecosystem change in wetlands exposed to multiple or complex anthropogenic gradients.

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(2009) Conley, D.J., Paerl, HW, Howarth, RW, Boesch, DF, Seitzinger, SP, Havens, KE, Lancelot, C and Likens, GE. 2009.  Controling eutrophication: Nitrogen and Phosphorus. Science 323, 1014-15.

Abstract
Improvements in the water quality of many freshwater and most coastal marine ecosystems requires reductions in both nitrogen and phosphorus inputs.

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(2009) Escutia-Lara, Y., Gomez-Romero, M. and Lindig-Cisneros, R. Nitrogen and phosphorus effect on Typha domingensis Presl. rhizome growth in a matrix of Schoenoplectus americanus (Pers.) Volkart ex Schinz and Keller. Aquatic Botany 90(1), 74-77.

Abstract
In an outdoor mesocosm experiment of 80 weeks, the effect of nitrogen and phosphorus addition was tested on growth of Typha domingensis Presl. rhizomes in a matrix of Schoenoplectus americanus (Pets.) Volkart ex Schinz and Keller, under loading rates of 0.23 gm(-2) d(-1) of nitrogen, 0.17 gm(-2) d(-1) of P, both nutrient together and control conditions, to assess the potential expansion of T. domingensis in response to nutrient inputs. T. domingensis responded to nitrogen addition but not to phosphorus addition. When nitrogen was added, the number of rhizomes and their weight increased. Mesocosms with nitrogen had an average of 8 rhizomes, control mesocosms 5, the differences being significant (P < 0.05). Fresh rhizome biomass per mesocosm (0.58 m(2)) differed among treatments (P < 0.05): with nitrogen addition it was 110 (+/- 31) g, with phosphorus addition 71 (+/- 39) g, nitrogen and phosphorus 137 (+/- 57) g, control mesocosms 67 (+/- 30) g. The number and weight of rhizomes were highly correlated (Pearson's correlation = 0.84). Because T. domingensis responds to nitrogen additions by increasing the number and biomass of its rhizomes, it might be able to out-compete S. americanus when nitrogen concentrations increase. (c) 2008 Elsevier B.V. All rights reserved.

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(2009) Herbert, D.A. and Fourqurean, J.W. Phosphorus Availability and Salinity Control Productivity and Demography of the Seagrass Thalassia testudinum in Florida Bay. Estuaries and Coasts 32(1), 188-201.

Abstract
Biomass, net primary productivity (NPP), foliar elemental content, and demography of Thalassia testudinum were monitored in populations from five sites across Florida Bay beginning in January 2001. Sites were selected to take advantage of the spatial variability in phosphorus (P) availability and salinity climates across the bay. Aboveground biomass and NPP of T. testudinum were determined five to six times annually. Short-shoot demography, belowground biomass, and belowground NPP were assessed from a single destructive harvest at each site and short-shoot cohorts were estimated from leaf scar counts multiplied by site-specific leaf production rates. Biomass, relative growth rate (RGR), and overall NPP were positively correlated with P availability. Additionally, a positive correlation between P availability and the ratio of photosynthetic to non-photosynthetic biomass suggests that T. testudinum increases allocation to aboveground biomass as P availability increases. Population turnover increased with P availability, evident in positive correlations of recruitment and mortality rates with P availability. Departures from seasonally modeled estimates of RGR were found to be influenced by salinity, which depressed RGR when below 20 psu or above 40 psu. Freshwater management in the headwaters of Florida Bay will alter salinity and nutrient climates. It is becoming clear that such changes will affect T. testudinum, with likely feedbacks on ecosystem structure, function, and habitat quality.

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(2009) Inglett, P.W., D'Angelo, E.M., Reddy, K.R., McCormick, P.V. and Hagerthey, S.E. Periphyton nitrogenase activity as an indicator of wetland eutrophication: spatial patterns and response to phosphorus dosing in a northern Everglades ecosystem. Wetlands Ecology and Management 17(2), 131-144.

