Lawns, Lakes, and Laws

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Lawns, Lakes, and Laws
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PhosphorusP

• Needed plant nutrient
• Most rare of the major life building
  blocks (C, H, O, N, P, S)
• 75 of nations use is mined in Florida

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PhosphatePO4

• Phosphorus is highly reactive
• Does not exist as an element in nature
• Combines with oxygen to form phosphate

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Phosphorusand plants

• Function Energy transfer and cell division
• Deficiency Stunted growth
• Deficiency Purple or yellow leaves
• Deficiency More common in cool spring

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Phosphorusand plants

• Function Energy transfer and cell division
• Deficiency Stunted growth
• Deficiency Purple or yellow leaves
• Deficiency More common in cool spring

RARE!
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Phosphorus in soil
300 lbs/acre


Pools of phosphorus storage in soil
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Phosphorus in soil

• Soil solution phosphorus (H2PO4-)
• Form taken up by plants
• Mobile form
• Small fraction of total soil P (

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Phosphorus in soil

• Active soil phosphorus
• In equilibrium with solution P
• 300 lbs/acre
• Tightly adhered to soil particles

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Phosphorus and soil pH
7.0 pH
6.0 pH
Availability of phosphorus vs. soil pH
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Phosphorus fertilization

• Recommended on turf when
• Solution P Soil P

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Phosphorus and lakes

• Most limiting plant nutrient in lakes
• Algae blooms low oxygen and smell
• 1 lbs P 300 lbs to 500 lbs algae

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Impacts of phosphorus
High growth
Low light
Low oxygen
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Speeding aging of lakes
10,000s YEARS IN NATURAL CONDITIONS
10s to 100s YEARS UNDER HUMAN INFLUENCE
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Tropic State
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A factor of 1,000 less!
60 parts per BILLION
30 parts per MILLION
It takes a 1,000 times less phosphorus to turn a
lake green than keep a lawn healthy
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As phosphorus goes up, algae goes up, and water
clarity goes down
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Secchi Disk Secchi disk is a low-tech way to
measure water clarity and determine a lakes
tropic state
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Experimental Lake Area Study(Fisheries and
Oceans Canada)

• Top-to-bottom curtain divides lake in two
• Carbon and nitrogen added to one side
• Carbon, nitrogen and phosphorus added to
  other effect is clear to see

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Sources of phosphorusWhen it rains, it pollutes
Think watersheds!
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Typesof runoff pollution

• Sediment soil erosion, street grit
• Nutrients nitrogen and phosphorus
• Organics manure, leaves, grass
• Toxics lead, zinc, copper, pesticides

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Impervious surfaces
Residential Areas 50 Impervious
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Every city lot is waterfront property!
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Sources of phosphorus runoff
Bannerman - Wisconsin DNR
Sidewalks
Roofs
Driveways
Lawns
Streets
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Sources of phosphorus runoff from lawns
Soluble plant P
Soil solution P
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Sources of phosphorusrunoff from lawns

• Runoff from plant material (dissolved)
• Misapplied fertilizer (dissolved)
• Runoff from soil solution (dissolved)
• Attached to eroded soil (particulate)

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Sources of phosphorusrunoff from lawns
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• Runoff from plant material (dissolved)
• Misapplied fertilizer (dissolved)
• Runoff from soil solution (dissolved)
• Attached to eroded soil (particulate)

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Phosphorus runoff by land use
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Grass clippings

• Contain 0.13 lbs P / 1000 sq. ft. / year
• Thats 0.65 lbs P / ave. yard / year

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Controlling P runoff is package deal
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Phosphorus fertilization

• Apply according to soil test
• Important when seeding or sodding
• Rarely needed on est. lawns in Metro
• Sweep up overspread spilled material

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Reading the bag
Look for the middle number!N - P - K

• Given in phosphate by weight
• Phosphate (P2O5) not phosphorus (P)!
• P P2O5 2.29

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Takinga soil test

• Sample is made up of 10 sub-samples
• Collect with trowel and plastic bucket
• Sample 3 deep on establish lawns
• Sample 6 deep for new lawns

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• Sample front and back lawn separately
• Sample randomly, avoid odd areas
• Mix in plastic bucket send 1 pint to lab

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• Two phosphorus tests used in Minnesota based on
  soil pH
• Bray 1 pH 7.4
• Olsen pH 7.4

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Application challenges

• Selecting fert. with needed N-P-K balance
• 1,000 sq. ft.??? How big is my lawn?
• Setting spreader application rate
• Soil test? Calibrate? Get a life!!!

