Yasuhito SHIRATO (NARO, Japan)

Calculating changes in soil carbon in Japanese agricultural land by IPCC-tier 3 modeling approach: use of modified Rothamsted carbon model

GSOC17 ＠ Rome

Rothamsted Carbon model

• One of widely used soil C model

• Simple and good performance

• Not validated in Japan

Inputs: weather, soil, management

Outputs: SOCMonthly step

6 sites4 sites

Paddy soils 5 sites

Upland crop fields

Long-term experiments for model validation

15 sites across country under variety of weather, soil typeEach site has several plots with different management (NPK, manure, straw, etc.)

Paddy

Upland (Other soils)

Upland (Andosols)

Paddy soils

Validation and modification of the RothC: Japanese version

Andosols

Anaerobic conditionSlow decomposition

Stable humus with active AlSlow decomposition of “HUM” pool

Modified model Original RothC: successful Modified model

Country scale simulation by using 3 versionsNational Inventory Report (NIR)

Anjyo: NPK+FYMb0

102030405060

1975 1976 1977 1978 1979 1980 1981

SOC

(t C

ha-1)

Fujisaka: NPK+FYM020406080

1935 1955 1975 1995

SOC (

t ha

-1)

OriginalModifiedMeasured

05

10152025303540

1976 1981 1986 1991

SOC

(t ha

-1)

NPK observedNPK+straw observedNPK modified modelNPK+straw modified model

Toyama

Arable soils: ~500 million ha

(Shirato & Yokozawa, 2005)(Shirato & Taniyama, 2003)(Shirato et al., 2004)

1 paddy2 cropland3 orchard4 managed grassland5 unmanaged grassland6 forest lands7 wetlands8 settlements9 other lands

Country scale simulation unit: 100m × 100m grid

1st grid:40′ x 1°(≒80 x 80 km)

2nd grid:5′ x 7.5 ′(≒ 10 x 10 km)

3rd grid: 30″ x 45″ (≒ 1 x 1 km)

4th grid: 3″ x 4.5″ (≒ 0.1 x 0.1 km)total: ca. 38,000,000 grids

Soil mapLand use map (1976, 1987, 1991, 1997, 2006, 2020)

Takata et.al (unpublished)

SOC map on the agricultural lands in JapanSoil Carbon monitoring program on the agricultural

lands by MAFF (2008 – present)

every years since 2008 to 2012 3,500 monitoring points

Estimation procedure

Class-matchingsoil type land use climate type

Paddy fieldsUpland fieldsGrass land･････

High 23.3 kg m-2

Low 0 kg m-2

Created by Forestry and Forest Products Research Institute

SOC map on the forest in JapanNational Forest Soil Carbon Inventory by Forest Agency

every 10 years since 2006 2,500 permanent plots (4 km×10km grid)

Estimation procedure

Soil (0-30cm) Deadwood Litter

High 23.3 kg m-2

Low 0 kg m-2

Forest soil C mapArable soil C map

National SOC map, Japan

GSOC map specifications1 km grids, Depth 0-30 cm, Soil carbon [tons/hectare], ･･･

Evaluating total GWP at country scale

Increase C inputs

CH4 and N2O increase

SOC increaseRothC

RothC+N2O modelDNDC-Rice

• Evaluating total GHGs (GWP) considering “Trade- off” by using three different models

• Country scale evaluation with tier 3 method.

N2O emission = A exp[B*(ECO2/SCN+Fn)]

DecomposedCO2

C:N of organic matter

Chemical

fertilizer N

96 data from USA (4 sites), German (4 sites) and Canada (1 site); 14 data from Japan (2 sites); 4 data from China (1 site)

RothC

N2O: Combination of the RothC and empirical N2O model (Mu et al., 2009)

Decom-position

DOC

H2

OxidationMethanogenesisReduction

CO2

CH4O2

Photosynthesis, C allocation

Litter fall Transport

Fe3+, Mn4+

Fe2+, Mn2+

CH4

Transport

Diffusion

CO2

N & water uptake

NH4+

CO2

Nitrifi.Denitrifi.

NO3-

NH3, N2, N2O, NO O2

CH4: DNDC-Rice modelModified version of DNDC for paddy rice field

Fumoto et al., 2008

3 GHGs, total　 GWP

Relative magnitude of emissionCH ４＞ CO2 (fossil fuel)＞ N2O ≒ CO2 (Soil C)

(fossil fuel)

(soil C)

(tCO

2-eq

. /ye

ar)

Literature

Future projection

• +10% C input decrease CO2 but increase CH4 and N2O. Total GWP increase.

• Extending MSD decrease CH4, and its application in 50% paddy field can offset the above increase in GWP. Total GWP decrease.

• -10% N application decrease N2O. Total GWP decrease more.

• “Mitigation scenario 3” can decrease 5% of total GWP including fossil fuel derived CO2.

Scenario C input Paddy water management

N fertilizer Mitigation potential vs. BAU（ ktCO2-eq./yr： minus: mitigation）CO2 (Soil C)

CH4 N2O CO2 (Fossil fuel Total　

GWPBAU conventional conventional conventional 939 18052 3857 15699 38547

Mitigation1 +10% conventional conventional -903 +1637 +471 +1205

Mitigation2 +10% Extend MSD* conventional -903 -1316 +471 -1748

Mitigation3 +10% Extend MSD* -10% -903 -1316 +234 -1985

Average of 2014-2050（ per year）Average of two climate change scenarios

*Mid-season drainage

Summary

• The RothC-Japanese version was developed based on long-term field experiments

• Country-scale SOC calculating system (Tier 3) was developed by linking the RothC model and spatial datasets (e.g. soil map, land use, weather, agricultural activity)

• N2O and CH4 was calculated, too, at country-scale, for considering trade-off between soil C sequestration and other GHG emissions