Nitrate Leaching From Turf Fertilization- A

Summary of FDEP-Funded Research

Laurie E. Trenholm

Urban Turfgrass BMP Specialist

UF-IFAS

Master Gardener Turfgrass Field Day – May 31st

Contact Crystal in the Statewide MG office to register

UF West Florida

Research and

Education Center, Jay UF Plant Science

Research and

Education Unit, Citra

Ft. Lauderdale

Research and

Education Center

DEP Nutrient Leaching Study

2004-2011

DEP Research – Nutrient Leaching

• Part of a FDEP $4.5 million grant to study nutrient leaching in lawn grasses

• Statewide project

• Apply nitrogen and phosphorus to lawngrasses under a wide variety of circumstances

• Measure visual quality, physiological responses, and nitrate and phosphate concentration in leachate

Lysimeters buried in center of each plot

As nitrate percolates downward through the column, it

collects in reservoir filled with gravel. At bottom of lysimeter

is a portal for tubing that runs to collection device

aboveground. To collect leachate, a vacuum pump is attached

the the tubing and water evacuated from base. A sub-sample

is collected for analysis.

Research Projects

1. Nitrate Leaching from Newly Sodded Turf

2. Nitrate Leaching Due to N Rate

3. Nitrate Leaching Due to N Source

4. Nitrate Leaching in Winter Months

5. Phosphorus Leaching

6. Nitrate Leaching Due to Mowing Height

7. Nitrate Leaching Due to Clipping Management

Nitrate Leaching from Newly Sodded Turf

• Floratam and Empire were planted as sod and nitrogen treatments applied same day

• Half of the plots received 2nd nitrogen application 30 days after planting

• N applied as water soluble urea 2 irrigation regimes

Treatments

N Rate Frequency

1. 0.5 lb N DOP

2. 1.0 lb N DOP

3. 2.0 lb N DOP

4. 0.5 lb N DOP + 30 DAP

5. 1.0 lb N DOP + 30 DAP

6. 2.0 lb N DOP + 30 DAP

Nitrate-N Leached Over 60 Day Study Period

Total NO3-N Leached

(kg N ha-1)

Empire Floratam

Source of Variation

Yr 1 Yr 2 Yr 1 Yr 2

Nitrogen Treatment (NT)

NS NS ** NS

Irrigation (IR) NS NS NS NS

NT * IR NS NS NS NS

NO3-N Leached From Newly Sodded Floratam

0

2

4

6

8

10

12

14

16

18

20

5/4/

2006

5/11

/2006

5/18

/2006

5/25

/2006

6/1/

2006

6/8/

2006

6/15

/2006

6/22

/2006

F1 N 0.5

F1 N 1.0

F1 N 2.0

F2 N 0.5

F2 N 1.0

F2 N 2.0

Nit

rate

-N L

ea

ch

ed

(kg

ha

-1)

Nitrate Leaching From Newly Sodded Floratam

0

5

10

15

20

25

30

35

40

45

0.5 1 2

FT DOP

FT 30 DAP

NO

3-

N L

each

ed

(kg

ha

-1)

N Rate (lbs 1,000 ft-2)

Percent of Applied N Leached From Newly Sodded Floratam

0

10

20

30

40

50

60

0.5 1 2

DOP

30 DAP

NO

3-

N L

each

ed

(kg

ha

-1)

N Rate (lbs 1,000 ft-2)

NO3-N Leached From Empire

Nit

rate

-N L

ea

ch

ed

(kg

ha

-1)

05

0

2

4

6

8

10

12

14

08

Conclusions

• Important to note that these rates of leaching are MUCH higher than from established turf

• Do not fertilize newly planted sod for 30-60 days after planting

• No pre-plant fertilizer incorporation, even with biosolid products

• Without an established root system, more N likely to leach

• Turf quality and establishment time not compromised by lack of fertilization

Nitrate Leaching Due to N Rate

• 3-yr study 2005-2007

• Established Floratam and Empire

• N applied in 4 applications throughout the year at rates of 1, 4, 7, or 10 lbs N 1,000 ft-2

