An Entire HOUR on Phosphorus!

Beth Guertal

Department of Agronomy & Soils

Auburn University

The Plan

• Why we care about P in turfgrass.

• Why has P become an environmental concern?

• Where are rules about P fertilization being enacted?

• How does this affect P in turf?

Why you need P: • ADP and ATP – energy transformations in

plants.

• Essential part of DNA.

• Root development, especially lateral and

fibrous roots.

• Crop maturity – flowering, fruiting, seed

formation.

• Straw strength in cereal crops.

From D. Soldat, University of WI, creeping bentgrass

P deficiency

P deficiency - corn

Where Do You Need P? Phosphorus in the Soil

• total P in soil is low (~1/10th of N and 1/20th of

K)

• most of the native P is not available to plants –

insoluble

• over time, P added to soil (ex: fertilizer) is

fixed, and becomes unavailable to plants

• environmental influences, such as grass

species, soil type, rainfall, temperatures and

use of the area all determine nutrient needs

• there is both organic and inorganic soil P

Inorganic P in the Soil

• Two big groups: 1) Calcium phosphates,

and 2) Iron and Aluminum phosphates.

• The P that a turfgrass plant can use

(H2PO4

-) is a very small portion of the

total P.

• When fertilizer P is added, turfgrasses

have an uptake efficiency of around 10 to

40%, with the remaining fertilizer P fixed

into unavailable forms

Where Inorganic P is in the Soil…..

How that Affects P Fertilizer Recommendations….. P

erc

ent

of

maxim

um

yie

ld

VL Low Med High Very

High

Extremely

High

P in Soil

P Fertilizer Sources

• Triple super phosphate (TSP) – 0-44-0

• Diammonium phosphate

• Monoammonium phosphate

• Rock phosphate – not a soluble source of P

Why has P become an environmental concern?

How Does P Move?

• Does it leach?

• Does it move in water?

• How does it move in water?

• What does that all mean for how we manage P in our turfed landscapes?

What happens when your soil-test P gets too high?

Loss of P in Runoff……

0

100

200

300

400

500

600

700

800

0 365 730

P in

Le

ach

ate

(m

g)

days after first fertilization

Phosphorus in Leachate as Affected by P Rate – Sand Green

200 kg P2O5/ha

400 kg P2O5/ha

0

50

100

150

200

250

0 30 60 90 120 150 180 210 240 270 300 330 360 390 420 450 480 510

80S/10L/10P

80S/20L

90S/10L

90S/10P

days after construction

P in leachate

(ug/m

l)

What happens when your soil-test P gets too high?

Loss of P as leachate in very sandy soils…

0

5

10

15

20

25

30

0 20 40

75

150

225

300

0

5

10

15

20

25

30

0 10 20 30 40

3 months 6 months

Mehlich extractable P (mg kg-1)

depth

(cm

)

Soil-test P in sand-based putting greens, AU Club

Fertilizer Evaluation

Numbers for when things get bad…

• Water: One water-quality threshold level set by the USEPA is 0.3 mg L−1 of PO4

-3.

• Soil: For Mehlich 3: very low (VL): 0 to 12 lb A-1; low (L): 13 to 25 lb A-1; medium (M): 26 to 50 lb A-1, high (H): 51 to 100 lb A-1; very high (VH): 101 to 200 lb A-1, and, extremely high (EH): > 200 lb A-1.

(Soils with a CEC of 0 to 9)

How that Affects P Fertilizer Recommendations….. P

erc

ent

of

maxim

um

yie

ld

VL Low Med High Very

High

Extremely

High

P in Soil

Example P Soil-Test Recommendations…..

0

5

10

15

20

25

30

0 30 60 90

Meh

lich

Extr

acta

ble

So

il P

(m

g/k

g)

P rate (kg ha-1)

The effect of increasing rates of P fertilizer on extractable soil P

Where are rules about P fertilization being enacted?

Forms of P in Water – Boring, but it matters

• Soluble P – P dissolved in water, typically a filtered sample.

• Total P – P in water plus that attached to sediment (runoff not filtered).

• Orthophosphate – soluble P (may also be called dissolved or reactive P)

• Bioavailable P - dissolved and particulate P

• EPA water quality threshold is 0.1 mg L-1.

