1. science
2. ecology
3. pollution

What is the Risk to Runoff Water Quality Posed
by Fertilization of Turfgrass?
Dr. Chris Murray,
Department of Interdisciplinary Studies
Outline
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What motivated this project?
Runoff and pollution
Turfgrass as a water quality management tool
The problem: excess nutrients
Experiments and studies of the effect of
fertilization
• Best Management Practices
• Conclusions
Project motivation
• A collaboration between Landscape Ontario’s
Lawn Care Commodity Group and Lakehead
University
• Two factors initiated this project:
1. Source water protection agencies and similar
organizations are considering fertilizer bans as a
means of protecting water quality
2. Several studies had reported results
contradicting this approach: where fertilizer is
stopped, N,P in runoff increases
Why might this be a problem?
• As was the case with pesticide use, fertilization of
lawns is often cited as a purely cosmetic practice
• While lawns provide aesthetic and recreational
value, these benefits are considered nonessential
• Much more emphasis is placed on the risk of
water contamination than these “soft” benefits
of turfgrass
• If there is little or no value and significant risk,
why not ban fertilizers and eliminate that risk?
• Is this a quantitatively appropriate response?
What do I mean by quantitative?
• Not all situations require numerical
information to make an informed decision
• Example: how much gasoline should I drink in
a day?
• There is no benefit to drinking any amount of
gasoline
• Answer: don’t ever drink gasoline!
• Don’t need to consider body weight, age, or
any other quantity to make this decision
Another example
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How much water should I drink every day?
Q: Can you drink too much water?
LD50 in rats: 90 g/kg
A: Yes.
Q: Do I need to drink any water?
A: Yes, at least 2 L a day
So, drink somewhere between 2 and 10 L
Numbers are important to consider, because
there are competing factors
Turfgrass Fertilization
• How much should one fertilize a lawn to
obtain the best water quality?
• Q: Can you reduce water quality by fertilizing
too much?
• A: Yes.
• Q: Can you improve water quality by
fertilizing?
• A: Yes.
Risks of ignoring competing factors
• If fertilization can improve water quality,
restricting fertilization can damage water
quality
• Ignoring impact on turfgrass management
industries, the implication is that such
regulation could achieve the opposite of its
intended effect
• Even in Canada, we cannot afford to make
very many mistakes where water quality is
concerned
General research questions
• What is the true state of scientific information
regarding this issue?
• Is there consensus within the scientific
community?
• If so, does it support a ban on fertilization of
turfgrass?
• A primary focus of this study is the effect,
both positive and detrimental, fertilization of
turfgrass may have on the nutrient pollution
through runoff.
Stormwater / runoff
• My background: stormwater and wastewater (not
biology, ecology or turfgrass science)
• Most critical to understand: what dominates
water pollution
• Why is runoff a problem?
• Runoff is “natural”, and would exist without
human intervention
• Human activity dramatically increases runoff and
the pollution it carries.
• As runoff increases, pollution increases
From SUNY College of
Environmental Science
and Forestry
Clean water is pollution
• What?
• How do stormwater management devices
work?
• Quality: Sedimentation, filtration, sometimes
chemical absorption
• Quantity: Dry wells, ponds, detention tanks
• Simple example: gravity separator
Velocity the same all along pipe, little settling occurs.
Pollutants in = pollutants out
Velocity reduced in expanded section
More time to settle, bigger particles drop faster
Slower flow, bigger tank = more captured, less pollution
“Self-cleaning” pollution traps
Scouring: high-velocity water stirs up sediment and
resuspends captured pollution
Pollution out > pollution in
Too much water is pollution,
even if it is pure.
Reduced runoff = reduced pollution
Combined Sewer Overflow
Photo credit: Christopher Zurcher
Experimental considerations
• Need to measure quantity and quality
• Apples-to-apples comparison requires
measurement of input as well as output
• Difficulty measuring small volumes introduces
bias
• A mass balance approach is needed: what are
all the paths nutrients may follow?
