2014 Southeast Hay Convention
Effect of Polymer-Coated Urea on
Bermudagrass Forage Production
Introduction
•  Without AN, users of N face
risky alternatives.
Effect of Polymer-Coated Urea on
-  NH3 volatilization loss
Bermudagrass Forage Production
Urea
Ammonium Nitrate
(AN)
Kathryn M. Payne
Dennis W. Hancock, PhD
Department of Crop and Soil Sciences
University of Georgia
Ammonia Volatilization Of Urea
Factors Increasing Volatilization
–  é Temperature
1.  Fertilizer
Application
–  é Humidity
–  é Wind
2.  Hydrolysis of
Urea
CO(NH2)2 + 2H2O è 2NH4+ CO32(urease enzyme)
CO32- + H2O è HCO3- + OH-
–  é Soil Moisture
–  é Soil pH
3.  NH3 gas
Volatilized
–  é Organic Matter / Thatch
NH4+ + OH- è NH3 (gas) + H2O
–  ê Rainfall/ Irrigation after application
Introduction
Environmentally Smart Nitrogen
•  Without AN, users of N face
risky alternatives.
•  N release through coating rather than breakdown
of coating
-  NH3 volatilization loss
•  Enhanced Efficiency (EE) N
products may reduce
volatilization loss
Ammonium Nitrate
(AN)
-  Urease inhibition
-  Encapsulate & release
Urea
•  Release manipulated through polymer chemistry
and thickness
NBPT
•  Moisture is required; soil temperature is primary
regulator
Polymer
Coating
N N
N
+ H2 O
Katie Payne,
Graduate Research Assistant
1
N
N
N N
N
N
2014 Southeast Hay Convention
Effect of Polymer-Coated Urea on
Bermudagrass Forage Production
Goal and Objectives
Introduction
•  Without AN, users of N face
risky alternatives.
To evaluate the potential of ESN:Urea Blends
(0%, 50%, 75%, 100% ESN) in two split
applications relative to AN or Urea split into
four equal applications.
-  NH3 volatilization loss
Urea
Ammonium Nitrate
(AN)
•  Enhanced Efficiency (EE) N
products may reduce
volatilization loss
NBPT
-  Urease inhibition
-  Encapsulate & release
-  NBPT and ESN treated urea have
reduced volatilization by 64 and
81%, respectively. (Connell et al.,
2011)
-  ESN releases N too slowly and
reduces yield compared to NBPT
treated urea and conventional AN.
Compare these ESN blends and conventional
systems in terms of:
Polymer
Coating
2.  Forage yield distribution within the growing season
3.  Ammonia volatilization loss
4.  Recovery of the total N fertilizer applied to the crop
Treatments Compared
Application Rate at:
Green After After After After
Apps up
H1
H2
H3
H4
Total
Rate
Application Rate at:
Green After After After After
Apps up
H1
H2
H3
H4
N Source
--------------------- (lb of actual N acre-1) ---------------------
AN
Urea
0% ESN
50% ESN
75% ESN
100% ESN
Check
Treatments Compared
4
4
0
0
300
300
Application Rate at:
Green After After After After
Apps up
H1
H2
H3
H4
4
4
2
75
75
150
75
75
0
75
75
150
75
75
0
Katie Payne,
Graduate Research Assistant
75
75
75
75
75
75
75
75
Application Rate at:
Green After After After After
Apps up
H1
H2
H3
H4
Total
Rate
Treatments Compared
Total
Rate
N Source
--------------------- (lb of actual N acre-1) ---------------------
AN
Urea
0% ESN
50% ESN
75% ESN
100% ESN
Check
Total
Rate
--------------------- (lb of actual N acre-1) ---------------------
AN
Urea
0% ESN
50% ESN
75% ESN
100% ESN
Check
N Source
Urea
1.  Total forage production per year
Treatments Compared
N Source
Ammonium Nitrate
0
0
0
--------------------- (lb of actual N acre-1) ---------------------
AN
Urea
0% ESN
50% ESN
75% ESN
100% ESN
Check
300
300
300
2
4
4
2
2
2
2
0
75
75
150
150
150
150
0
75
75
0
0
0
0
0
75
75
150
150
150
150
0
75
75
0
0
0
0
0
0
0
0
0
0
0
0
300
300
300
300
300
300
0
2014 Southeast Hay Convention
Effect of Polymer-Coated Urea on
Bermudagrass Forage Production
Materials and Methods
Materials and Methods
•  Sites: Two UGA Ag. Exp. Stations
•  Analyzed for nutritive quality at
FEW lab *
-  Calhoun
-  Eatonton
•  Analyzed for nitrate conc. *
•  ‘Russell’ bermudagrass, 4
harvests
-  Colorimetric determination by nitration
of salicylic acid (Cataldo et al., 1975).
