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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

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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, slivings@arb.ca.gov, 916-327-0822Dale Shimp, dshimp@arb.ca.gov, 916 324-7156 Richard Bode, rbode@arb.ca.gov, 916 323-8413

Research Division Contacts:Lei Guo, lguo@arb.ca.gov, 916-322-8097Dongmin Luo, dluo@arb.ca.gov, 916-324-8496Mike FitzGibbon, mfitzgib@arb.ca.gov, 916-323-2389

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