n2o emissions is there anything we can to do cap … uc...n 2 o emissions – is there anything we...

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


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


N2O emissions Tuber yields

a

ab

b





Venterea et al. 2011. JEQ (In press)





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



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


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)





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






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


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


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


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

-


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

-


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


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.


Soil Nitrite (NO2-)

N2O flux


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


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)



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



Headspace O2 concentration (%)

0 5 10 15 20

Rate

co

eff

icie

nt

(Kp)

Sensitivity to O2

NO2- added


N2O

Pro

duction R

ate



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


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


High NO2- Low NO2

-

Banding of Urea


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


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


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


Jacinthe and Dick, 1997

Kessavalou et al. 1998

Lemke et al. 1999


Liu 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.


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


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


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


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


Grageda-Cabrera et al., 2011

Koga et al. 2004


Aulakh et al. 1984

Lemke et al. 1999

Robertson et al. 2000

Choudhary et al. 2002


Liu et al., 2005


Jacinthe and Dick, 1997

Lemke et al. 1999

Liu et al., 2005


Ussiri et al., 2009

Omonode et al., 2011


Kessavalou et al. 1998

Halvorson et al., 2010


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



)

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



)

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



)

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


Curve results from:

• Linear N2O production curve vs. N rate

• Linear or MM yield curve versus N rate

Nitrogen Use Efficiency and N2O emissions


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


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



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



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


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



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



•Gives multiple solutions

• Inefficient

• Not exact for non-uniform soil


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



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….

n2o emissions is there anything we can to do cap … uc...n 2 o emissions – is there anything we...

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