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Research on N2O Emissions from Agricultural Soils
in California
California Air Resources BoardMay 21, 2008
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- Background
- Current California N2O inventory
- Critical research gaps
- Ongoing and proposed research efforts
State Agencies
Industry
- Discussion
Presentation Outline
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- Signed into law on September 27, 2006
- Mandating sweeping strategies to curb GHGs
- Early Action items
- 44 Early Action measures
- Measure 31: Collaborative Research to UnderstandHow to Reduce GHG Emissions From Nitrogen Land Application
- Scoping Plan
-Additional measures for GHG reductions
AB 32 Implementation
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-A Kyoto Greenhouse Gas (GHG)• The Kyoto six: CO2, CH4, N2O, HFCs, PFCs and SF6
-Global Warming Potential • 310 (IPCC, 2001); 298 (IPCC, 2007);
-Produced both naturally and artificially: • Natural processes: nitrification/denitrification, and combustion
• Artificial reaction: catalytic chemical oxidation (chemical manufacturing)
-Background concentration in the atmosphere: ~310 ppbv
• ~275 ppbv in 1750, ~290 ppbv in 1950, currently >310 ppbv
• Increase rate since 1950: 0.6 ppbv or 0.2% per year
• Largely caused by increased nitrogen fertilizer use
- Half-life (t1/2) in the atmosphere: 114 years
What is N2O?
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-Contributes ~ 3% to California’s overall inventory -Agricultural soil management is the largest source (>50%)
N2O Inventory
Industrial9.26% (1.4)
Residential0.40% (0.1)
Ag Soil Management
52.3% (8.1)
Electricity Generation2.61% (0.4)
Other Ag Related4.5% (0.7)
Transportation30.23% (4.7)
CO2
89.49% (488.9)
HGWP gases2.62% (14.3)N2O
2.85% (15.5)Other (ODS)0.28% (1.5)
CH4
4.76% (26.0)
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N2O From Agricultural Soils
Manure deposited on
pasture/range or spread
27%
Crop residues 2%
Synthetic fertilizers
60%N fixed by legume crops
11%
<1%
Organic fertilizers
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2004 Emissions from N Application
Synthetic fertilizers85%
Manure fertilizers15%
Commercial Organic fertilizers
<1%
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2004 Emissions from N Application
Synthetic fertilizers (direct)
64%
Synthetic fertilizers (indirect)
7%
Synthetic fertilizers (leaching & runoff)
14%
Manure/Dialy Spread2%
Manure (leaching & runoff)
6%
Nitrogen volatilized from manure
7%
Organic fertilizers (direct)
<1%Organic fertilizers
(indirect)<1%
Organic fertilizers (leaching & runoff)
<1%
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N2O Inventory Estimation Methods
-IPCC Tier 1 approach (Emission Factor = EF) • Current California method for estimating agricultural soil N2O emissions• N2O Emissions = Activity x EF = Soil N Inputs x EFs
-IPCC Tier 2 approach (disaggregated EFs)Considering site specific information
-IPCC Tier 3 approach: modeling/measurement
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N2O Emission and N Fertilizer Use
- Annual use trend (California Department of Foodand Agriculture, 2006)
● 1990-2001: Relatively stable between ~500,000 - 600,000 tons
● 2002-2004: >900,000 tons0
200,000
400,000
600,000
800,000
1,000,000
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
Year
N (
Sh
ort
to
ns)
0.00
2.00
4.00
6.00
8.00
10.00
1990 1992 1994 1996 1998 2000 2002 2004
Year
N2O
Em
issi
on
s (M
MT
CO
2E
) Ag Soils
Direct
Indirect
N Fertilizer Use Trend in CA
N2O Emissions from Agricultural Soil in CA- Total N2O emission from agricultural soilamounts to ~8.1 mmtCO2e in 2004
- N2O emissions were dominated by N fertilizer use (~60%)
- Direct emissions contribute about threetimes more N2O than indirect emissions
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Overview of N2O Research
- Nitrogen fertilizer management has been an important research topic
• Nitrogen fertilizer efficiency• Leaching/runoff controls
- Direct field observations on N2O emissions are limited in USA,especially for California
- Process models (DNDC, DAYCENT) predict trends, are lessreliable on events due to unknown localized parameters
- Major regulating factors on N2O emissions
• Inorganic N sources (practice dependent)• Soil water content (practice dependent)• O2 sources• Carbon sources• Temperature
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Summary of N2O Field Measurement Data
Observation of N2O Emission Rates from Field Experiments
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10
20
30
40
50
60
70
0 100 200 300 400 500 600 700 800
