WM869 Results: Nitrate-N
Leaching Losses from
Lawngrasses
Laurie Trenholm, Ph.D.
Urban Turfgrass Specialist
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.
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
Source of
Variation
Floratam
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
20
18
16
14
12
10
8
6
4
2
0
F1 N 0.5
F1 N 1.0
F1 N 2.0
F2 N 0.5
F2 N 1.0
6/
22
/2
00
6
6/
15
/2
00
6
6/
8/
20
06
6/
1/
20
06
5/
25
/2
00
6
5/
18
/2
00
6
F2 N 2.0
5/
11
/2
00
6
5/
4/
20
06
Nitrate-N Leached (kg ha-1)
NO3-N Leached From Newly Sodded
Floratam
Percent of Applied N Leached From
Newly Sodded Floratam
NO3- N Leached (kg ha-1)
60
50
40
DOP
30 DAP
30
20
10
0
0.5
1
N Rate (lbs 1,000 ft-2)
2
NO3-N Leached From Empire
14
Nitrate-N Leached (kg ha-1)
12
10
8
6
4
2
0
05
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
• Without an established root system, more N likely
to leach
• Turf quality and establishment time not
compromised by lack of fertilization
• Sod typically fertilized prior to harvest, some N is
likely imported and mobile due to harvest and
transplant
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
***
*
***
Grass*IR
NS
NS
NR*Grass*IR
NS
*
NR*IR
5
4
1 lb N
4 lb N
7 lb N
10 lb N
3
2
1
Yr4 FC4
Yr3 FC3
Yr3 FC2
Yr3 FC1
Yr2 FC4
Yr2 FC3
Yr2 FC2
Yr2 FC1
Yr1 FC2
0
Yr 1 FC1
NO3- N Leached (kg ha-1)
Nitrogen Rate Study - Nitrate-N
Leaching from Floratam
Nitrogen applied as 100% soluble urea
Trenholm et al. 2009
10
9
8
7
6
5
4
3
2
1
0
F
Yr C1
1
F
Yr C2
2
F
Yr C1
2
F
Yr C2
2
F
Yr C3
2
F
Yr C4
3
F
Yr C1
3
F
Yr C2
3
F
Yr C3
3
FC
4
SA 1 lb N
SA 4 lb N
SA 7 lb N
SA 10 lb N
1
Yr
Percent of Applied N Leached
Nitrogen Rate Study -Percent of Applied N
Leached from Floratam
Nitrogen applied as 100% soluble urea
Trenholm et al. 2009
14
15
NO3- N Leached (kg ha-1)
Nitrogen Rate Study- Nitrate-N
Leaching from Empire
50
40
1 lb N
4 lb N
7 lb N
10 lb N
30
20
10
0
1
r
Y
1
C
F
2
r
Y
1
C
F
2
r
Y
3
C
F
3
r
Y
1
C
F
3
r
Y
3
C
F
Nitrogen applied as 100% soluble urea
Trenholm et al. 2009
17
40
35
30
25
20
15
10
5
0
F
Yr C1
1
F
Yr C2
2
F
Yr C1
2
F
Yr C2
2
F
Yr C3
2
F
Yr C4
3
F
Yr C1
3
F
Yr C2
3
F
Yr C3
3
FC
4
Zoy 1 lb N
Zoy 4 lb N
Zoy 7 lb N
Zoy 10 lb N
1
Yr
NO3- N Leached (kg ha-1)
Nitrogen Rate Study - Percent of Applied
N Leached from Empire
Nitrogen applied as 100% soluble urea
Trenholm et al. 2009
Conclusions
• A healthy turf cover reduced N leaching loads, even
at higher than recommended application rates
• Importance of BMPs in maintaining a healthy turf
cover (fertilization, mowing, irrigation)
• Turf should be fertilized during the growing season
– many can’t do this due to local ordinances
• Highest tendency for increased leaching occurred in
spring and fall, not in summer
Conclusions
• Current N recommendations for SA are good
• Zoysia more prone to increased leaching as applied
N increased, but less N required than SA to
maintain healthy turf cover
– Greater disease at higher N rates
• Zoysia N recommendations may be revised
downwards to reduce disease and potential for
greater N losses
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
**
23
24
Nitrate-N Leached (kg ha-1)
Nitrate Leaching in Winter Months
(Yr 1 Nov-March Cumulative)
N Rate, lbs. 1,000 ft-2
2006-07
Nitrate-N Leached (kg ha-1)
Nitrate Leaching in Winter Months
Yr 2 (Dec-Mar Cumulative)
N Rate, lbs. 1,000 ft-2
2007-08
Nitrate-N Leached (kg ha-1)
Nitrate Leaching in Winter Months
Yr 3 (Nov-March Cumulative)
N Rate, lbs. 1,000 ft-2
2008-09
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
**
28
NO3-N Loading By N Rate
and Month Yr 2
29
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, these data suggest they should be
done in fall rather than spring
NO3-N Leaching Due to N Source
2008-2012
8 Treatments:
•
•
•
•
•
•
•
•
Control
Ammonium nitrate @ 1 lb N 1,000 ft-2 every 60 days
Urea @ 1 lb N 1,000 ft-2 every 60 days
30% sulfur coated urea @ 1 lb N 1,000 ft-2 every 60 days
50% sulfur coated urea @ 1 lb N 1,000 ft-2 every 60 days
32.8% polymer coated urea @ 1 lb N 1,000 ft-2 every 60 days
32.8 polymer coated urea @ 2 lb N 1,000 ft-2 every 120 days
Milorganite @ 1 lb N 1,000 ft-2 every 60 days
31
Nitrogen Source Leaching StudyAnnual Load from Floratam 2008
NO3- Leached (kg ha-1)
0.4
0.35
0.3
Control
AN
0.25
0.2
0.15
0.1
0.05
0
Urea
30% SRN
50% SRN
30% PCU
30% PCU 2 lbs/120
Mil
Nitrogen Source Leaching StudyAnnual Load from Floratam 2009
33
Nitrogen Source Leaching StudyAnnual Load from Floratam 2010
34
Nitrogen Source Leaching StudyAnnual Load from Floratam 2011
a
ab
b
ab
35
Conclusions
• No differences between N sources in Floratam at
the rates applied in 3 of 4 years
• Soluble vs. controlled release was not typically an
issue in leaching in this research
• Can we raise the Urban Turf Rule to allow a 2 lb
application of CRF?
Overall Message
• Maintenance of healthy turf important to reducing nitrate
leaching losses
– Commercial operators are BMP trained, which covers all cultural
aspects of lawn care
– Homeowners???
• A healthy turf can take up the recommended IFAS
application rates with minimal leaching loss
• N source not as important when turf healthy and fertilizer
applied correctly
• Fertilizer application timing should coincide with the
growing season
37
We thank the Florida Department of
Environmental Protection for funding
this research