N2O Emissions – Is there anything we can to do cap the well?
Rodney Venterea
US Dept. of Agriculture - ARS
Dept. of Soil, Water, Climate / University of Minnesota
Ryo Fujinuma
John Baker
Kurt Spokas
Michael Dolan
Jason Leonard
Carl Rosen
Charles Hyatt
Bijesh Maharjan
•NRI-USDA CSREES/NIFA Air Quality Program
•USDA-ARS GRACEnet Project
•USDA-ARS Post-doctoral Fellowship
•International Plant Nutrition Institute’s Foundation for Agronomic Research with
support from Agrotain Intl. and Agrium Inc.
•Minnesota Corn Growers Association
•John Deere & Company
•Kingenta Corporation
Is there anything we can to do cap the well?
1998 2000 2002 2004 2006 2008 2010 2012
Atm
os
ph
eri
c N
2O
( p
pt
)
312
314
316
318
320
322
324
Atmospheric N2O
NOAA/ESRL halocarbons in situ program ftp://ftp.cmdl.noaa.gov/hats/n2o/insituGCs/CATS/global/insitu_global_N2O.txt
Atmospheric N2O: + 0.25% per year
20% above pre-industrial levels
ANTHROPOGENIC SOURCES
Fertilizer application: 40%
Manure application & mgmt: 40%
Biomass burning : 7%
Industrial: 14% Davidson, 2009; Mosier et al.,1998
1960 1970 1980 1990 2000 2010
T
g N
fert
iliz
er
co
ns
um
ed
(ap
pro
x. %
of
cu
rren
t co
nsu
mp
tio
n)
0
5
10
15
20
25
30
35China, 34% of total
India, 15%
U.S., 11%
Pakistan, 3%
Indonesia, 2.8%
African Continent, 2.8%
Brazil, 2.5%
France, 2.1%
Canada, 1.8%
Bangladesh, 1.2%
87% of total increase since 1980 occurred in China and India
http://www.fertilizer.org/
China
U.S. India
World Fertilizer Use
1 kg N2O-N = CO2 from
50 gallons of gasoline
GWP = 300 times CO2
• 1 kg N2O-N ha-1 ≈ 0.5 Mg CO2 ha-1
•Potential C Sequestration (CCX):
Conversion of cropland to reduced tillage = 1 to 1.5 Mg CO2 ha-1
IPCC, 2007
GWP= Global Warming Potential
% of total anthropogenic GHG emissions
ODP = Ozone Depleting Potential
N2O
Ravishankara et al. Science. 2009
“By 2050, N2O emissions could
represent > 30% of peak CFC
emissions of 1987.”
30+ Years of Soil N2O Emissions Research
1. Developed measurement systems
2. Put constraints on emissions estimates
3. Identified major emissions controls, regulators, and key process
4. Developed emissions models
• Recent emphasis: Develop practical field methods to reduce emissions
• Few empirically-based guidelines for reducing N2O while maintaining crop yields
Objective
• Review our recent research as it relates to N2O mitigation efforts
-Management of synthetic Nitrogen fertilizer
-Challenges & recommendations for future study
X
X
X
Irrigated Site
-Corn
-Potato
Dryland/naturally drained site
-Corn
Dryland/
Tile-drained site
-Corn
Gas Flux Chambers
Pro:
• Plot-scale studies & treatment comparisons
• Inexpensive
Con:
• Limited spatial and temporal coverage
• Physical disturbance
Automated Chambers
5/1/06 6/1/06 7/1/06 8/1/06 9/1/06 10/1/065/1/05 6/1/05 7/1/05 8/1/05 9/1/05 10/1/05 11/1/05
0
100
200
300
400
500
AA
U
4/1/07 5/1/07 6/1/07 7/1/07 8/1/07 9/1/07 10/1/07
F P PF FP
N2O flux (µg N m-2 h-1)
2005, 2006, 2007 Growing Seasons
F = Fertilizer application date
P = Planting date
Trapezoidal
Integration
Flux versus Time
Data
Cumulative Emissions
mg N m-2 ug N m-2 h-1
(1 kg N ha-1 = 100 mg N m-2)
Asynchrony between N fertilizer application and crop N demand
Iowa State University Extension
Corn N Uptake
High potential for generating N losses:
Provide substrate for soil microbial population
Preplant
53%
Fall application
35%
~ 10%
Controlled Release Fertilizers (CRFs) for Reducing N2O Emissions
GOAL: Achieve more gradual N release over growing season:
1. Polymer–coated urea (PCU): Diffusion through porous coating
2. Nitrification (NI) inhibitors: Blended or co-applied with fertilizer
Meta-analysis of 35 studies (Akiyama et al., 2009)
• On average 35% to 38 % reduction in N2O emissions
• Wide variation in effectiveness.
