Title: The Methods Used to Prevent Eutrophication by Limiting the Transport of Phosphorus from Agricultural Non-point Sources
1The Methods Used to Prevent Eutrophication by
Limiting the Transport of Phosphorus from
Agricultural Non-point Sources
Presented by Austin Omer
2Objectives
- 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
3Eutrophication
- 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
4http//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
5Phosphorus
- 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)
6(Dinnes 2004)
7Non-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
8http//www.caes.uga.edu/Publications/displayHTML.c
fm?pk_id7173
9Agricultural 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)
10Loss 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)
11Hydrologic Cycle
Pathway by which P enters fresh water sources.
(Sharpley 2003)
12Management
- 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)
13(Jennings 2003)
14Source 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
15Critical 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)
16Transport 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)
17(Sharpley 2009)
18Transport 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
19Artificial 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)
20Conclusions
- 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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