Abstract
The use of periphyton nitrogenase activity (biological N-2 fixation) as an indicator of wetland P impact was assessed using patterns of nutrient content (C, N, P, Ca, Mg, K, Fe, and Mn) and acetylene reduction (AR) in floating cyanobacterial periphyton mat (metaphyton) communities of a P-enriched portion of the Florida Everglades, USA (Water Conservation Area-2A, WCA-2A). Spatial patterns of nutrients indicate the enrichment of floating mat periphyton N, P, Fe, and K, and the reduction of Mn and TN:TP in enriched marsh areas. In highly enriched areas, floating mat periphyton AR was approximately threefold greater than that in less enriched, interior marsh zones. Multiple regression models indicated AR dependence on P in eutrophicWCA-2A areas while the AR of more interior marsh periphyton mats was more closely related to tissue levels of Ca and Fe. Nitrogenase activity of floating mat periphyton from P-loaded mesocosms revealed a significant enhancement of N-2 fixation in samples receiving approximately 2-3 mg P m(-2) of cumulative P dosing or with biomass TP content of 100-300 mg kg(-1). At P contents above the optimum, mat periphyton AR was suppressed possibly as a result of changes in species composition or increased levels of NH4+. After 3 years of dosing, consistently high AR occurred only at low rates of P enrichment (0.4-0.8 g P m(-2) yr(-1)), and the patterns appeared to be seasonal. These findings agree with the hypothesis that P availability is a key determinant of nitrogenase activity in aquatic systems, and thus, may support the use of periphyton nitrogenase to indicate P impacts in P-limited systems. These results also demonstrate the potential existence of a P threshhold for biogeochemical alteration of periphyton mat function in the Everglades, and that cumulative loading of limiting nutrients (i.e., P), rather than instantaneous concentrations, should be considered when evaluating nutrient criteria.

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(2009) Lai, D.Y. and Lam, K.C. Phosphorus sorption by sediments in a subtropical constructed wetland receiving stormwater runoff. Ecological Engineering 35(5), 735-743.

Abstract
This study investigated the potential of using a mixture of fishpond bund material, completely decomposed granite and river sand as substrate in a constructed wetland for phosphorus removal. Core samples were collected from the newly constructed Hong Kong Wetland Park (HKWP) receiving influent stormwater from a nearby new town, and batch incubation experiments were conducted to determine the P sorption characteristics of sediments. The HKWP sediments adsorbed the majority of available P in the initial 20 min of incubation, with a first-order rate constant of 1.01-2.11 h(-1). Sediments in the reedbeds and freshwater marshes possessed a great capacity for P adsorption with the high Langmuir sorption maxima (478-858 mg kg(-1)) and Freundlich adsorption constants (417-672 L kg(-1)) obtained, attributable to the high amorphous iron and aluminium concentrations compared to other constructed wetlands. Moreover, sediment equilibrium P concentrations were generally low (4.6-23.6 mu g L-1), facilitating a net P adsorption by sediments under moderate P loadings. Yet, the amount of P adsorbed by the HKWP sediments was limited by the low ambient porewater P concentrations and there was even a risk of P desorption when sediments in the freshwater marshes were resuspended into the water column. While substrates in the HKWP demonstrated a great potential for P adsorption, consideration should also be given to P loadings in influent water to fully utilize the P sorption capacity of sediments and enhance the P removal efficiency of constructed wetlands.

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(2009) Malecki-Brown, L.M. and White, J.R. Effect of Aluminum-Containing Amendments on Phosphorus Sequestration of Wastewater Treatment Wetland Soil. Soil Science Society of America Journal 73(3), 852-861.

Abstract
Little research has been conducted on methods to restore the P removal capacity of older constructed wetlands, as P treatment capacity can decrease with time. We investigated the capacity of alum and three Al-containing alternatives (alum residual, polyaluminum chloride [PAC], and partially neutralized aluminum sulfate [PNAS]), at three rates (9, 18, and 36 g Al m(-2)) to reduce P concentrations. Water column pH of the alum treatment was significantly less than all other treatments, averaging 3.65 +/- 1.12, while PAC (4.85 +/- 0.96) and PNAS (4.21 +/- 0.93) treatments had pH values significantly less than the alum residual and controls. Soluble reactive P decreased in the water column of all the treatments (-60.41 to -2.11 mg m(-2) d(-1)). At all dosage rates, alum and PNAS were most effective at binding P, followed by PAC, while the alum residual was least effective. Significantly less P removal occurred in the 9 g Al m(-2) alum, PNAS, and PAC treatments than the higher Al dosages. Dosage was inversely related to microbial biomass and activity in the surface soil, suggesting short-term negative effects of chemical additions. Results suggest that a low-dosage Al amendment application to wetland soil can, in the short term, prevent release of P from organic soil into the water column as well as remove P from the water column. Longterm studies are needed, however, to verify P removal efficacy with time and the effects of continued applications on nutrient availability.

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(2009) McCormick, P., Newman, S. and Vilchek, L. Landscape responses to wetland eutrophication: loss of slough habitat in the Florida Everglades, USA. Hydrobiologia 621(105-114.