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The lawand the lawn

• State phosphorus lawn fertilizer law
• Local fertilizer ordinances
• Use vs. Sale regulation

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Minnesota phosphorus lawn fertilizer law

• Passed in 2002
• Goes into full effect in 2004
• Concerns phosphorus fertilizer - mostly
• Treats metro and non-metro differently
• First in nation - has drawn attention

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MN lawn fertilizer law

• Metro area (seven county) - Starts 2004
• 0 P2O5 fertilizer required, unless
• - Newly seeded or sodded lawn
• - Soil test shows need
• - Applied by trained golf course staff

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MN lawn fertilizer law

• Non-metro area - Starts 2004
• No greater than 3 P2O5 fertilizer
  required, unless
• - Newly seeded or sodded lawn
• - Soil test shows need
• - Applied by certified golf course staff
• Cities can opt to adopt 0 P2O5 limit

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MN lawn fertilizer law

• When liquid product is used in non-metro
  area, rate is limited to 0.3 lbs. P2O5 per
  1,000 sq. ft. - unless need for higher rates
  is shown.
• When there is need to apply phosphorus lawn
  fertilizer at higher rates, University of
  Minnesota recommendations are to be followed.

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MN lawn fertilizer law
Prohibited to apply fertilizer (any type) to
impervious surfaces. Examples Streets,
sidewalks, driveways. Started 2002
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MN lawn fertilizer law

• Preempts local ordinances on fertilizer use
• Allows pre-2002 local ordinances on fertilizer
  sales to stand
• Enforcement by local units of government as a
  petty misdemeanor

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City of Burnsville ordinance - before state law

• No application between Nov 15 - April 1
• Clean fertilizer from impervious surfaces
• Keep outside 20 foot buffer around water
• Apply no greater than 0 P2O5 fertilizer
  unless new lawn or soil test shows need
• Notice of law needs to be posted in stores

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City of Burnsville ordinance - after state law

• No application between Nov 15 - April 1
• Clean fertilizer from impervious surfaces
• Keep outside 20 foot buffer around water
• Apply no greater than 0 P2O5 fertilizer
  unless new lawn or soil test shows need
• Notice of law needs to be posted in stores

Locals can no longer regulate fertilizer use
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0 P2O5 fertilizers becoming widely available . .
.
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What to advise . . .

• On existing lawns
• - Use 0 P2O5 fertilizer unless a need
  for phosphorus is shown
• - Unless a new lawn, soil testing is
  easiest way to show phosphorus need
• - Apply to UM recommendations when
  phosphorus is used

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What to advise . . .

• On new lawns
• - Soil test to 6 depth
• - No test? Apply 2 lbs. P2O5/1,000 sq. ft.
• - Mix fertilizer well into top 6 of soil

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What to advise . . .

• All lawns
• - Sweep up, rake up, pick up
• - Soil test to establish baseline

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What to advise . . .

• Future? practices to increase infiltration

Rain garden in Maplewood, MN
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Information used
A Primer on Limnology. Bruce Monson. University
of Minnesota Water Resources Center. The Nature
of Phosphorus in Soils. Lowell Busman, et.al.
University of Minnesota Extension Service. Pub.
FO-6795 Phosphorus Transport and Availability in
Surface Waters. Gyles Randall, et.al. U of MN
Extension Service. Pub. FO-6796 Soil Test
Interpretation and Fertilizer Management for
Lawns, Turf, Gardens, and Landscape Plants. Carl
Rosen, et.al. University of Minnesota Extension
Service. Pub. BU-1731 Understanding Lake Data.
Byron Shaw, et.al. University of Wisconsin
Extension. Pub. G3582
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Ron Struss Water Resources EducatorUniversity of
Minnesota Extension Service 651-215-1950rstruss_at_u
mn.edu