• Yield benefits req’d to justify cost have been inconsistent.
Polymer-coated Urea (PCU) for Irrigated Potato Production
Source Timing Rate (kg N ha-1)
1. Conventional urea (47%N) 4 split applications 270
2. PCU-1 (44%N) Before planting 270
3. PCU-2 (42%N) Before planting 270
Potato N Uptake
North Dakota State University Extension
Urea/UAN
PCUs
Controlled Release Fertilizers for Irrigated Potato Production
Hyatt et al. 2010. SSSAJ.
Three-yr mean N2O emissions
Becker, MN
N2O
em
issio
ns
(m
g N
m-2
)
0
50
100
150
200
Tu
ber
yie
lds (
ton
ha
-1)
0
50
100
150
200
Conventional Urea
Polymer-coated Urea 1
Polymer-coated Urea 2
N2O emissions Tuber yields
a
ab
b
Source Timing Rate (kg N ha-1)
1. Conventional urea (47%N) 4 split applications 270
2. PCU-1 (44%N) Before planting 270
3. PCU-2 (42%N) Before planting 270
Venterea et al. 2011. JEQ (In press)
Source Timing Rate (kg N ha-1)
1. Conventional urea (47%N) 4 split applications 270
2. PCU-1 (44%N) Before planting 270
3. PCU-2 (42%N) Before planting 270
Controlled Release Fertilizers for Irrigated Potato Production
Soil and leaching data for individual yearsLoamy sand, Becker, MN
Resid
ual
So
il N
(m
g N
kg
-1)
0
10
20
30
40
50
60
So
il-w
ate
r n
itra
te (
mg
N L
-1)
0
10
20
30
40
50
60
Conventional Urea
Polymer-coated Urea 1
Polymer-coated Urea 2
Residual Soil N (year 1)
a a
b
a
ab
b
Nitrate in Soil-Water(Spring following year 2)
•Decreased N2O
•Increased NO3- leaching
Direct emissions
N2O
Managed
field boundary
Direct and Indirect N2O Emissions
Indirect emissions
N2O
NO NH3
NO3-
Challenges:
1. Logistical - measuring all forms of N loss in a single experiment
2. GHG budgeting - estimating fraction of indirect losses converted to N2O
Controlled Release Fertilizers for Dryland Corn Production
Source Timing Rate (kg N ha-1)
1. Conventional urea (47%N) Sidedress (V4-V6) 146
2. Urea + DCD + NBPT (47%N) Sidedress (V4-V6) 146
Urea
Urea + NI +UI
Treatments applied to both CT and NT treatments (in place for > 15 yr)
Controlled Release Fertilizers for Dryland Corn Production
Source Timing Rate (kg N ha-1)
1. Conventional urea (47%N) Sidedress (V4-V6) 146
2. Urea + DCD + NBPT (47%N) Sidedress (V4-V6) 146
Venterea et al. 2011. (In review)
Three-yr mean N2O emissions
Rosemount, MN
N2O
(kg
N h
a-1
)
0
20
40
60
80
100
120
Conventional Urea
Urea with Inhibitors
Conventional Tillage No Till
Waukegan silt loam
Treatments applied to both CT and NT treatments (in place for > 15 yr)
Controlled Release Fertilizers for Dryland Corn Production
Source Timing Rate (kg N ha-1)
1. Conventional urea (47%N) Sidedress (V4-V6) 146
2. Urea + DCD + NBPT (47%N) Sidedress (V4-V6) 146
Venterea et al. 2011. (In review)
Three-yr mean grain yieldsRosemount, MN
Gra
in Y
ield
(M
g h
a-1
)
0
2
4
6
8
10
12
14 Conventional Urea
Urea with Inhibitors
Conventional Tillage No Till
Waukegan silt loam
Treatments applied to both CT and NT treatments (in place for > 15 yr)
1. No guidelines for knowing when/where specific products will be effective.
2. Many different formulations available, but little systematic comparison.
3. Appears to have potential, but needs to be optimized to site conditions (soil,
climate, crop phenology).
