Transcript Phosphorous - University of Florida

Phosphorous
Organic Phosphorous
Components of soil organic matter and plant tissue
Phosphate sugars
Nucleic Acids (DNA/RNA)
ATP
Phospholipids
ATP
Importance
Essential Macronutrient
Limiting Resource
Present in Fertilizers, animal wastes, wastewater
Availability can be very limited
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
Inorganic
PO4-3
(Orthophosphate)
H3PO4
H2PO4-
HPO4-2
The form of available phosphorus is pH-dependent
Plant Availablity
H2PO4
-
Most Available
HPO4-2
pH 6-8
pH 3-6
pH 8-11
Optimum pH = 6.5 for mineral soils
Acidic Soils
Acid Soils (Low pH)
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
Form of available P at low pH: H2PO4-
(pH 3-6)
H2PO4- combines with free Al3+ and Fe3+
(Insoluble)
Al3+ + H2PO4- + 2H20 = Al(OH)2H2PO4 + 2H+
simplified
Al3+ + PO4-3 = Al(PO4)
Al(PO4) • H2O
Variscite
Basic Soils (High pH)
Calcium Binding in Basic Soils
CaCO3
(higher calcium availability)
H2(PO4)- is the available form of P
CaCO3 + 2H2(PO4)- = Ca [H2(PO4)]2 + CO32CaHPO4
Ca5(PO4)3OH (Apatite mineral)
Availability and pH
Formation of insoluble solids
Low pH
Aluminum and Iron
phosphates
High pH
Calcium Phosphates
Reaction with Soil Minerals
Fixation on Iron and Aluminum
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
OH
OH
Fe
Fe
OH
H
(PO
)
+ 2
4
H2(PO4)FE
Fe
OH
OH
+
OH-
OH
O-
Fe
OH
+
O-
P
OH
Fe
OH
OH
OH
O-
O-
P
Fe
Fe
OH
OH
OH
Coatings on Sands and Silicate Clays
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
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
Escarole
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
Fe3+ high oxygen
Fe2+ low oxygen
Dissolved phosphorus combines with oxidized iron (Fe3+) to create
an insoluble compound that becomes buried in lake sediments.
Simplified: Fe3+ + PO43- = Fe(PO4)
solid
Fe3+
If oxygen contents are reduced (anoxic bottom sediments) the
converts to Fe2+ which solubilizes the compound returning P to water.
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 (Fe3+)
Anaerobic respiration is less efficient
and produces less energy.
C6H12O6 + 6O2 → 6CO2 + 6H2O
C6H12O6 + 3NO3- + 3H2O = 6HCO3- + 3NH4+
C6H12O6 + 3SO42- + 3H+ = 6HCO3- + 3HS-
2880 kJ
1796 kJ
453 kJ
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
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