• N applied as water soluble urea

• 2 irrigation regimes (1” @ 1x wkly, 0.5” @ 2x wkly)

Source of Variation Cumulative NO3-N Leached Cumulative NO3-N Leached

kg ha-1 kg ha-1

2006 2007

NR ** ***

Grass *** ***

IR NS *

NR*Grass NS ***

NR*IR * ***

Grass*IR NS NS

NR*Grass*IR NS *

Nitrogen Rate Study - Nitrate-N Leaching from Floratam

0

1

2

3

4

5Y

r 1 F

C1

Yr1

FC

2

Yr2

FC

1

Yr2

FC

2

Yr2

FC

3

Yr2

FC

4

Yr3

FC

1

Yr3

FC

2

Yr3

FC

3

Yr4

FC

4

1 lb N

4 lb N

7 lb N

10 lb N

Nitrogen applied as 100% soluble urea

NO

3-

N L

each

ed

(kg

ha

-1)

Trenholm et al. 2009

Nitrogen Rate Study -Percent of Applied N Leached from Floratam

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10

Yr 1 F

C1

Yr1 F

C2

Yr2 F

C1

Yr2 F

C2

Yr2 F

C3

Yr2 F

C4

Yr3 F

C1

Yr3 F

C2

Yr3 F

C3

Yr3 F

C4

SA 1 lb N

SA 4 lb N

SA 7 lb N

SA 10 lb N

Nitrogen applied as 100% soluble urea

Perc

en

t o

f A

pp

lied

N L

each

ed

Trenholm et al. 2009

Nitrogen Rate Study- Nitrate-N Leaching from Empire

0

10

20

30

40

50

Yr 1 F

C1

Yr2 F

C1

Yr2 F

C3

Yr3 F

C1

Yr3 F

C3

1 lb N

4 lb N

7 lb N

10 lb N

Nitrogen applied as 100% soluble urea

NO

3-

N L

each

ed

(kg

ha

-1)

Trenholm et al. 2009

Nitrogen Rate Study - Percent of Applied N Leached from Empire

0

5

10

15

20

25

30

35

40

Yr 1 F

C1

Yr1 F

C2

Yr2 F

C1

Yr2 F

C2

Yr2 F

C3

Yr2 F

C4

Yr3 F

C1

Yr3 F

C2

Yr3 F

C3

Yr3 F

C4

Zoy 1 lb N

Zoy 4 lb N

Zoy 7 lb N

Zoy 10 lb N

Nitrogen applied as 100% soluble urea

NO

3-

N L

each

ed

(kg

ha

-1)

Trenholm et al. 2009

Conclusions

• A healthy turf cover mitigated N leaching loads

• Importance of BMPs in maintaining a healthy turf cover (fertilization, mowing, irrigation)

• As SA matured after first year, nitrate leaching was minimized, regardless of N rate

• When turf cover was eroded, N leaching losses increased

• Current N recommendations for SA are good

Conclusions

• Zoysia more prone to increased leaching as applied N increased – Greater disease at higher N rates

• Zoysia N recommendations being revised downwards to reduce disease and potential for greater N losses

• Empire needs for N lower than in SA – quality and color good with less N

• Highest tendency for increased leaching occurred in spring and fall, not in summer

Nitrate Leaching Due to Nitrogen Source

• 8 nitrogen sources applied @ 1 lb N 1,000 ft-2 4x yr

• Established Floratam and Empire

• 4 yr study

Nitrogen Sources

N Sources –applied at 1 lb N every 60 days 1. Control

2. Water soluble ammonium nitrate

3. Water soluble urea

4. 30% Sulfur coated urea

5. 50% Sulfur coated urea

6. Polymer sulfur coated urea (Duration)

7. Polymer sulfur coated urea applied at 2 lbs N every 120 days

8. Milorganite

24

NO3-N Leaching Due to Nitrogen Source

Source of

Variation

2008 2009 2010 2011

Grass NS NS NS NS

Nitrogen

Source (NS)