-PCUs: Select correct release rate
-NIs: Can have short duration of effectiveness (half life decreases with temp)
-Alternatives may have longer duration are being (e.g. biochar)
Controlled Release Fertilizers
Survey of MN corn producers (MDA/ UMN/ NASS, 2010)
91.7%
4.2%
1.1%
1.0% 0.3% 1.7%
Use of additives and specialty formulations
Urea or liquid N alone
Agrotain
Nutrisphere
ESN
Super U
Other
Chart does not include nitrapyrin use
• 8.3% : CRFs other than nitrapyrin
• 9.5% : nitrapyrin (fall AA application)
AA + Urea = 91%
Fertilizer Source Effects: Conventional Sources
Tera
gra
ms o
f N
itro
gen
0
1
2
3
4
Anhydrous Ammonia
Urea Solutions (UAN)
NH4 & NO3
salts
Other
Economic Research Service (2011)
(data for 2008)35%
23%
29%
4%
10%
Nitrogen Fertilizer Use by Type in U.S.
AA + Urea = 58%
Only 1 site-year of data comparing N2O emissions with AA and Urea prior to 2005
(Thornton et al., 1996)
Continuous corn Corn after soybeans
Three-yr average growing season N2O emissions
Rosemount, MN
N2O
(m
g N
m-2
)
0
100
200
300Anhydrous ammonia
Urea
b
a
b
a
Venterea et al. 2010. SSSAJ.
Anhydrous Ammonia versus Urea: Dryland Corn
Source Timing Placement Rate (kg N ha-1)
1. Urea (47%N) Pre-plant Broadcast and incorporated 146
2. AA (82%N) Pre-plant Injected into subsurface band 146
Treatments applied to both Corn following Corn and Corn following Soybean
Irrigated corn
Two-yr average growing season N2O emissions
Becker, MN
N2O
(m
g N
m-2
)
0
25
50
75
100
Anhydrous ammonia
Urea
b
a
Fujinuma et al., 2011 (submitted.)
Anhydrous Ammonia versus Urea: Irrigated Corn
Source Timing Placement Rate (kg N ha-1)
1. Urea (47%N) Pre-plant/Sidedress Broadcast and incorporated 90 / 90
2. AA (82%N) Pre-plant/Sidedress Injected and banded 90 / 90
GHG Impact of Change in Practice
(some wild extrapolations)
Emissions Factor (EF) Assessment
Study EFAA: EFurea
Thornton et al. (1996) 1.94
Venterea et al. (2010) 2.60
Fujinuma et al. (2011) 1.53
Average 2.0
• Assume EF ratio applies to all non-AA sources
• Complete shift away from AA 25% reduction
in fertilizer-derived N2O emissions across the U.S.
• But it’s probably not that simple, more studies needed.
Anhydrous Ammonia versus Urea
Worldwide AA Use
U.S. 85%
Canada 13%
Mexico 1%
Rest of world 1% (IFA Statistics)
Anhydrous Ammonia versus Urea: Indirect N2O Emissions
Fujinuma et al., 2011 (submitted); Maharjan et al., 2011 (in preparation)
N2O emitted
Direct and Indirect N2O emissions
Becker, MN
N2O
or
NO
(m
g N
m-2
)
0
25
50
75
100
NO
3
- (k
g N
ha
-1)
0
25
50
75
100Anhydrous ammonia
Ureab
a
NO emitted NO3
- leached
a
a
b b
Direct emissions
decreased with AA
Indirect emissions
increased with Urea
Anhydrous Ammonia versus Urea: Indirect N2O Emissions
2006 IPCC Guidelines for National Greenhouse Gas Inventories. De Klein et al.
Fujinuma et al., 2011 (submitted); Maharjan et al., 2011 (in preparation)
Lower limit of 95% CI0.2% of NO
0.05% of NO3
-
Total Direct plus Indirect N2O emissions
Becker, MN
To
tal N
2O
(m
g N
m-2
)
