Transcript Slide 1

The Methods Used to Prevent Eutrophication by
Limiting the Transport of Phosphorus from
Agricultural Non-point Sources
Presented by: Austin Omer
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
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
http://drake.marin.k12.ca.us/stuwork/rockwater/Eutrophication/index.html
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://oceanservice.noaa.gov/education/kits/estuaries/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/waterquality/eutrophication.html
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)
(Dinnes 2004)
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
http://www.caes.uga.edu/Publications/displayHTML.cfm?pk_id=7173
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)
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)
Hydrologic Cycle
Pathway by which P enters fresh water sources.
(Sharpley 2003)
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)
(Jennings 2003)
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
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)
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)
(Sharpley 2009)
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
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)
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
References
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