IL ME MD MI MN NJ NY VT VA WA WI

Effective dates:

2010 2008 2011-2013 2012 2004 2011, 2013 2012 2012 2013 2013 2010

Applicators affected:

“Applicator

for hire”

(licensed

commercial

, certified

applicators, and others)

All persons

Everyone All persons

All persons All persons All persons

All persons

All persons All persons All persons

Exempt

applicators

and allowed

Phosphorus

fertilizer use:

Golf

courses;

Commerci

al and Sod

farms;

Agricultura

l lands and

production

; Right-of-

ways; P

deficiency;

Establish

new turf;

Lawn repair

Agricult

ure; P

deficie

ncy;

Establi

sh new

turf;

Sod

farms;

Turf

repair;

Gardening

Agricultura

l

purposes;

Commerci

al and

Sod

farms; P

deficiency;

Establish

new turf; Turf repair

Golf

courses;

Commer

cial farm

land; P

deficienc

y;

Establish new turf

Golf

courses;

Sod farms;

Agricultural

lands and

production;

P

deficiency;

Establish new turf

Golf

courses;

Commercial

Farms;

Phosphorus

deficiency;

Establish

new turf; Turf repair

Gardens;

Agricultur

al lands

and

productio

n; Sod

farms;

Phosphor

us

deficienc

y;

Establish new turf

Golf

courses;

Sod

farms;

Agricultur

al lands

and

productio

n;

Phosphor

us

deficiency

;

Establish new turf

Phosphoru

s

deficiency;

Establish

new turf;

Turf repair;

Agricultura

l use;

Gardening

; Golf

courses

management plan

Establish

new turf;

Turf

repair;

Phosphor

us

deficiency;

Gardens;

Sod

farms;

Agricultur

al land or production

Sod

farms;

Agricultur

al land

and

productio

n;

Phosphor

us

deficienc

y;

Establish new turf

IL ME MD MI MN NJ NY VT VA WA WI Setbacks from water (buffer):

3 ft to 15 ft setback

None 10 ft to 15 ft setback

3 ft to 15 ft setback

None 10 ft to 15ft setback

3 ft to 20 ft setback

25 ft setback

None None None

Application on

frozen and saturated soils:

Prohibited No

restrictions

Prohibited

from Nov.

16 to Feb.

29 or on

frozen ground

Prohibited

No restrictions

Prohibited

during

heavy rain

or when

predicted,

on saturated

or frozen

ground, or

from Nov. 16

- Feb. 29

(Dec. 2 -

Feb. 29 for

professionals)

Prohibited

between

Dec. 1 and Apr. 1

Prohibited

from Oct.

16 to Mar.

31 or on

frozen ground

Package

label

prohibits

certain uses

Prohibited

on frozen ground

Prohibited

on frozen ground

Restrictions on

Phosphorus

lawn fertilizer sales:

No restrictions

Post

signs

about

fertilizer

use at

point of sale

Must sell

low

Phosphoru

s fertilizer

for lawns

unless

organic

and sold to

professional

No

restrictions

No restrictions

Sale

prohibited to

consumers

unless for

deficiency,

new turf, or turf repair

Display

Phosphor

us

fertilizer

separately

; Post

educational signs

Display

Phosphor

us

fertilizer

separately

; Post

educational signs

Sale of

lawn

maintenanc

e fertilizer

prohibited;

Can sell

existing stock

Sale

prohibited

unless for

an allowed

use and

properly

labeled;

Can sell

existing stock

No

display

but may

post sign;

Must sell

only for

specific purposes

The 2012 Florida Statutes

Model Ordinance for Florida-Friendly Fertilizer

Use on Urban Landscapes

• A mechanism for protecting local surface and

groundwater quality.

• Located within the watershed of a water body

or water segment that is listed as impaired by

nutrients …shall adopt the Model Ordinance for

Florida-Friendly Fertilizer Use on Urban

Landscapes.

Some of the research that is out there…

Shapiro et al., 1974

• Study conducted on health of lakes in TCMA

• Street sweeping reduces P concentration in runoff

Time of Year Storm Drain TP Conc

Feb. to mid-June 0.587 mg/L

Mid-June to mid-Oct. 0.256 mg/L

Oct. after leaf fall 1.095 mg/L

Barten and Jahnke, 1997

• Concluded phosphorus runoff to surface water bodies was from applied P fertilizer

– Not from landscape vegetation

• Sampled from May to October

– 70-90% of annual runoff occurs from Dec-March

• Did not measure runoff water volumes

– Assumed 10% volume of runoff

– Assumed all lawns have same runoff volume

• Other research: mean annual runoff ~ 1.1%

Kussow, 2001

• Annual losses of P in runoff water was 0.26 lb/A

– 81% of P collected was in runoff when soil was frozen

(0.05 lb/A during growing season)