Bias
• Large events are easy to measure, carry more
pollution
• If you don’t measure small events, you may
skew results towards higher pollutant count
• Many small events can account for more
pollution than a few large events, in total
• Small amounts of runoff stretched out over
long periods of time are difficult to measure
“Laboratory” vs. Field
Experimental plot
Real lawns
• Controlled fertilization
• Controlled rainfall
• Events observed by
researchers
• Can characterize all
input/output water and
nutrients
• Unrealistic
• Always includes worst
case scenario
• Realistic
• Not as controlled
• May rely on
assumptions such as
homeowner behaviour
• Relies on automatic
samplers
• Realistic rainfall, lawn
use
From Yu et al., J.
Hydrology, 434-435
(2012) p.1-6
From Garn, USGS
Water Investigation
Report 02-4130
(2002)
Nutrients
• Macronutrients required by
turfgrass:
• H2O, CO2, O2
• Nitrogen (e.g. as NO3-)
• Phosphorous (e.g. as H2PO4-)
• Potassium (K)
• Calcium (Ca)
• Magnesium (Mg)
• Sulphur (S)
of
Nutrient Cycles, Role in Department
plants
Geology, University
• Nitrogen:
of Illinois
– Ingredient in proteins, DNA, chlorophyll, etc.
– Affects shoot-root growth, density, color, disease
resistance, and stress tolerance.
• Phosphorous:
– Ingredient in cell membranes, energy transfer
molecules, DNA, etc.
– Affects rate of seedling development and root growth.
• Why are these of primary concern?
Algal Blooms, Eutrophication
From Ministry of the Environment , Northwest Pacific Region Environmental Cooperation Center
Terminology
• Surface water/stormwater/runoff
• Infiltration/leachate
• In general, we aim to increase infiltration and
decrease runoff to decrease pollution
• Why?
• Sediment and associated chemical pollutants
Erosion
• Wherever
development
occurs, risk of
increased runoff
velocity and
erosion
• More sediment is
carried into water
Dissolved/particulate pollution
• Nutrients such as phosphorous are soluble in
water, but will bind with minerals in sediment
• A very small concentration of sediment may
be responsible for most of the nutrient
loading
• For a given mass, fine particles carry more
pollution than large particles, and carry it
further
How can adding fertilizer help?
• Turfgrass is, in general, a non-native groundcover
that requires maintenance to thrive
• Without human intervention, it will not
outcompete indigenous plants (weeds) which are
better-suited to harsh conditions (especially
drought) but not suited to human-scale runoff
• In general, healthier turfgrass increasingly
reduces runoff and increases
infiltration/evapotranspiration
• Runoff can be completely eliminated by turfgrass,
and a lawn is often the only barrier between
impervious surfaces and waterways
Runoff, Infiltration and Erosion Control
• How might reducing fertilizer increase the
concentration of N, P in water?
• Small effect: increased decay of plants
• Large effect: less healthy turfgrass cannot hold
water as effectively, so runoff increases
• Filtering is not enough: the amount of water
must be reduced
Competing Factors
• The contamination of runoff by nutrients
(both dissolved and particulate) found in
fertilizer contributes to eutrophication of lakes
causing negative impacts on the aquatic flora
and fauna.
• Healthier turfgrass systems improve surface
water quality through natural filtration and
absorption of water, which reduces runoff
intensity.
Summer/Fall 2012 Review
• More than 150 articles
• Aim: collect every piece of information
regarding the impact of turfgrass fertilization
on water quality
• Examined turfgrass versus alternative
groundcovers
Some simple questions
• Under controlled conditions, what is the effect
on the amount of nutrients output due to
fertilization of turfgrass?
• What evidence is there turfgrass is a good
choice for limiting runoff?
• What recommendations might be made,
based on scientific consensus (if one exists)?
Reports worth examining
• Garn, 2002:
– No runoff other than that due to rain on lawns
– Increase P in runoff for fertilized lawns
– The site with the best turf stand had the least runoff,
though quantitative measurements not made.