N input (Kg N ha-1 y-1)
N2O
em
issi
on
(K
g N
ha
-1y-1
)
CA Germany UKSpain Japan India
US China New ZealandAustralia
Y=0.01XCurrent CA default
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- Need crop-, practice-, and local-specific N2O emissiondata for California
� Baseline emissions inventory estimates
- Need to improve model applicability, validity, andreliability
� Monitoring data for model calibration/validation � Improved spatial and temporal resolution
Critical Research Gaps
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CDFA Sponsored N Fertilizer Related Research
California Department of Food and Agriculture- FREP (Fertilizer Research and Education Program)
• Established in 1990 • Funds fertilizer, education, and environmental research
• Funding level: Typically 3 years at $50,000/year
• Funded 139 projects to date• More than 55% of funded projects directly relate to N fertilizer use
- Past project focus• N fertilizer use under diversified cropping and irrigation systems and regions• Best Management Practices (BMPs)
• Other environmental concerns (air and water)
• Outreach/Education
- http://www.cdfa.ca.gov/is/fflders/frep.html
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Quantifying Carbon Dynamics and Greenhouse Gas Emissions in Agricultural Soils of California: A Scoping Study
C. Li, W. Salas, M. Los Huertos
Objectives• DNDC was used to estimate recent CO2 & N2O emissions at the county scale for CA
Results• CA agricultural soils are sequestering C and have the potential to reduce N2O
emissions• Large uncertainties due to uncertainties in initial soil conditions and crop residue
management.
Recommendations• Establish a program to collect data on residue and manure management.• Further validate the DNDC model, over a range of California
CEC-Sponsored N Fertilizer Related Research
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CEC-Sponsored N Fertilizer Related Research
Integrated Assessment of the Biophysical & Economic Potentialfor GHG Mitigation in CA Agricultural Soils
De Gryze, S., R. Catala, R.E. Howitt, and J. Six
Objectives• DayCent used to estimate GHG emissions and mitigation in CA agriculture under
alternative and conventional management• Evaluate financial incentives to stimulate adoption of alternative cropping practices
Results• Potential sequestration of 0.5 - 3.3 Mg CO2-eq ha-1 yr-1 by combining alternative
practices• Daily N2O fluxes were predicted fairly well. Variability of peak events inaccurate.
Recommendations• Multi-year and multi-field contracts to reduce possible discount in C credit prices for
agricultural mitigation• Create a dataset of N2O fluxes in CA agroecosystems• Improve N2O emission routines of existing models
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Jan-2004 Jul-2004 Jan-2005 Jul-2005 Jan-2006 Jul-2006
0
50
100
150
200
250
modeled N2O emissionsmeasured N2O emissions
Jan-2004 Jul-2004 Jan-2005 Jul-2005 Jan-2006 Jul-2006
N2O
emission
s (g N
ha-1
day
-1)
0
50
100
150
200
250
Standard tillage
Conservation tillage
22 May 2006
22 May 2006
Modeled and measured N2O emissions versus time for the standard and conservation tillage treatments at the Field 74 experiment (De Gryze et. al. 2008)
CEC-Sponsored N Fertilizer Related Research
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CEC PIER Request for Proposal
• Released March 17, 2008• Due date May 20, 2008• Projects will begin in November• Total of up to $2,900,000 for the six research topics• Research Topic 2: N2O Emissions from the Application of
Fertilizers in Agricultural Soils ($500,000; 3 yrs max)
• http://www.climatechange.ca.gov/research/funding.html
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Suggested Research Project
Title: Establish baseline N2O emissions from nitrogen fertilizer use based on California specific emission rates
Approach: Conduct field experiments to measure N2Oemission rates at multiple sites in key agriculturalcounties on major crops
Key considerations:�N fertilizer type (NO3
-, NH4+)
�Soil properties (organic matter content, texture) �Irrigation practice�Climate (temperature, precipitation)
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Discussion
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Staff Contacts
Planning and Technical Support Division Contacts: Shelby Livingston, [email protected], 916-327-0822Dale Shimp, [email protected], 916 324-7156 Richard Bode, [email protected], 916 323-8413
Research Division Contacts:Lei Guo, [email protected], 916-322-8097Dongmin Luo, [email protected], 916-324-8496Mike FitzGibbon, [email protected], 916-323-2389
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