0
50
100
150
200
250
Anhydrous ammonia
Urea
Upper limit of 95% CI5% of NO
2.5% of NO3
-
Anhydrous Ammonia versus Urea: Indirect N2O Emissions
2006 IPCC Guidelines for National Greenhouse Gas Inventories. De Klein et al.
Lower limit of 95% CI0.2% of NO
0.05% of NO3
-
Total Direct plus Indirect N2O emissions
Becker, MN
To
tal N
2O
(m
g N
m-2
)
0
50
100
150
200
250
Anhydrous ammonia
Urea
Upper limit of 95% CI5% of NO
2.5% of NO3
-
Fujinuma et al., 2011 (submitted); Maharjan et al., 2011 (in preparation)
Fertilizer Placement Effects
Conventional AA Injection
• Slow tractor speed with high fuel use
• 15-18 cm deep band
Conventional “Deep” Applicator
Shallow AA injection
• Faster speed
•10-12 cm deep band
• Improved soil closure
• Less fuel use
New “Shallow” Applicator
(very few studies)
Fertilizer Placement Effects
Effect of AA Injection Depth on N2O Emissions
Breitenbeck and Bremner, 1986
AA injection depth (cm)
0 5 10 15 20 25 30 35
N2O
em
itte
d i
n 1
56 d
ays
(k
g N
ha
-1)
0
1
2
3
4
5
112 kg N ha-1
225 kg N ha-1
Webster clay loam (no crop)
2009 2010
Effects of AA placement depth on N2O emissions
Becker, MN
N2O
(m
g N
m-2
)
0
50
100
150
200
Deep
Shallow
b
a
b
a
Fujinuma et al., 2011 (submitted.)
WHY ?
Repeating experiment in finer texture soil
Anhydrous Ammonia Placement Effects: Irrigated Corn
Source Timing Placement Rate (kg N ha-1)
1. AA Pre-plant/Sidedress 18 cm 90 / 90
2. AA Pre-plant/Sidedress 12 cm 90 / 90
Time (d)
0 10 20 30 40 50
N
2O
flu
x (
ng
N c
m-2
h-1
) o
r
So
il N
O2
- co
nc
en
tra
tio
n (
g g
-1)
0
50
100
150
200
250
300
350
N2O flux
Soil NO2
-
r2 = 0.74
Greater N2O Emissions with Anhydrous Ammonia
Venterea and Rolston, 2000. J. Geophys. Res.
Tomato field, Sac. County, CA
Elevated Soil Nitrite (NO2-)
So
il N
O2
- (g
N g
-1)
AA
Urea
5/21/07 6/4/07 6/18/07 7/2/07
N2O
flu
x (
g N
m-2
h-1
)
Corn field, Rosemount, MN
Elevated Soil Nitrite (NO2-)
Venterea et al. 2010. Soil Sci. Soc. Am. J.
Greater N2O Emissions with Anhydrous Ammonia
Soil Nitrite (NO2-)
N2O flux
Greater N2O Emissions with Anhydrous Ammonia
Aerobic conditions
Venterea and Rolston, 2002.
Soil Sci. 167.
Soil Gas Concentration (ppm or %)
0 5 10 15 20
Dep
th (
cm
)
0
2
4
6
8
10
N2O (ppm)
O2 (%)
Intact soil core data
Soil gas O2 concentration (%)
18.5 19.0 19.5 20.0 20.5
So
il d
ep
th (
cm
)
0
10
20
30
40
50
0 2 4 6 8 10
Soil gas N2O concentration (ppm)
23 June 2006, WFPS = 42 %
Corn field, Rosemount, MN
O2 N2O
Laboratory kinetics experiments: N2O production under aerobic conditions
NO2
- added (g N g
-1)
0 10 20 30 40 50
N2O
pro
du
cti
on
(
g N
g-1
h-1
)
0.00
0.01
0.02
0.03
0.04
Non-sterile
-irradiated (5 Mrad)
Venterea, 2007. Global Change Biol.
NO2- added to soil N2O production rate
Biotic
Abiotic
Prod. rate = Kp [NO2-]
NO2- added to soil N2O production rate
Venterea, 2007. Global Change Biol.
Measured Kp
0 2 4 6 8 10 12 14 16
Pre
dic
ted
Kp
0
2
4
6
8
10
12
14
16
R2 = 0.70
Kp = a + b 10
-pH + c C
t + d SOC
N2O Production rate = Kp [NO2-]
Rate coefficient correlated with:
• Acidity (10-pH)
• Total organic carbon (Ct)
• Soluble organic carbon (SOC)
Laboratory kinetics experiments: N2O production under aerobic conditions
Venterea, 2007. Global Change Biol.
1/T (Kelvin-1
)
0.0032 0.0033 0.0034 0.0035 0.0036
ln K
p
-10
-8
-6
-4
-2
CT soil
NT soil
Forest soil
Ea (kJ mol
-1)
5 % 21 %
66 5671 6085 78
Temperature Sensitivity
Laboratory kinetics experiments: N2O production under aerobic conditions
Venterea, 2007. Global Change Biol.