– No effect of fertilization on nitrogen in runoff
• Kussow, 2002, 2004, 2008:
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Fertilization with P leads to more P in runoff
Accounted for runoff volume
Most (runoff, nutrients) recorded when soil frozen
Without fertilization for two years, runoff, nitrogen and
phosphorous increased
– Whether soil is frozen is dominating factor
• Easton and Petrovic, 2004
– Examined both synthetic and organic fertilizer
– P losses higher from P-containing fertilizer, highest
for organic types (P applied very high)
– Fertilization increased infiltration, decreased
runoff
– Frozen soil runoff accounted for majority
– Fertilization during establishment created most
pollution
– In many cases, equal or higher N,P losses from
unfertilized control due to overall increased runoff
• Soldat and Petrovic, 2008
– Review of various studies of runoff versus
fertilization
– Worst-case scenario studies where water is added
to plots following P fertilization showed P in runoff
directly related to P applied
– Realistic rainfall events yielded results that
included higher P from non-fertilized sites
– Sediment loss from turfgrass very low, or zero
• Beirman et al., 2010
– Examined no fertilization, P-free, P and triple-P
fertilization
– Runoff highest for non-fertilized plots
– P in runoff from non-fertilized site highest in year
1, the same as from site receiving P in fertilizer in
subsequent four years
– Frozen soil runoff dominates P loading, and
recommended that no P used in Fall where runoff
potential is high
Overview
• No studies perfectly controlled, perfectly realistic,
but…
• Usually, nutrient concentrations in runoff higher
where fertilization is applied
• Usually, amount of runoff is lower where
fertilization is applied
• Most often, the total nutrient loss in runoff is
decreased by fertilizing
• Where applicable, nutrient loss when ground is
frozen dominates annual pollution
Turfgrass vs. other vegetative
groundcovers
• Comprehensive studies are lacking.
• Most lawn alternatives are composed of nonnative ornamental plant species
• The use of turfgrass reduces yearly runoff
volume much more than native grass species
• Much more nitrogen may be leached from
ornamentals than turfgrass
Best Management Practices: timing
• Worst: fertilization before the rain
• Avoid fertilization when soil is going to
freeze or is already frozen
• Frequent, small applications better
Design
• Avoiding soil disturbance, or limit
disturbances to one area at a time, always
with turfgrass separating it from the
waterways
• Avoid fertilization of turfgrass on high silt or
clay content soil near the bottom of hills, near
water’s edge
Clippings
• Mow at high cut height, frequently and when
grass is dry
• Leaving clippings can greatly reduce runoff,
but contributes (as much as 50% of required)
nitrogen (though not phosphorous)
• As with any nutrient source, keep clippings
away from impervious surfaces where they
may be washed away
Watering
• Irrigate in the morning
• Watering in recommended, as long as there’s no
runoff
• Water pollution is less likely with more frequent,
smaller volumes of watering… there is less
likelihood of runoff.
• Another issue of competing factors? Better roots
are supposed to be supported by the infrequent,
high-volume watering, and these will reduce
runoff… but short-term increased runoff
• Research lacking on effect of irrigation
Monitoring
• Every three years, soil test for P
• Until a test can be performed, use P-free
fertilizer
• Especially during establishment, monitoring of
soil needs is important
• Some reasons why soil testing is not enough:
soil levels do not determine runoff potential
• Need to also measure: bulk density of soil,
compactness
Conclusions
• The majority of studies examining the effect of
fertilization on turfgrass show reduced runoff
(and reduced nutrient loading) when lawns
are fertilized
• Turfgrass is more effective than most
alternative groundcovers
• Frozen soil, like any impervious surface,
increases runoff potential and can be
responsible for most of the pollution
Take-away’s
• Too much water (even when clean) is pollution
• Development
= impervious surfaces
= high volume, high velocity runoff
= erosion
= pollution
• Turfgrass (which is improved by careful
maintenance) is one of the only “band aids”
we have to treat this problem
Acknowledgements
• Student researchers:
– Kayla Snyder, Diane Mitchell, Lindsey Jaanussen,
Brooke Marion, Kristyn Madrick
• Thanks to Mr. Ken Pavely, Mr. Gavin Dawson
and Landscape Ontario’s Lawn Care
Commodity Group
Thank You!
For more information contact:
Dr. Christopher Murray
Department of Interdisciplinary Studies
Lakehead University
[email protected]