Lecture 19 Phosphorous

Lecture 19 Phosphorous - Phosphorous Phosphorous Organic...

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Unformatted text preview: Phosphorous Phosphorous Organic Phosphorous Organic Components of soil organic matter and plant tissue Phosphate sugars Nucleic Acids (DNA/RNA) ATP Phospholipids ATP Importance Importance Essential Macronutrient Limiting Resource Present in Fertilizers, animal wastes, wastewater Availability can be very limited Fertility Fertility -Total soil phosphorous is low -Most of the total is unavailable to plants -Much of soil P forms insoluble solids (limiting to availability) 10 -15% of applied fertilizer phosphorous used by plants 85 – 90% is bound to soil particles or forms insoluble solids =>excess application =>saturation of soil capacity => mobility in the environment Unimpacted P-impacted Soil Phosphorous Soil Inorganic PO4-3 (Orthophosphate) H3PO4 H2PO4- HPO4-2 The form of available phosphorus is pH-dependent Plant Availablity Plant H2PO 4 pH 3-6 Most Available pH 6-8 HPO4-2 pH 8-11 Optimum pH = 6.5 for mineral soils Acidic Soils Acid Soils (Low pH) Acid Aluminum and Iron availability increased at low pH FeOOH Al(OH)3 Solubility increased Al3+ Fe3+ example Al(OH)3 + 3H+ = Al3+ + 3H2O Aluminum Precipitation at Low pH Aluminum Form of available P at low pH: H2PO4- (pH 3-6) H PO combines with free Al and Fe 2 (Insoluble)3+ 3+ 4- Al3+ + H2PO4- + 2H20 = Al(OH)2H2PO4 + 2H+ Al(PO4) • H2O simplified Al 3+ + PO = Al(PO4) 4-3 Variscite Basic Soils (High pH) Calcium Binding in Basic Soils Calcium CaCO3 (higher calcium availability) H2(PO4)- is the available form of P CaCO3 + 2H2(PO4)- = Ca [H2(PO4)]2 + CO32CaHPO 4 Ca (PO ) OH (Apatite mineral) 5 43 Availability and pH Availability Formation of insoluble solids Low pH Aluminum and Iron phosphates High pH Calcium Phosphates Reaction with Soil Minerals Reaction Fixation on Iron and Aluminum Fixation A dominant interaction between Phosphorus and soils is strong interaction with Iron and Aluminum Oxides OH Al OH Fe OH Al OH Fe OH OH Fixation: Aluminum/Iron oxides Fixation: OH OH Fe Fe OH + H2(PO4)- H2(PO4)FE Fe OH OH + OH- OH O Fe OH + Fe O- P- OH OH OH OH O O- P- Fe Fe OH OH OH Coatings on Sands and Silicate Clays Coatings OH Fe H2(PO4)Fe OH Fe coating Organic Matter Organic matter does not typically bind strongly with phosphorus. Organic matter covers fixation sites Organic matter reacts with free Fe and Al Organic matter competes for anion exch. sites Organic Matter tends to increase P availability Inorganic Soil Phosphorous Inorganic -Plant Available H2PO4- HPO4-2 (low) -Fe, Al bound -Calcium bound - Fixed on oxides Al(PO4) • H2O Ca3(PO4)2 H2PO4- Phosphorus is generally removed from solution by soil processes These processes have a finite capacity to retain phosphorus When the capacity is exceeded, phosphorus can become mobile. South Florida and Phosphorus Historic Flow Patterns Okeechobee and the Everglades Historic flow patterns in the Kissimmee – Okeechobee – Everglades system has been significantly altered, beginning in the late 1800’s. The design was to drain significant areas for agriculture and development and to prevent floodwaters from communities to the south and east. Development First Survey 1835 Buckingham Smith "The first and most abiding impression is the utter worthlessness to civilized man, in its present condition, of the entire region." In 1850, the Swamplands Act Passed Transferred 20 million aces to FL for drainage and reclamation Population: 87,445 1881 11 miles (17.7 km) of canal south of Lake Okeechobee towards Miami. Hamilton Disston Okeechobee north to Kissimmee and west to the Gulf of Mexico. 