-  Reported as (NO3-N) ion mg kg-1 in DM
-  2010-12
-  New locations each year
•  Experiment Design: RCB
•  N Recovery Calculation
-  4 replications
-  Data analyzed by Proc Mixed in SAS
N Removed (fertilized
plot)
– N Removed (control
plot)
N Application Rate
•  Plots harvested with a forage plot
harvester to a height of 2.5 in
* Data not shown
-  Samples dried, ground (1 mm)
Materials and Methods
Results and Discussion
•  Ammonia Volatilization Traps
-  100 mL 0.1 M H2SO4 acid traps
-  Covered by pvc pipe enclosure for 7
days in the field
•  Analyzed for ammonium conc.
-  Extract colorimetrically analyzed for
NH4 (Mulvaney, 1996)
-  Reported as NH4-N conc. (mg L-1)
Weather Data
•  2011
-  Calhoun: drought
throughout growing
season
-  Eatonton: heavy rain in
mid-season
•  2012
-  Average rainfall at both
locations
200
Objectives
Calhoun
2010
2011
2012
60 Yr Avg
Compare these ESN blends and conventional
systems in terms of:
150
100
1.  Total forage production per year
50
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
3.  Ammonia volatilization loss
Month
250
Ammonium Nitrate
2.  Forage yield distribution within the growing season
0
Total Rainfall (mm)
•  2010
-  Rainfall below average at
both locations
Total Rainfall (mm)
250
Eatonton
4.  Recovery of the total N fertilizer applied to the crop
2010
2011
2012
90 Yr Avg
200
Urea
150
100
50
0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Month
Katie Payne,
Graduate Research Assistant
3
2014 Southeast Hay Convention
Effect of Polymer-Coated Urea on
Bermudagrass Forage Production
Forage Yield (lb acre-1 yr-1)
N Treatment Effects on Total
Forage Production Per Year
Objectives
Compare these ESN blends and conventional
systems in terms of:
14000
a 11500
a 1.  Total forage production per year
ab b b b Ammonium Nitrate
2.  Forage yield distribution within the growing season
3.  Ammonia volatilization loss
9000
4.  Recovery of the total N fertilizer applied to the crop
Urea
6500
c 4000
AN, 4 apps
Urea, 4
apps
0% ESN: 50% ESN: 75% ESN: 100% ESN:
100% Urea 50% Urea 25% Urea 0% Urea
Columns followed by same letters are similar at P = 0.05
No N
Control
Treatment
Forage Yield by Harvest –
Eatonton 2010
2000
d e H1
d H2
d H3
H4
Harvest
a 4.  Recovery of the total N fertilizer applied to the crop
Urea
Columns followed by same letters are similar at P = 0.05
Ammonia Volatilization Loss Following Mid-Season Fertilization
Objectives
60
Compare these ESN blends and conventional
systems in terms of:
a
(mg L-1)
NH4-N Conc.
50
1.  Total forage production per year
ab
40
Ammonium Nitrate
2.  Forage yield distribution within the growing season
3.  Ammonia volatilized after H2 fertilizer application
30
20
Ammonium Nitrate
2.  Forage yield distribution within the growing season
3.  Ammonia volatilization loss
a 0
a a a a b 1.  Total forage production per year
Treatment
a abc bc bc c a c ab ab bc ab c N SN N SN
a S E ES E ck
N e E
A Ur 0% 50% 5% 00% he
7 1
C
a b bc cd bcd Compare these ESN blends and conventional
systems in terms of:
(lb acre-1 yr-1)
4000
Objectives
Forage Yield
6000
4.  Recovery of the total N fertilizer applied to the crop
bc
c
10
Urea
c
c
0
Urea, 4
Apps
0% ESN: 50% ESN: 75% ESN: 100% ESN:
100% Urea 50% Urea 25% Urea 0% Urea
No N
Control
Treatment
Columns followed by same letters are similar at P = 0.05
Katie Payne,
Graduate Research Assistant
4
2014 Southeast Hay Convention
Effect of Polymer-Coated Urea on
Bermudagrass Forage Production
N Recovery
(lb N removed lb N applied-1)
Effect of Treatment on the
Recovery of Applied N
0.500
0.450
0.400
0.350
0.300
0.250
0.200
0.150
0.100
0.050
-
a ab abc Conclusions
• Total yield of the 50 and 75% ESN blends were
similar to that of AN.
abc bc c • Throughout the growing season, 50 and 75%
ESN blends achieved slow release of N without
erratic forage distribution.