Abstract
Much of the historical Everglades has been either lost or degraded as a result of human activities. Among the aquatic habitats that comprise the Everglades landscape mosaic, open-water sloughs support critical ecological functions and appear especially sensitive to both hydrologic and water-quality perturbations. We used a combination of remote sensing and on-the-ground sampling to document spatial changes in the extent and vegetative composition of sloughs along a phosphorus (P) gradient in the northern Everglades. Increasing levels of water and soil P were associated with a decline in slough coverage, loss of the abundant native periphyton community, and a shift in dominant macrophyte species. The characteristic slough macrophyte species Eleocharis cellulosa and Nymphaea odorata exhibited different sensitivities to P enrichment, but both species declined with enrichment as slough habitats were invaded by Typha domingensis, a species that is known to expand aggressively in response to enrichment. A limited amount of open-water habitat occurred in highly enriched areas, but these habitats were maintained largely as a result of airboat disturbance and did not contain characteristic slough vegetation. Many changes in slough coverage and composition occurred in areas where water and soil P concentrations were only marginally higher than background levels. Our findings support the need for Everglades hydrologic restoration efforts to adhere to strict water-quality standards for P to avoid further degradation of this key landscape feature.

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(2009) Mukherjee, A., Nair, V.D., Clark, M.W. and Reddy, K.R. Development of Indices to Predict Phosphorus Release from Wetland Soils. Journal of Environmental Quality 38(3), 878-886.

Abstract
The U.S. Environmental Protection Agency created the Clean Water Action Plan to develop nutrient criteria for four water body types: lakes and reservoirs, rivers and streams, estuaries, and wetlands. Significant progress has been made in open water systems. However, only areas in and around the Florida Everglades have had numeric nutrient criteria set, due to the complexity, heterogeneity and limited information available for wetlands. Our objective was to evaluate various soil tests to predict significant P release potential of soil in wetlands. A total of 630 surface soil samples (0-10 cm) were collected for this study from four southeastern states: Florida, Alabama, Georgia, and South Carolina. Soil samples were collected from the center of wetlands, the edge of the wetlands, and from adjacent uplands. The phosphorus saturation ratios (PSR), calculated using P, Fe, and Al molar concentrations from Mehlich 1 (M1-PSR), Mehlich 3 (M3-PSR), and oxalate (Ox-PSR) extractions and the amount of P extracted by different excractants were used to predict P loss potential from a soil. Total phosphorus (TP) concentration in wetland Soils, estimated as the 75th percentile of the distribution of least impacted wetland soils as an example, was approximately 550 mg kg(-1). Based on this reference background condition, procedures for obtaining threshold values for P release to the surrounding water bodies were developed and threshold values calculated: 1-P 24 mg kg, M3-P = 44 mg kg(-1), Ox-PSR = 0.079, M1-PSR 0.101, and M3-PSR = 0.067

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(2009) Qian, Y., Miao, S.L., Gu, B. and Li, Y.C. Effects of Burn Temperature on Ash Nutrient Forms and Availability from Cattail (Typha domingensis) and Sawgrass (Cladium jamaicense) in the Florida Everglades. Journal of Environmental Quality 38(2), 451-464.

Abstract
Plant ash derived from fire plays an important role in nutrient balance and cycling in ecosystems. Factors that determine the composition and availability of ash nutrients include fire intensity (burn temperature and duration), plant species, habitat nutrient enrichments and leaf type (live or dead leaf). We used laboratory simulation methods to evaluate temperature effects on nutrient composition and metals in the residual ash of sawgrass (Cladium jamaicense) and cattail (Typha domingensis), particularly on post-fire phosphorus (P) availability in plant ash. Live and dead leaf samples were collected from Water Conservation Area 2A in the northern Everglades along a soil P gradient, where prescribed fire may be used to accelerate recovery of this unique ecosystem. Significant decreases in total carbon and total nitrogen were detected with increasing fire temperature. Organic matter combustion was nearly complete at temperatures >= 450 degrees C. HCl-extractable P (average, 50% of total P in the ash) and NH4Cl-extractable P (average, 33% of total P in the ash) were the predominant P fractions for laboratory-burned ash. Although a low-intensity fire could induce ail elevation of P availability, an intense fire generally resulted in decreased water-soluble P. Significant differences in nutrient compositions were observed between species, habitat nutrient status, and leaf types. More labile inorganic P remained in sawgrass ash than in cattail ash; hence, sawgrass ash has a greater potential to release available P than cattail. Fire intensity affected plant ash nutrient composition, particularly P availability, and the effects varied with plant species and leaf type. Therefore, it is important to consider fire intensity and vegetation community when using a prescribed fire for ecosystem management.

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(2009) Saha, A.K., Sternberg, L. and Miralles-Wilhelm, F. Linking water sources with foliar nutrient status in upland plant communities in the Everglades National Park, USA. Ecohydrology 2(1), 42-54.