50,000 acres drained 1904 Broward Elected “pestilence-ridden swamp” Empire of the Everglades 1905 Everglades Drainage District Authorized Canals, taxes By 1920, 4 major canal systems linked Okeechobee to the Atlantic, Began in 1881 By 1920 Melaleuca Tree 1906 Invasive ornamental 6-12 ft. growth per year displaces native vegetation 359,000 acres Florida East Coast Railway WWI 1914-1918 Tamiami Trail 1911 Flagler 1928 1928 Belle Glade Hurricane 135 mph winds 20-foot deep floodwaters South of Okeechobee 3000 to 8000 dead After the storm Hoover Dike 19 water control structures 45 feet high and 150 feet wide 143 miles of levee Drainage Former extent of Kissimmee Basin and floodplain Hoover Dike (1932) Everglades Agricultural Area (EAA) Perimeter Levee (1954) Water Conservation Areas (management of flow) To Atlantic To Gulf Historic Current EAA Phosphorus loading to S. Florida Ecosystem Dairy/Beef Inputs North and South of Okeechobee Crop Production Kissimmee Basin Crops: Everglades Agricultural Area EAA Sugar, Rice, Veg. 700,000 ac EAA 1940’s thousands of acres converted to agricultural production 1959 Cuban exiles established sugar plantations 1960s Sugar production increased 4-fold Sugar Today, sugarcane production contributes two-thirds of the economic production of Everglades agriculture, and uses nearly 80% of the crop land in the EAA Sugar and vegetable production contributes phosphorus to the ecosystem primarily through fertilizers and to a lesser extent through decomposition of plants. 382,000 acres 46% U.S. Palm Beach, Glades, Hendry Phosphorus Fertilization (lbs/ac) V. High Soil P Low Soil P Celery 260 200 140 80 20 0 0 0 0 Endive 200 175 150 125 100 75 50 25 0 Escarole 200 175 150 125 100 75 50 25 0 Lettuce (Head) 200 175 150 125 100 75 50 25 0 Radish 100 40 0 0 0 0 0 0 0 Romaine 200 175 150 125 100 75 50 25 0 Sugar Cane 120 100 80 40 20 0 0 0 0 Phosphorus loading to S. Florida Ecosystem Dairy/Beef Inputs North and South of Okeechobee Agriculture Kissimmee Basin Dairy and Beef In 1521 Ponce de Leon brought horses and cattle to Florida, making it the oldest cattle raising state in the country. No other part of our country had cattle until the Pilgrims brought cattle in the early 1600's Florida's ranchers now raise the third largest number of cattle of any state east of the Mississippi Kissimmee drainage basin 12,000 km2 (1947) Phosphorus Solid Manure: 5.5 g / kg total Phosphorus One cow can excrete between 40 and 60 g of phosphorus per day Subject to movement via runoff, stream flow, soil water movement, and groundwater movement Cattle and Dairy Okeechobee, Highlands, and Glades Counties: 328,000 head (19% of total) Okeechobee County is ranked number one for all cattle in the state Kissimmee – Okeechobee - Everglades The Lower Kissimmee River Basin is among largest sources of external phosphorus loading to Lake Okeechobee The Kissimmee river alone contributes about 20% of the phosphorus flowing into Lake Okeechobee Okeechobee, in turn, is a source of phosphorus to the Everglades Surface Water Improvement Management Act: SWIM (1987) Mandates phosphorus load level of 397 tons/yr Clean Water act: 154.3 tons per year deadline of January 1, 2015 SWIM Plan priority basins Lake Target level of 40 ppb in Lake Okeechobee Some Strategies The Dairy Rule (1987) creating lagoons to capture and contain dairy waste Implement Best Management Practices (BMPs) buffer areas around places animals congregate, eliminating phosphorus fertilization near tributaries, reducing phosphorus imports in animal feeds, reducing animal density Works of the District Rule permits are required for all discharges into waterways Dairy Buy-Out Program to facilitate removal of animals from dairies not able to comply 19 of 45 Dairies Remain Above SWIM target (tons) Phosphorus Loads to Okeechobee Above Target SWIM target: 397 tons 2007: 146 ton reduction of P entering Okeechobee 2007: 146 ton reduction of P entering Okeechobee The target level is 40 ppb. Phosphorus concentrations in the Lake remain at about 117 ppb Internal Loading Two Sources Decomposition of submerged aquatic vegetation releasing phosphorus back into the water column Dissolution of compounds in sediments which bind and store phosphorus. Internal Loading Phosphorus and Iron Phosphorus has a strong affinity for iron FePO4 Solid Precipitate Readily incorporates into bottom sediments Internal Loading Fe high oxygen Fe low oxygen Dissolved phosphorus combines with oxidized iron (Fe3+) to create 3+ 2+ an insoluble compound that becomes buried in lake sediments. Simplified: Fe3+ + PO43- = Fe(PO4) solid If oxygen contents are reduced (anoxic bottom sediments) the converts to Fe which solubilizes the compound returning P to water. Fe 3+ 2+ 2+ Fe (PO4) 3- to water P released by sediments is taken up by photosynthetic algae faster than it can be returned to the sediments Lake Okeechobee Action Plan Developed by the Lake Okeechobee Issue Team December 6, 1999 RECOMMENDATION – Control Internal Phosphorus Loading. Phosphorus-rich mud sediments need to be removed from the lake to the maximum extent that is practical, in order to reduce internal phosphorus loading. Unless this internal loading is substantially reduced, it may take as long as 100 years for the lake to respond to watershed phosphorus control programs. Lost Lands Former extent of Kissimmee Basin and floodplain Hoover Dike (1932) Everglades Agricultural Area (EAA) Perimeter Levee (1954) Water Conservation Areas (management of flow) To Atlantic To Gulf Historic Current EAA Crops: Everglades Agricultural Area EAA Sugar, Rice, Veg. 700,000 ac Florida to Buy Out Sugar Land for Everglades Restoration WTVJ NBC 6 June 25, 2008: WEST PALM BEACH, Florida -- The largest U.S. producer of cane sugar, U.S. Sugar Corp., would close up shop in a $1.75 billion deal to sell its 292 square miles of land to Florida for Everglades restoration, the company president and Florida Governor Charlie Crist said Tuesday. The deal, announced at a news conference at the Arthur R. Marshall Loxahatchee National Wildlife Refuge, allows the state to buy U.S. Sugar's holdings in the Everglades south of Lake Okeechobee, the heart of the wetland ecosystem. 186,000 acres Organic soils possessing high natural fertility Historically flooded Water restricts the movement of oxygen The diffusion of oxygen through water is about 1000 times slower than diffusion through air Flooded Marsh Under flooded conditions, oxygen levels tend to be low Organisms? Aquatic Plants Die Heterotrophic microorganisms decompose tissues Aerobic heterotrophic organisms use oxygen Oxygen becomes depleted in water; it cannot diffuse fast enough to support aerobic heterotrophs Anaerobic heterotrophs become dominant Anaerobic Heterotrophic Organisms Can use energy stored in complex carbon compounds in the absence of free oxygen The energy is obtained by exchanging electrons with elements other than oxygen. Nitrogen (nitrate) Sulfur (sulfate) Iron (Fe ) 3+ Anaerobic respiration is less efficient and produces less energy. C H O + 6O2 → 6CO + 6H O 2880 kJ 6 2 2 C H 12 6 3NO3- + 3H O = 6HCO + 3NH O+ C6H12O6 + 3SO42- + 3H = 6HCO 3- + 3HS 4+ 2 1796 kJ 453 kJ 6 12 6 + 3- - Therefore, anaerobic decomposition is much slower than aerobic decomposition. Flooded Soils anaerobic decomposition of organic matter is much slower than aerobic decomposition. Organic matter is added to the soil faster than it can be decomposed by microorganisms Accumulation of organic matter at the soil surface additions Losses (CO2) Organic matter limestone Buildup of Organic soils Organic matter decomposes slowly when submerged in water. (anaerobic decomposition) Soils throughout the glades historically have been submerged. (anaerobic conditions) Led to vast amounts of organic matter accumulation, sometimes >10 ft. thick. Organic matter continues to accumulate as long as flooded conditions persist. Drainage Drainage exposes soils to oxygen and decomposition by aerobic heterotrophic organisms which can more efficiently decompose organic matter EAA Drainage Losses (CO2) additions Conversion from anaerobic to Aerobic decomposition (much more efficient) C6H12O6 + 6O2 → 6CO2 + 6H2O Losses of organic matter by decomposition exceed new additions – soils disappear Subsidence of Organic soils up to 10 feet 1912 to 2000 Public Funding Issues Revisited in State’s Buyout of U.S. Sugar South Florida Business Journal - by Paul Brinkmann a bill in the Florida Senate that would require voter approval of any certificates of appreciation (bonds) issued by water districts. Restoration of More Natural Flow Regimes Comprehensive Everglades Restoration Plan restoration, preservation, and protection of the South Florida ecosystem recover and sustain those essential hydrological and biological characteristics that defined the original pre-drainage Everglades interconnected and interrelated wetlands provide for water supply and flood protection reestablishment of native plant communities Low levels of nutrients Next: Phosphorus and South Florida ...
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This note was uploaded on 07/31/2011 for the course SOS 3022 taught by Professor Staff during the Fall '08 term at University of Florida.

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