Understanding Lawn Phosphorus Runoff

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Understanding Lawn Phosphorus Runoff

• Dr. John Stier
• University of Wisconsin-Madison
• Dept. of Horticulture

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Runoff

• Definition Water that is discharged laterally on
  or through the ground
• Surface runoff
• Seepage flow from ground water
• Both Runoff Volume and Contamination must be
  considered
• Concentration level has little impact if only few
  ounces or quarts runoff from large area

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Runoff Depends on

• Rate of precipitation/irrigation
• Pre-existing soil moisture
• Slope
• Infiltration percolation capacity of soil
• Soil type (sand gt loam gt clay)
• Time of year (frozen vs. unfrozen)
• Vegetation height and density

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Need for Nutrients

• 413 uptake
• N is ephemeral, new additions needed
• Most P recycled once in plant
• Soils have sufficient P, K for most of growing
  season
• Exceptions
• New establishment
• Cold weather
• Root rots
• Some soils low P

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Need for Nutrients

• Dense turf reduces runoff
• Volume
• Sediment
• Dissolved nutrients

Poorly fertilized
Well fertilized
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Phosphorus is Phosphorus

• Natural sources (Compost, sewage, etc.)
• Low NP ratio, e.g., 6-2-0
• If apply 1 lb N/1000 ft2, then 0.33 lb P2O5
• If use 25-3-4 then only 0.12 lb P2O5

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How Our Environment Has Changed

• Impervious vs Pervious surfaces
• Pre-Development Forests, Fields, Wetlands
• Post-Development Rooftops, driveways, sidewalks,
  streets, parking lots
• Post-Development Lawns, Rain Gardens, Ditches,
  Detention Ponds
• Stormwater fees

8
Problems with Runoff

• Sediment
• Deposits in surface waters, sewers, etc.
• Carries adsorbed chemicals nutrients (P)
• Nutrients
• N P
• Algal blooms oxygen deprivation

9
Phosphorus in Soil

• 200 2000 lb P/Acre in soil
• 100 1000 ppm or 0.01 to 0.1 of soil mass
• Tightly bound to soil, Fe, Al, Ca, Mg
• 20-80 soil P is organic (Brady Weil, 1996)

Only 0.01 of P is available for plant
uptake (0.02 to 0.2 lb P or 0.01 to 0.1 ppm)
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Phosphorus Sources in Runoff

• Organic sources
• Pollen, seeds
• Leaves (living and dead)
• Animal waste
• Manure spread on frozen fields
• Wildlife
• Waterfowl 27 new P in NC lake (Wambach
  Mallin, 2001)
• Mississipi Flyway now 1.4 million geese with 6
  annual increase
• 100 avg geese 5.3 oz P/day (Sherer et al.,
  1995) 5x gt storm drain P in NE urban lake (Moore
  et al., 1998)
• Pets Avg dog 2.6 lb P2O5/yr
• Aquatic animals/plants

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Phosphorus Sources in Runoff

• Inorganic sources Soil particles/dust
• Bare/exposed soil
• Agricultural operations
• Building construction
• 8.6 tons sediment/12.1 lb P/A/yr in WI (Daniel et
  al., 1979)
• Geography of area
• Deicing agents
• MDOT (1993) 14-26 ppm P
• New York Ag Dept. salt-sand mixes 55-163 ppm P

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The Scientific Method

• Observe a condition
• Read existing information
• Develop theory
• Test theory
• Accept, reject, or alter theory

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Multiple Runoff Studies Conducted

• 1970 current
• Water quantity, nutrients, pesticides
• Crops, turf, fields/prairies

Runoff plots at UW-Madison
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Sediment in Runoff from Crops, Turf, and
Grasslands
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Phosphorus in Runoff from Crops, Turf, and
Grasslands
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Fertilization Effect on Phosphorus Losses from
Lawn Turf
Source Kussow, 1997
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Seasonal Effects on Runoff
Frozen soils Non-frozen soils
2003-04 Dane County Wisconsin
lb P / acre
Prairie 0.65 0.07 Turf 0.58
0.02
Steinke et al., 2007, J. Environ. Qual.
36426-439.
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Tree Leaf Phosphorus

• P in street runoff (Waschuch et al., 1999)
• Madison, WI
• No trees lt0.1 ppm P
• 80 tree canopy 0.8 ppm P
• Weekly street sweeping ? P runoff by 42 (Shapiro
  and Pfannkuch, 1973, Univ. Minn.)

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Key Points

• Baseline levels of P exist
• Sediment, animal, atmospheric deposition
• Paved areas/drains funnel runoff to lakes
• Scientific data do not show lawn fertilizers add
  P runoff
• Turf cover no sediment loss
• Existing models based on bare ag soils
• 80 of lawn runoff occurs during winter thaw
• Natural P not better than synthetic sources
• Underfertilization will increase runoff volumes
  and P amounts