Headspace O2 concentration (%)
0 5 10 15 20
Rate
co
eff
icie
nt
(Kp)
Sensitivity to O2
NO2- added
Laboratory kinetics experiments: N2O production under aerobic conditions
N2O
Pro
duction R
ate
Laboratory kinetics experiments: N2O production under aerobic conditions
Venterea, 2007. Global Change Biol.
Headspace O2 concentration (%)
0 5 10 15 20
Rate
co
eff
icie
nt
(Kp)
Sensitivity to O2
NO2- added
NO3- added N
2O
Pro
duction R
ate
Concentrated Band
NH3/NH4+
NO2- NO3
- AOB
Free ammonia toxicity
NOB
NO2-
N2O
Chemical RXN
with SOM
N2O
Nitrifier
denitrification
Nitrite-driven N2O production
Venterea, 2007. Global Change Biol.
High O2 N2
Broadcast Banded
Effects of Urea placement on N2O emissions
Engel et al., 2010
N2O
(m
g N
m-2
)
0
100
200
300
400
100 kg N ha-1
200 kg N ha-1
Nitrite-driven N2O production
High NO2- Low NO2
-
Banding of Urea
Nitrite-driven N2O production
Banding as a beneficial fertilizer management practice
Conserves Nitrogen/ Increases NUE
-Slows nitrification and nitrate leaching
-Limits contact with soil microbes
-Increases root access to N
-Decreases distance from plant to N source
• With banding, it may be possible to have:
-Greater overall NUE
-And greater N2O emissions
• N2O emissions usually are < 5% of applied N.
• More study needed.
Malhi et al., 1985. 1991; Yadvinder-Singh et al., 1994
Robertson and Vitousek, 2009
Nitrite-driven N2O production
AA(banded)
N Losses (N2O, NO, NO
3
-)
Becker, MN
kg
N h
a-1
0
25
50
75
100
a
b
Urea(broadcast)
Is there an optimum banding intensity or thickness that maximizes NUE and
minimizes N2O emissions ?
Banding as a beneficial fertilizer management practice
Conserves Nitrogen/ Increases NUE
-Slows nitrification and nitrate leaching
-Limits contact with soil microbes
-Increases root access to N
-Decreases distance from plant to N source
Malhi et al., 1985. 1991; Yadvinder-Singh et al., 1994
Robertson and Vitousek, 2009
Modeling nitrite-driven N2O emissions
0 5 10 15 20
Bio
mas
s d
en
sit
y (
cells
g-1
)
105
106
107
Time (d)
0 5 10 15 20
0
50
100
150
200
0
1
2
3
4
NH
4
+,
NO
3- (:
g N
g-1
)
NO
2
- (:
g N
g-1
)
Nitrobacter
NitrosomonasNH
4
+NO
2
-
NO3
-
Time (d)
Biomass dynamics nitrite accumulation
Time
Bio
mass
AOB
NOB
0 5 10 15 20
Bio
mas
s d
en
sit
y (
cells
g-1
)
105
106
107
Time (d)
0 5 10 15 20
0
50
100
150
200
0
1
2
3
4
NH
4
+,
NO
3- (:
g N
g-1
)
NO
2
- (:
g N
g-1
)
Nitrobacter
NitrosomonasNH
4
+NO
2
-
NO3
-
Time (d)
Biomass dynamics nitrite accumulation
Venterea and Rolston, JEQ. 2000
jj
jinhjs
j
j
jdC
CKKB
dt
dB
,
max,
• Little to no information on toxicity kinetics in soil
• Soil property effects
• Critical / threshold concentrations
Soil nitrite concentration (ug N g-1
)
Lateral distance from row (cm)
0 10 20 30 40 50 60 70
Dep
th (
cm
)
0
10
20
30
40
50
20
40
60
80
100
Tillage Management Effects on N2O Emissions
Potential for N2O emissions to enhance (or offset) GHG benefits of reduced tillage
Properties affected by long-term tillage mgmt
Bulk density
Water content
Temperature
Inorganic N
Organic carbon
Dissolved organic carbon
Soil structure
Tillage Management Effects on N2O Emissions
Potential for N2O emissions to enhance (or offset) GHG benefits of reduced tillage
Properties affected by long-term tillage mgmt
Bulk density
Water content
Temperature
Inorganic N
Organic carbon
Dissolved organic carbon
Soil structure
NT > CT NT = CT CT > NT
Aulakh et al. 1984
MacKenzie et al. 1998
Ball et al., 1999
Yamulki and Jarvis 2002
Baggs et al., 2003
Koga et al. 2004
Venterea et al., 2005
Rochette et al., 2008
Grageda-Cabrera et al., 2011
Lemke et al. 1999
Robertson et al. 2000
Choudhary et al. 2002
Kaharabata et al. 2003
Liu et al., 2005
Rochette et al., 2008
Jacinthe and Dick, 1997
Kessavalou et al. 1998
Lemke et al. 1999
Kaharabata et al. 2003
Liu et al., 2005
Venterea et al., 2005
Ussiri et al., 2009
Halvorson et al., 2010
Omonode et al., 2011
NT Greater CT Greater Not different
Anhydrous ammonia
N2O
(m
g N
m-2
)
0
100
200
300
400
500
Conventional tillage (CT)
No tillage (NT)
b
a
CT > NT
Venterea et al. 2005. JEQ.
