The Methods Used to Prevent Eutrophication by Limiting the Transport of Phosphorus from Agricultural Non-point Sources

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The Methods Used to Prevent Eutrophication by
Limiting the Transport of Phosphorus from
Agricultural Non-point Sources
Presented by Austin Omer
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Objectives

• Look at how the hydrologic cycle effects
  phosphorus input into fresh water from
  agriculture non-point sources
• Review the Best Management Practices (BMPs) and
  identify the most efficient methods for
  preventing eutrophication

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Eutrophication

• Eutrophication is the increase of organic matter
  in fresh waters (Nixon 1995)
• Occurs naturally or is caused by man
• Occurs because of an excess of nutrients (N and
  P) being available for growth

• Phenomena caused by Eutrophication
• Increase aquatic plant growth
• Oxygen depletion
• pH variability
• Plant species quality effects
• Food chain effects
• Toxic algal blooms
• Collapse of sensitive fish populations
• (Sharpley 1994 Reynolds and Peterson 2000)

http//drake.marin.k12.ca.us/stuwork/rockwater/Eut
rophication/index.html
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http//oceanservice.noaa.gov/education/kits/estuar
ies/media/supp_estuar09b.html
Economic Impacts Eutrophication can restrict
the use of surface waters for aesthetics,
fisheries, recreation, industry, and drinking
http//www.lakescientist.com/learn-about-lakes/wat
er-quality/eutrophication.html
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Phosphorus

• Nitrogen, Carbon, and Phosphorus are all required
  for plant and algal growth
• Difficulties in controlling N and C air-water
  exchange and fixation of N2 by blue green algae
  result in P being the nutrient that promotes
  eutrophication (Sharpley 1994)
• Phosphorus is the main limitation of primary
  production in freshwater systems (Schindler 1977)

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(Dinnes 2004)
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Non-point vs Point Sources

• Non-point Sources
• Does not have one specific source
• (ex) fertilizing a lawn or agricultural field
• More difficult to monitor and regulate

• Point Sources
• Comes from a single source
• (ex) factory or waste water treatment facility
• Less common due to the Clean Water Act of 1972

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http//www.caes.uga.edu/Publications/displayHTML.c
fm?pk_id7173
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Agricultural Non-point Sources of Phosphorus

• Fertilizers (most commonly P2O5)
• Organic Manure
• Inputs from Grazers
• Plant residues
• (Jennings 2003)

• Forms of Phosphorus lost
• Dissolved P
• is desorbed, dissolved, and extracted from soil,
  crop residues, surface applied fertilizer or
  manure
• Immediately ready for biological uptake
• Sediment P
• this includes P in soil particles and organic
  material eroded during flow events
• sediment P accounts for about 80 of P
  transported in runoff from most cultivated land
  (Sharpley 1992)

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Loss from Agriculture Non-point Sources
Dissolution Losses (ex) solid P is transformed to
liquid Incidental Losses (ex) application after
rainstorm event Physical Losses (ex)
erosion Agriculture runoff has been estimated
to cause impairment to 55 of rivers and 58 of
lakes surveyed that have water quality problems
(USEPA 1990).
(Haygarth and Jarvis 1999)
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Hydrologic Cycle
Pathway by which P enters fresh water sources.
(Sharpley 2003)
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Management

• Source Management
• Controlling the amount of P applied in inorganic
  fertilizer or by controlling P in feed consumed
  by livestock to reduce P concentrations within
  manure
• Tries to achieve a minimal level of P build up in
  soils above the levels needed for optimal crop
  growth

• Transport Management
• Reduces P loss by preventing erosion, surface
  runoff, and subsurface runoff
• More efficient at reducing sediment P than
  dissolved P (Sharpley 2003)
• Tries to reduce the impact of rainfall on soil
  surface by reducing runoff volume and velocity,
  increasing soil resistance to erosion, and
  trapping sediment to prevent erosion (Gillingham
  and Thorrold 2000)

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(Jennings 2003)
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Source Management

• In most cases an increase in the application rate
  of fertilizers and manure increased P loss
  (Romkens and Nelson 1974)
• Nutrient management by controlling the amount of
  P applied to fields was found to be an effective
  measure for controlling P loss (Sharpley 2006)
• Source BMPs are one of the most effective ways to
  reduce P from non-point sources (Sharpley 2004)
• There are other factors that play a role in
  nutrient loss such as application rate, season,
  location, amendments, and composting manure

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Critical Source Areas
Source management by reducing application of
fertilizer to critical source areas has the
potential to greatly reduce P loss (Sharpley
1994).
(Sharpley 2003)
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Transport Management by Preventing Overland Flow
and Erosion

• Includes
• Increasing vegetation cover by conservation
  tillage
• Buffer strips
• Riparian zones
• Terracing
• Contour tillage
• Cover crops
• Impoundments
• Reservoirs (settling basins)

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(Sharpley 2009)
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Transport Management by Preventing Leaching and
Interflow

• Ryden (1973) found that phosphorus enrichment of
  surface waters may be caused by a significant
  amount of interflow
• Bolton (1970) found that subsurface flow of P
  export equaled or exceeded overland flow
• Interflow has become a more intense transport of
  nutrients due to the increase in use of
  artificial drainage systems

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Artificial Drainage Systems

• Ways to reduce P loss by artificial drainage
  systems
• Prevent leaching by maximizing plant uptake and
  minimizing P inputs (source management)
• Removing P loss after input to artificial
  drainage systems can be accomplished by the
  following
• Diverting to constructed wetlands
• Removal of sediment
• Chemical treatment to fix P to insoluble forms
• Stream biochemical filters
• (Sims 1998)

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Conclusions

• And integrated approach of both source and
  transport management may provide better
  prevention of P loss
• Further research into the remedial strategies to
  help prevent further eutrophication should be
  investigated to improve water quality
• Research into the affect of subsurface tiles as a
  pathway for P loss as well as the atmospheric
  deposition of P is needed

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