*** NS NS *

G * NS *** NS NS NS

NO3-N Loads 2008

26

NO

3-N

Le

ach

ing

Load

K

g h

a-1

NO3-N Loads 2009-2011

0

5

10

15

20

25

2009

2010

2011

*

*

*

27

NO

3-N

Le

ach

ing

Load

K

g h

a-1

NO3-N Loading By Fertilizer Cycle, 2011

0

1

2

3

4

5

6

7

8

9

10

Winter FC1 FC2 FC3 FC4

NO

3-N

Lo

ad

ing

K

g h

a-1

Control

AN

Urea

30%SCU

50%SCU

PSCU

PSCU2lb

Mil

28

Conclusions • No significant differences in NO3-N loading between grasses

• Differences due to N source in 2 of 4 yrs

• Where differences occurred, greatest loading from AN (2008) and AN, PSCU at 2 lb twice a year, and Milorganite (2011)

• What about ordinances banning use of water soluble N sources?

• Should DACS allow Fertilizer Label Rule to change to allow application of 2 lb PSCU products?

• Should DACS allow Fertilizer Label Rule to change to allow application of up to 1 lb water soluble N?

Nitrate Leaching in Winter Months

• Apply N at different rates monthly throughout winter to Floratam and Ultimate zoysiagrass

• Control, .125, .25, .50, 1.0 and 2.0 lbs N 1,000 ft-2 mo.

• N applied as water soluble urea

Nitrate Leaching in Winter Months

Cumulative NO3-N Leached

2006-07 2007-08 2008-09

Nitrogen Rate ** * *

Grass *** *** ***

NR x Grass ** NS **

Nitrate Leaching in Winter Months (Yr 1 Nov-March Cumulative)

N Rate, lbs. 1,000 ft-2

2006-07

Nit

rate

-N L

eac

he

d (

kg h

a-1

)

Nitrate Leaching in Winter Months Yr 2 (Dec-Mar Cumulative)

N Rate, lbs. 1,000 ft-2

2007-08

Nit

rate

-N L

eac

he

d (

kg h

a-1

)

Nitrate Leaching in Winter Months Yr 3 (Nov-March Cumulative)

N Rate, lbs. 1,000 ft-2

2008-09

Nit

rate

-N L

eac

he

d (

kg h

a-1

)

Analysis of Variance by Month

ANOVA by

Month

Yr 1 Yr 2 Yr 3

Grass (G) ** * *

Nitrogen (N) *** *** ***

Month (M) *** *** ***

G*N ** NS **

G*M *** NS **

N*M *** *** ***

G*N*M *** NS **

35

NO3-N Loading By N Rate and Month Yr 2

36

Conclusions

• While there were few differences in leaching at the lower N rates, these loading rates exceed what occurs during the growing season

• Leaching higher in zoysia and at two highest N rates

• Turf quality/color not improved by fertilization

• Trend towards greater leaching in winter/spring than in fall months

• If additional N applications to be done due to summer bans or contractual obligations, they should be done in fall rather than spring

UF-IFAS Recommended Annual N Rates

*Empire zoysiagrass needs lower N rates than our official recommendations to reduce disease and nutrient loading – these are not “official IFAS recommendations” yet

North Central South

lbs. N 1000 ft-2

St.

Augustinegrass

2-4 2-5 4-6

Zoysiagrass 2-4 2-5 4-6

Empire* 2-3 3 3-4

Bahiagrass 2-3 2-4 2-4

Are all turf fertilization events

potential pollution events?

Other Factors to Reduce Nutrient Movement

• Do not apply nitrogen fertilizer at excessive rates – stick to the UF-IFAS recommendations

• Remove fertilizer granules from impervious surfaces

• Remove leaf clippings from impervious surfaces

• Use deflector shields around water bodies

• Maintain a buffer zone around water bodies

• All of these will likely have more impact on reducing pollution than nitrogen source used

We thank the Florida Department of

Environmental Protection for funding

this research