Tillage Management Effects on N2O Emissions
Anhydrous ammonia Surface broadcast urea
N2O
(m
g N
m-2
)
0
100
200
300
400
500
Conventional tillage (CT)
No tillage (NT)
b
a
b
a
CT > NT NT > CT
Tillage Management Effects on N2O Emissions
Venterea et al. 2005. JEQ.
Nitrification-driven N2O production
KP (h-1
)
0.0000 0.0002 0.0004 0.0006 0.0008 0.0010 0.0012 0.0014
Dep
th (
cm
)
0
5
10
15
20
25
NT
CT
Denitrification-driven N2O production
DEA (g N g-1
h-1
)
0.00 0.05 0.10 0.15 0.20 0.25 0.30
De
pth
(c
m)
0
5
10
15
20
25
30
CT
NT
Vertical Profiles of Potential N2O Production
Venterea and Stanenas. 2008. JEQ.
Bulk density (g cm-3
)
1.0 1.1 1.2 1.3 1.4 1.5
De
pth
(c
m)
0
5
10
15
20
25
30
CT, June 21
CT, July 10
CT, Aug 15
NT, June 21
NT, July 10
NT, Aug 15
Bulk Density Profiles
Volumetric water content (cm3 H2O cm
-3)
0.10 0.15 0.20 0.25 0.30
Dep
th (
cm
)
0
5
10
15
20
25
30
CT, June 21
CT, July 10
CT, Aug 15
NT, June 21
NT, July 10
NT, Aug 15
Water Content Profiles
Labile carbon profiles
Soluble organic C or Mineralizable C (g C g-1
)
0 5 10 15 20 25 30 35 40
Dep
th (
cm
)
0
5
10
15
20
25
30
CT, soluble C
CT, min-C
NT, soluble C
NT, min-C
Soil pH profiles
Soil pH (1:1 M KCl)
5.0 5.2 5.4 5.6 5.8 6.0
Dep
th (
cm
)
0
5
10
15
20
25
30
CT
NT
Vertical Profiles of Physical and Chemical Properties
Venterea and Stanenas. 2008. JEQ.
Diffusion model
Source Term Sink Term
Denitrification
Nitrification
SPdz
ONdD
dz
dp
][ 2
][
][
][
][
3
3max
3
3
CK
C
NOK
NOVP
C
mNO
m
NO
][
][
][
][
2
2max
2
2
CK
C
ONHK
ONHVS
C
m
ON
m
ON
Modeling Tillage-Fertilizer Interaction Effects
][ 2
NOKP p 0S
Venterea and Stanenas. 2008. JEQ.