• Small but consistent release of P into urban surface water from vegetation regardless of whether fertilizer is applied

• Healthy turf reduces water runoff volume and particulate P bound to soil

One of six people to have won:

• Nobel Peace Prize

• Presidential Medal of Freedom

• Congressional Gold Medal

Phosphorus Runoff and Landscape use: Agriculture

Land Use Soluble P Particulate P

--------- lb. P/A/year --------

Fallow 0.10 33.2

Conven. Corn 0.27 13.5

No-till Corn 0.98 1.9

Hay 0.39 0.02

Sources: Sharpley and Menzel, 1987; Rehm, et al., 1997.

105 106 107 205 206 207 208 305 306 307 308 108

Control

+

Control

+

Control

+

No P

+

Control

-

No P

-

No P

-

1.0 P

-

1.0 P

-

1.0 P

-

3.0 P

-

3.0 P

-

N

24 ft

8 ft

108

1.0 P

-

Turf Plots: Home Lawn

2005

1. no fertilizer

2. no phosphorus (N and K)

3. complete (1 lb P2O5)

4. complete (3 lbs P2O5)

2006 - 2009

1. no fertilizer

2. no phosphorus (N and K)

3. complete (0.33 lb P2O5)

4. complete (1 lb P2O5)

Runoff Results

Soluble Phosphorus Runoff from Frozen Soil (2005)

0

100

200

300

400

500

600

700

1 2 3 4 5 6 17

Runoff Event

So

lub

le P

ho

sp

ho

rus

Ru

no

ff (

mg

)

Control No P 1.0 P 3.0 PB - B - B - A

B - B - B - A

B - B - B - A

B - B - B - A

AB-B-AB - A

P runoff: 5 yrs of data

• [TP] and [RP] in runoff, soil test P and tissue [P] increased linearly with increasing P fertilizer application rate

• 86% of P runoff when soil was frozen

• ~72% of runoff P was RP

• P runoff can be reduced without affecting turf quality by not applying P fertilizer when soil test P levels are high

• Properly fertilized turf can reduce P runoff

Runoff of P – Some Conclusions

• Bare soil/thin turf – prone for greater loss via P-sediment erosion.

• Greater P losses if irrigation/rainfall follows immediately after application.

• Majority of P in runoff occurred in snowmelt.

• Inclusion of buffer strips significantly reduces P in runoff.

Phosphorus – Environmental Concerns

» Eutrophication - The over-enrichment of surface

water with mineral or organic nutrients, resulting

in a proliferation of plant life, especially algae

» Reduces the dissolved oxygen content of water

» Can result in death of aquatic organisms (worst

case scenario)

Phosphorus – Environmental Concerns

Critical P concentrations – lakes, ponds, slow-moving streams

» Avg concentration as low as 0.025 ppm

» Higher tolerance in fast-moving water

» Other factors may come into play

Puyallup, WA, Sand Study P Data

Multiple pairwise comparisons using the Dunn's procedure / Two-tailed test:

Sample Freq. Sum of ranks

Mean of ranks P (mg/kg) Groups

Bray P |PCSCU 4 15.5 3.875 23.5 A

Bray P |NatureSafe 1X 4 31.0 7.750 27.3 A B

Bray P |NatureSafe 1.5X 4 31.5 7.875 28.0 A B

Bray P |SoundGro 1X 4 63.5 15.875 66.3 B

Bray P |SoundGro 1.5X 4 68.5 17.125 75.3 B

There was no significant difference between treatments for Total Sand P

Average Total Sand Plot P = 280 mg/kg

Control Samples: Total P = 294 mg/kg Bray P = 16 mg/kg

Bonferri corrected significance level = 0.005

How to Handle a Site with High Soil Test P

• Don’t fertilizer with P.

• Remove clippings to ‘mine’ P from the site.

• Don’t let the site get bare – P in runoff is our biggest environmental issue.

The Sum Up

• Legal decisions on P fertilization often based on emotion rather than science.

• Properly applied – P fertilizers pose limited environmental hazard.

• The keys?

– Use soil tests for P fertilizer recommendations.

– Keep turf healthy and full.

– Avoid application to impervious areas and bare soil – clean up P fertilizer from pavement.

Questions? Thank you!