USEPA Inventory for U.S. using IPCC Guidelines Review of the IPCC 1996 National Inventory Guidelines for N2O from Agricultural Soils USEPA Inventory for U.S. using IPCC Guidelines Using the DAYCENT Model to Estimate N2O Emissions

Review of IPCC 1996 National Inventory Guidelines for N2O from Agricultural Soils

Atmospheric N2 N2O biological fixation N2O N2O Volatilization NOx, NH3 fertilizer production Volatilization NOx, NH3 manure agricultural land cattle leaching soil organic matter crops people N2O litter sewage

Nitrification [HNO] [X] Denitrification REDUCED OXIDIZED Nitrification NO NO NO NH4+ [HNO] NH2OH NO2- NO3- [X] N2O Denitrification N2 N2O NO NO2- NO3-

Total N2O-N Emissions from Country (kg N2O-N Y-1) = N2ODIRECT + N2OANIMALS + N2OINDIRECT

N2ODIRECT = [(FSN+FAN+FBN+FCR)*0.0125)] + Hist. Cult. (5 kg N ha-1 y-1)

Emission Factors used in IPCC 1996 Estimates of Agricultural Soil N2O Direct Emission 0.0125 +/- 0.01 kg N2O-N/kg N input Histosol Cultivation 5 kg (2-15) N ha-1 y-1 Livestock Management System dependent Indirect G 0.01 (0.002-0.02) kg N2O-N/kg N Indirect L 0.025 (0.002- 0.1) kg N2O-N/kg N Indirect S 0.01 (0.002 - 0.1) kg N2O-N/kg sewage-N

Biological N-fixation Synthetic Fixed N Animal Manures Estimate of Global N2O Emissions Directly From Agricultural Fields in 1996 N input and N2O Production in Tg N NOX 12 NH3 Biological N-fixation Crop Residue N2O ~2.2 30 Corn Synthetic Fixed N Animal Manures Soy Bean 65 83 NO N2O Nitrification NH4+ NO2- NO3 Denitrification NO3 N2O N2

N2OANIMALS = N2O LIVESTOCK MANURE MANAGEMENT

Emission Factors used in IPCC 1996 Estimates of Agricultural Soil N2O Direct Emission 0.0125 +/- 0.01 kg N2O-N/kg N input Histosol Cultivation 5 kg (2-15) N ha-1 y-1 Livestock Management System dependent Indirect G 0.01 (0.002-0.02) kg N2O-N/kg N Indirect L 0.025 (0.002- 0.1) kg N2O-N/kg N Indirect S 0.01 (0.002 - 0.1) kg N2O-N/kg sewage-N

Estimates of Global N2O Emissions From Animal Production - 1996 N2O ~2 Tg NH3 ~22Tg NOX ~3Tg NO N2O Organic Waste ~120Tg N NH4+ NO2- NO3 Mineralization Nitrification NO3- N2O N2 Denitrification

N2OINDIRECT = N2O(G) + N2O(L) + N2O(S)

Emission Factors used in IPCC 1996 Estimates of Agricultural Soil N2O Direct Emission 0.0125 +/- 0.01 kg N2O-N/kg N input Histosol Cultivation 5 kg (2-15) N ha-1 y-1 Livestock Management System dependent Indirect G 0.01 (0.002-0.02) kg N2O-N/kg N Indirect L 0.025 (0.002- 0.1) kg N2O-N/kg N Indirect S 0.01 (0.002 - 0.1) kg N2O-N/kg sewage-N

N2O Indirect = N20(G) + N2O(L) + N2O(S) 1996 Estimate of Global N2O Emissions Indirectly Derived from AGN Input N2O Indirect = N20(G) + N2O(L) + N2O(S) NH3 NOX ~13 Tg N NH3 9Tg N N2O ~2.2 Tg N NO3 NO3 N2O N2

__________________________________________________________________ Relationship of type of crop to measured N2O emissions in temperate agricultural systems from 35 studies published since 1994. __________________________________________________________________ Crop N2O Emitted as % of N Applied Number of Studies (range) ______________________________________________________________________________ maize 0.5 - 7.3 9 spring barley or wheat 0.3 - 6.8 7 other crops 0.2 - 2.5 4 grasslands 0.2 - 12 11 fallow fields 0.1 - 1.0 4

Effect of fertilizer N source on N2O emissions in temperate agricultural systems ______________________________________________________________________________ N Source N2O Emissions Number of Studies % of fertilizer N applied Range Mean Anhydrous ammonia 7.3 1 Urea 0.2 - 3.8 1.6 13 Manure 1.0 - 3.2 2.2 4 Ammonium nitrate 1.2 - 3.6 2.6 5 Urea/ammonium nitrate 0.1 - 6.8 2.6 5 Calcium nitrate 5.2 - 12 7.7 4 Ammonium sulfate 0.2 - 1.0 0.5 3

Changes in Atmospheric N2O Concentration: Measured and Modeled (Mosier and Kroeze, 2000)

USEPA Inventory for U.S. N2O Emissions using IPCC Guidelines

USEPA, 2001 Inventory of U.S. Greenhouse Gas Emissions & Sinks

Process Models to Replace IPCC Factor-based National Inventories A few points that need to be considered: Anthropogenic N2O Emissions Indirect N2O Emissions Livestock Grazing Appropriate Data for Model Verification Model Intercomparison Uncertainty Analysis

Using the DAYCENT Model to Estimate N2O Emissions

DAYCENT APPLICATIONS DAYCENT was used to calculate net greenhouse gas flux (GHGnet) for different land management and climate scenarios. GHGnet = DSOC + CN2O + CNfert + CCH4 DSOC = Change in Soil Organic Carbon CN2O = CO2-C equivalents of N2O emissions CNfert = CO2-C emissions of N fert production CCH4 = CO2-C equivalents of CH4 uptake Initial condition = soil depleted of C due to > 50 years of conventional tillage winter wheat/fallow

DAYCENT MODEL VALIDATIONS Soil Organic C

N2O Emissions

CH4 Uptake

Short Term Simulations Using Sterling, CO Weather Reduction of the fallow period and conversion to no-till result in increased flows of CO2-C to SOC: DSOC

N2O emissions are similar N2O-C Equivalents GHGnet is reduced with annual cropping even though N fertilizer additions and grain yields are higher with annual cropping: GHGnet

Long Term Simulations Using CPER, CO Weather Conversion from winter wheat/fallow to high intensity agriculture results in sequestration of CO2-C in Soil Organic Carbon (SOC): DSOC

But irrigation and N fertilization also lead to higher N2O emissions: N2O-C Equivalents GHGnet is negative only during the first 25 year period following conversion: GHGnet