NT:CT ratio of N2O flux
0.1 1 10
Dep
th (
cm
)
0
5
10
15
20
Nitrification
Denitrification
Depth
of fe
rtili
zer
applic
ation
Model predictions
Agrees with tillage-by-placement pattern
(12/18)
Mixed application or no information (5/18)
Disagrees with tillage-by-placement pattern
(1/18)
NT > CT NT = CT CT > NT
MacKenzie et al. 1998
Ball et al., 1999
Yamulki and Jarvis 2002
Baggs et al., 2003
Venterea et al., 2005
Grageda-Cabrera et al., 2011
Koga et al. 2004
Rochette et al., 2008
Aulakh et al. 1984
Lemke et al. 1999
Robertson et al. 2000
Choudhary et al. 2002
Kaharabata et al. 2003
Liu et al., 2005
Rochette et al., 2008
Jacinthe and Dick, 1997
Lemke et al. 1999
Liu et al., 2005
Venterea et al., 2005
Ussiri et al., 2009
Omonode et al., 2011
Kaharabata et al. 2003
Kessavalou et al. 1998
Halvorson et al., 2010
Tillage Management Effects on N2O Emissions
Fertilizer Rate Effects on N2O emissions
Fertilizer Rate (kg N ha-1
)
0 50 100 150 200 250 300
N2O
em
issio
ns (
kg
N h
a-1
)
0
1
2
3
4
5
6N2O response to N rate
Fertilizer Rate Effects on N2O emissions
Fertilizer Rate (kg N ha-1
)
0 50 100 150 200 250 300
N2O
em
issio
ns (
kg
N h
a-1
)
0
1
2
3
4
5
6N2O response to N rate
Decrease inputs ?
By how much ?
Emissions
Expressed
on area-basis
Fertilizer Rate Effects on N2O emissions
Fertilizer Rate (kg N ha-1
)
0 50 100 150 200 250 300
N2O
em
issio
ns (
g N
kg
-1 N
up
take
)
0
5
10
15
20
Emissions
expressed
on a yield-
scaled
basis
Van Groenigen et al. 2010
Yield-scaled emissions
Minimized at intermediate rate
Curve results from:
• Exponential N2O production curve vs. N rate
• Linear or MM yield curve versus N rate
Fertilizer Rate Effects on N2O emissions
Fertilizer Rate (kg N ha-1
)
0 50 100 150 200 250 300
N2O
em
issio
ns (
g N
kg
-1 N
up
take
)
0
5
10
15
20
Emissions
expressed
on a yield-
scaled
basis
Van Groenigen et al. 2010
Curve results from:
• Linear N2O production curve vs. N rate
• Linear or MM yield curve versus N rate
Nitrogen Use Efficiency and N2O emissions
Van Groenigen et al. 2010
N surplus (kg N ha-1
)
-150 -100 -50 0 50
N
Yie
ld-s
cale
d
N2O
em
issio
ns (
g N
2O
-N k
g-1
N y
ield
)
0
2
4
6
8
10
12
14
y = 10.20 + 1.57 exp(0.0294 x)from Van Groenigen et al. (2010)
N surplus = Fertilizer N inputs – above-ground crop N uptake
Another elegant idea: N2O emissions will be minimized when NUE is maximized
Meta-analysis results
N surplus (kg N ha-1
)
-150 -100 -50 0 50
N
Yie
ld-s
cale
d
N2O
em
iss
ion
s (
g N
2O
-N k
g-1
N y
ield
)
0
2
4
6
8
10
12
14
y = 10.20 + 1.57 exp(0.0294 x)from Van Groenigen et al. (2010)
y = 3.10 + 1.95 exp(0.0280 x)
r2 = 0.58
Nitrogen Use Efficiency and N2O emissions
Van Groenigen et al. 2010
N surplus = Fertilizer N inputs – above-ground crop N uptake
Another elegant idea: N2O emissions will be minimized when NUE is maximized
Meta-analysis results
Zero-N treatment with NT
Very dry years: low N uptake
Whole curve shifted down:
Sidedress N application
Time
N2O
co
ncen
trati
on
Suppression of concentration gradient,
decreasing flux with time
Time after chamber deployed
Ch
am
ber
N2O
co
ncen
trati
on
Underestimation of
pre-deployment flux
The “Chamber Effect”
Livingston et al. 2006. Soil Sci. Soc. Am. J.
Larger chamber
Longer deployment time
The “Chamber Effect”
Smaller chamber
Shorter deployment time
Less porous soil More porous soil
Linear model
Non-linear Model 1
Non-linear Model 2
% U
ndere
stim
ation
NDFE Model
Time (hr)
0.0 0.2 0.4 0.6 0.8 1.0
Ch
am
ber
N2O
(g
N m
-3)
0.00
0.02
0.04
0.06
0.08
= 0.50 m3 air m
-3 soil
= 0.25 m3 air m
-3 soil
Higher air-filled
Porosity (50%)
Lower air-filled
porosity (25%)
Venterea and Baker. 2008. Soil Sci. Soc. Am. J.
Underestimation of fluxes in more porous soil
Curves generated by numerical model
•Both soils have same pre-deployment flux
Artifacts can confound treatment effects:
•Tillage, organic amendments bulk density or water content
Venterea and Baker. 2008. Soil Sci. Soc. Am. J.