• ESN blends reduced the amount of ammonia
volatilization/trapped.
AN, 4 apps
Urea, 4
apps
0% ESN:
50% ESN:
100% Urea 50% Urea
75% ESN: 100% ESN:
25% Urea 0% Urea
Treatment
Columns followed by same letters are similar at P = 0.05
Conclusions
Implications
•  Two equal split applications of a 50%:50% or
• ESN blend applications split twice per season
recovered similar amounts of applied N as
conventional AN, applied four times.
75%:25% blend of ESN:Urea could provide an
alternative to conventional AN recommendations.
–  Economic analyses should be conducted to assess the
• The nutritive value of the ESN blends were
generally similar to AN (data not shown).
cost-effectiveness of this promising alternative.
-  Nitrate levels in ESN blends of 50 and 75%
were lower than AN (data not shown).
•  Use of such blends reduces NH3 volatilization loss and
increases the recovery of applied N, reducing potential
environmental threats.
Basic Cost Analysis
Trt. QUESTIONS?
net
lb lb as $ as lb as $ as
Yield Forage Forage
trips $ trips Total N urea urea ESN ESN (lb/A/yr) Cost Value revenue 100 Urea x
300 300 4 100 Urea x
300 300 2 50 Urea:
300 150 50 ESN 25 Urea:
300 225 75 ESN 100 ESN 300 0 $210 0 $- 4 $20 $530 9461 0.0560 $1,324.50 $794.50
$210 0 $- 2 $10 $520 9483 0.0548 $1,327.63 $807.63
$105 150 $115.50 2 $10 $530.50 10426 0.0509 $1,459.63 $929.13
$157 75 $57.75 2 $10 $525.25 10035 0.0523 $1,404.88 $879.63
$- 300 $231 2 $10 9606 0.0563 $1,344.88 $803.88
$541 Values Determined Assuming
Urea Price: $0.70/ lb N
ESN Price: $0.77/ lb N
Forage Cost: Total Cost / Yield
50 lb DM @ $7/bale: $0.14/ lb DM
1 trip across the field: $5
Forage Value: Yield x $0.14/lb DM
Total Cost: $300 + fert $ + trip $
Net Revenue: Forage Value – Total Cost
Katie Payne,
Graduate Research Assistant
5
2014 Southeast Hay Convention
Effect of Polymer-Coated Urea on
Bermudagrass Forage Production
Mean TDN Concentration Across
All Years, Locations, And Harvests
Total Digestible Nutrients
Relative Forage QualitY
Mean RFQ Across All Years,
Locations, And Harvests
94
a ab 90
ab a ab b 88
86
84
82
80
495
c AN, 4
apps
Urea, 4 0 ESN: 50 ESN: 75 ESN: 100 ESN: Check
apps 100 Urea 50 Urea 25 Urea 0 Urea
a bc 490
(g kg-1)
(unitless index)
92
500
bc 475
470
d 465
460
AN, 4 apps Urea, 4
apps
0 ESN:
100 ESN
a ab (mg kg-1)
bc Nitrate (NO3-N) Conc.
Crude Protein (g kg-1)
c 125
120
115
110
d 105
100
Urea
0%
ESN
50%
ESN
75%
ESN
100% Check
ESN
Treatment
Number of Obs. Instances
10
9
8
7
6
5
4
3
2
1
0
>2500
>4500
Urea, 4 0 ESN: 50 ESN: 75 ESN: 100 ESN: Check
apps 100 Urea 50 Urea 25 Urea 0 Urea
Treatment
Katie Payne,
Graduate Research Assistant
b 2000
c 1500
Check
6
bc c d 1000
e 500
AN, 4
apps
Urea, 4 0 ESN: 50 ESN: 75 ESN: 100 ESN: Check
apps 100 Urea 50 Urea 25 Urea 0 Urea
Treatment
Incidence Of Risky No3-N Conc.
Observed Over 24 Harvests
AN, 4
apps
100 ESN:
Urea
a 2500
0
AN
75 ESN:
25 Urea
Mean No3-N Conc. Across all
Years, Locations, And Harvests
3000
c 130
50 ESN:
50 Urea
Treatment
a 135
c 480
Effect of N Treatment on CP averaged
over all years, locations, and harvests
140
ab 485
Treatment
145
abc