Abstract
Plant communities within an ecosystem can vary in water source usage and nutrient availabilities, thus permitting community coexistence and diversity. We investigated the differences in water source utilization in two ecologically important upland plant communities: tropical hardwood hammocks and pine rocklands in the predominantly flooded Everglades ecosystem. We then linked these differences with their foliar nutrient levels and photosynthetic performance as measured by delta C-13 abundance. Based on a comparison of delta O-18 of plant stem waters with those of potential water sources (nutrient-poor groundwater and nutrient-rich water in organic litter referred to as soilwater), we observed that during the wet season hammock plants relied on soilwater while in the dry season they relied on groundwater. A similar seasonal shift was observed in pineland plants, however, groundwater constituted the major part of water uptake throughout the year except for late wet season. Consistent with the nutrient concentration of different water sources used in the two communities, hammocks had a greater annual mean foliar nitrogen and phosphorus concentration at the community level over pinelands as well as a higher leaf area index. High foliar N concentration in hammock plants was associated with eventual stomatal limitation of photosynthesis. Hammock species being intolerant of flooded soils are restricted to water uptake in the shallow unsaturated soil layer in the wet season, yet access the lowered groundwater table in the dry season. This dependence on a relatively narrow annual range of water table levels should be considered in South Florida water management and Everglades restoration.

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(2009a) Wright, A.L. Phosphorus sequestration in soil aggregates after long-term tillage and cropping. Soil & Tillage Research 103(2), 406-411.

Abstract
Cultivated soils in the Everglades are being converted to their historic use as pastures or seasonally flooded prairies as parts of restoration efforts, but long-term cultivation may have altered soil P distribution and availability which may pose eutrophication hazards upon change in land use. The objectives of this study were to determine the distribution of P in soil chemical and physical fractions for contrasting long-term land management practices. The distribution of P in labile, Fe-Al bound, Ca bound, humic-fulvic acid, and residual pools in five aggregate-size fractions were measured for fields under sugarcane (Saccharum sp.) cropping for 50 years and perennial pasture for 100 years. Both land uses were characterized by a high degree of macroaggregation, as aggregates >0.25 mm contained 76 and 83% of the total soil under cultivation and pasture, respectively. Soils under sugarcane sequestered a total of 77 kg ha(-1) more P than pasture at 0-15 cm. The distribution of P in chemical fractions significantly varied between land uses as cultivation increased P sequestration in Ca-bound fractions more for sugarcane (244 kg P ha(-1)) than pasture (65 kg P ha(-1)). Pasture sequestered more P in organic pools, as storage in humic-fulvic acid and residual fractions were 26 and 25%, respectively. higher than sugarcane. Labile P was 100% higher for pasture than sugarcane, but Fe-Al bound P storage did not differ between land uses. Aggregation increased P sequestration in humic-fulvic acid and residual fractions, and P storage in organic pools increased with increasing aggregate size. In contrast, cultivation decreased aggregation and increased P accumulation in inorganic fractions. Long-term cultivation altered the distribution of soil P from organic to inorganic pools. The P stored in inorganic pools is stable under current land use, but may be unstable and pose eutrophication hazards upon onset of future land use change to the seasonally flooded prairie ecosystem.

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(2009b) Wright, A.L. Soil phosphorus stocks and distribution in chemical fractions for long-term sugarcane, pasture, turfgrass, and forest systems in Florida. Nutrient Cycling in Agroecosystems 83(3), 223-231.

Abstract
Phosphorus distribution and stability in soils of the Everglades Agricultural Area (EAA) of south Florida is important because of changing land uses. We investigated the effects of land use on P distribution in the soil profile and between chemical fractions for a histosol of the Florida Everglades. Labile, Fe-Al bound, Ca-bound, humic-fulvic acid, and residual P pools in 0-15, 15-30, and 30-45 cm depths were determined for drained soils planted to sugarcane (Saccharum sp.) for 50 yr, pasture for 100 yr, turfgrass for 60 yr, and forest for 20 yr. The P concentrations of all chemical fractions decreased with depth in the profile, indicating accumulation in surface soil resulting from oxidation and fertilization. Trends in P distribution between chemical fractions were similar between land uses. Labile P comprised less than 1% of total P. Fe-Al bound P averaged 2.9% of the total P for turfgrass and forest, but 11.4 and 9.6% for sugarcane and pasture. Increasing soil disturbance and long-term fertilization increased P allocation to inorganic fractions, as Ca-bound P contained 49% of total P for sugarcane but 28% for other land uses. Total P stocks in the soil profile (0-45 cm) averaged 1,323, 2,005, 2,294, and 2,317 kg P ha(-1) for pasture, sugarcane, turfgrass, and forest, respectively. Under current land uses P in organic fractions represents an unstable pool since the soil is prone to oxidation under drained conditions. In contrast, P sequestered in inorganic fractions is more stable under current land uses, thus sugarcane cultivation and incorporation of bedrock CaCO3 into surface soil by tillage will enhance long-term P sequestration.

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(2008) Castillo, M.S. and Wright, A.L. Soil phosphorus pools for Histosols under sugarcane and pasture in the Everglades, USA. Geoderma 145(1-2), 130-135.

 

 

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