Underestimation of fluxes in more porous soil
Soil-gas N2O concentration ( g N cm
-3)
0.0 0.1 0.2 0.3 0.4
Dep
th (
cm
)
0
2
4
6
8
10
= 0.50
= 0.25t = 0
t = 0
Higher air-filled porosity:
•Greater Diffusivity
•Smaller initial gradient
Venterea and Baker. 2008. Soil Sci. Soc. Am. J.
Underestimation of fluxes in more porous soil
Soil-gas N2O concentration ( g N cm
-3)
0.0 0.1 0.2 0.3 0.4
Dep
th (
cm
)
0
2
4
6
8
10
= 0.50
= 0.25
t = 1 hr
t = 1 hrt = 0
t = 0
Higher air-filled porosity:
•Greater Diffusivity
•Smaller initial gradient
•More susceptible to deformation
•Greater storage capacity for gas to accumulate
Underestimation of fluxes in more porous soil
Linear HM
No
rmali
ze
d f
lux (
calc
ula
ted
/ a
ctu
al)
0.0
0.2
0.4
0.6
0.8
1.0= 0.50 m
3 air m
-3 soil
= 0.25 m3 air m
-3 soil
-33%
-16%
50% air-filled porosity
25% air-filled porosity
Venterea and Baker. 2008. Soil Sci. Soc. Am. J.
Artifacts can confound treatment effects:
•Tillage, organic amendments bulk density or water content
Linear HM NDFE
No
rmali
ze
d f
lux (
calc
ula
ted
/ a
ctu
al)
0.0
0.2
0.4
0.6
0.8
1.0= 0.50 m
3 air m
-3 soil
= 0.25 m3 air m
-3 soil
-33%
-16%
0%50% air-filled porosity
25% air-filled porosity
Underestimation of fluxes in more porous soil
•Gives multiple solutions
• Inefficient
• Not exact for non-uniform soil
Venterea and Baker. 2008. Soil Sci. Soc. Am. J.
Linear HM NDFE JEQ 2010
No
rmali
ze
d f
lux (
calc
ula
ted
/ a
ctu
al)
0.0
0.2
0.4
0.6
0.8
1.0= 0.50 m
3 air m
-3 soil
= 0.25 m3 air m
-3 soil
-33%
-16%
0% 0.3%50% air-filled porosity
25% air-filled porosity
Underestimation of fluxes in more porous soil
Venterea. 2010. JEQ.
•Gives multiple solutions
• Inefficient
• Not exact for non-uniform soil
•Requires bulk density, water
content data (sources of error)
Non-uniformity of Flux Measurement Methods
Venterea. 2010. JEQ.
Soil water content (cm3 H
2O cm
-3 soil)
0.10 0.15 0.20 0.25 0.30 0.35 0.40
Th
eo
reti
ca
l fl
ux
un
de
res
tim
ati
on
(%
)
0
10
20
30
40
50
60Venterea et al. 2009a
Jarecki et al. 2008
Bhandral et al. 2009
Hayakawa et al. 2009
Shrestha et al. 2009
Rochette et al. 2008
Hc T
d clay FC
cm h g cm-3
% scheme
12 1.0 1.20 22 Quad
10 2.0 1.26 20 HM
11 1.0 1.09 10 LR
40 0.46 0.56 18 LR
15 1.0 1.10 35 LR
24 0.4 1.10 77 Quad
1. More consensus in methods needed
2. Refinement necessary to improve absolute accuracy:
• More use of micro-meteorological methods
• Faster response/higher precision instruments (shorter deployment times)
Conclusions
1. More studies needed to better determine optimization fertilizer
management practices:
1. Depth of placement
2. Banding intensity
3. Source and timing
2. GPS-guided N application technology to better match rate and
placement with crop demand and yield potential
3. Emissions models that better account for differences due to (i) source,
(ii) placement, and (iii) interactions among multiple factors
Conclusions
Optimization of fertilizer management is only part of solution; range of
activities is required:
1. Edge of field denitrification barriers / bioreactors or controlled drainage
systems to reduce stream nitrate inputs:
-Do practices designed to stimulate denitrification increase net
N2O emissions ?
2. Cover cropping / companion cropping / more diverse rotations to
reduce N requirements and retain more N during non-growing season
3. Restoration of riparian vegetation
4. Improved animal mgmt to reduce excess N in manures
5. Improved manure mgmt….