GSP Webinar: RECSOIL: Recarbonization of Global Soils, 17 June 2020, Zoom platform. Presentation by Rattan Lal, Distinguished University Professor of Soil Science and Director of the Carbon Management and Sequestration Center, The Ohio State University, Ohio, USA.

1. 1
Carbon Management and
Sequestration Center
Status and Challenges of Global Soil Carbon Sequestration
Dr. Rattan Lal
Carbon Management and Sequestration Center
The Ohio State University
Columbus, OH 43210 USA
RECSOIL,17th June, FAO Rome,Italy

2. 2
Carbon Management and
Sequestration Center
COMPONENTS OF SOIL CARBON POOL
Soil Carbon Pool
Organic Inorganic
Pedogenic Lithogenic
Carbonates Bicarbonates
Live
- Fauna
- MBC
Undecomposed
(Detritus)
Decomposed
Protected Unprotected
DOC POC MOC

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Carbon Management and
Sequestration Center
3.0
2.0
1.5
1.0
0.5
0.3
0 1 2 3
Depth(m)
SOC Stock (103Pg)
0.677
0.993
1.505
1.778
2.060
3.000
0.612
Peatlands
DEPTH DISTRIBUTION OF GLOBAL SOIL ORGANIC CARBON STOCKS
Lal (2018)
Atmosphere = 820 Pg
Vegetation = 620 Pg
Need a Similar chart for SIC

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Carbon Management and
Sequestration Center
TECHNICAL POTENTIAL OF C SEQUESTRATION
I. Soils ……………………………. 1.45 – 3.44 Pg C/yr (2.45 Pg C/yr)
Lal (2018)
II. Terrestrial Biosphere by 2100
• Soils ……………………….. 178 Pg
• Vegetation ………………… 155 Pg
Total 333 Pg (157 ppm CO2)
Lal et al. (2018)

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Carbon Management and
Sequestration Center
PATHWAYS TO SOIL CARBON SEQUESTRATION
Pathways to Soil Carbon
Sequestration
Soil Organic Carbon Soil Inorganic Carbon
Standing
Biomass
Repository of
Organic Matter
Secondary
Carbonates
Leaching of
bicarbonates
Weathering of
silicate minerals
Natural
minerals
Cement

6. 6
Carbon Management and
Sequestration Center
CREATING POSITIVE C BUDGET
Soil Carbon Sequestration Soil Carbon Depletion
Losses
Biochar
Compost
Cover Crops
Root Biomass
Crop Residues
Erosion
Leaching
Decomposition
Residue
Compost
Root Biomass
Erosion
Leaching
Decomposition
Gains
Gains
Losses

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Carbon Management and
Sequestration Center
SOC MEASUREMENT
FOR TRADING CARBON CREDITS
Quantity: SOC stock (Mg C/ha)
Depth: 1-m or more
Frequency: 1-5 yr. depending on land use
Precision: Whole # in Mg/ha
Scale: Landscape or farm scale
With the first measurement of SOC in 1850,
there have been numerous advances since 2000
(i.e., LIBS, INS)

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Carbon Management and
Sequestration Center
SOM (%) = SOC (%) x
100
58
= SOC x 1.7241
CONVERSION OF SOC INTO SOM
The factor 1.7241 needs to be validated for site–specific situations

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Carbon Management and
Sequestration Center
CALCULATIONS OF SOIL C STOCK
1. (Weight of soil to a specific depth) x (C concentration)
2. (Area x Depth x Bulk Density ) x (C Concentration)
3. 0.1 m
= 24 Mg C/ha
x104 m2
ha
1.2 Mg
m3
2
102
x x
2
Bulk Density of SOM(0.2-0.5 Mg m -3 Must be Reported on Volume Basis

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Carbon Management and
Sequestration Center
Plowed
SOC Conc. = 1.5%
BD = 1.2 Mg/m3
Soil Mass10cm = 1200 Mg/ha
SOC Stock10cm = 18 Mg/ha
No Till
SOC Conc. = 1.5%
BD = 1.4 Mg/m3
Soil Mass10cm = 1400 Mg/ha
SOC Stock10cm = 21 Mg/ha
II. Suppose half of the land is plowed. Soil bulk density of the
plowed half has decreased to 1.2 Mg/m3 but SOC content is the
same. If the SOC stock is calculated on an equal depth basis, it is
lower in the plowed than in the unplowed field.

11. 11
Carbon Management and
Sequestration Center
SOIL MICROAGGREGATE FORMATION (<250 μm)
AND SOM STABILIZATION
(Redrawn from Tisdall and Oades, 1982. Soil Sci 33:141-163)
Clay
Clay
Clay
Clay
Clay
ClayClay
Clay
Clay
Clay
Clay
Clay
Clay
Clay
Clay
Clay
Organic Matter
O
OH
C
Fe
C
C
C
C
C
O
O
O
O
O
OH
OH
OH
OH
OH
Al
Ca
Strongly sorbed polymer Cation bridges

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Carbon Management and
Sequestration Center
CO2,N2O
CO2,CH4,N2O
GaseousEmissions
Stream
Top Soil
TRANSPORT, REDISTRIBUTION AND DEPOSITION OF SOIL ORGANIC CARBON ON AN
ERODED LANDSCAPE (LAL, 2016)
Delivery ratio is about 10%.
It decreases with increase in distance from the source.

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Carbon Management and
Sequestration Center
WATER MUDDIED WITH SEDIMENT FLOWS INTO THE OCEAN OFF GREENLAND
Credit: Nicolaj Kroeg Larsen, EOS 2019 100(5):5

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Carbon Management and
Sequestration Center
PERMANENCE
• The question of permanence is relevant.
• SOC sequestration in stable microaggregates can have a MRT
at a millennial scale.
• Thus, provision of incentives for continuous use of RMPs is a
key issue that needs to be addressed
Source: Lal (2016)

15. 15
Carbon Management and
Sequestration Center
THRESHOLD LEVEL OF SOIL ORGANIC MATTER IN 0-30CM LAYER
SOM : 2.5 - 3.5%
SOC : 1.5 - 2.0%
1.0 2.0 3.0 4.0
SOM (%)
CropYield(UseEfficiency)

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Carbon Management and
Sequestration Center
PAUCITY OF SCIENTIFIC DATA
• Research data on rate of SOC and SIC sequestration, soil C
sink capacity, effectiveness of RMPs for land use and
soil/crop/animal management, and the magnitude of SOC
sequestration and MRT are not widely available.
• While the importance of SOC pool to agronomic
sustainability has long been recognized (Jenny 1941), the
societal value of soil C needs to be determined (Lal 2014).
• SOC effects on productivity and use efficiency must be
determined for site-specific conditions.
• Global maps are needed for SOC and SIC stocks at
1:10,000 scale.
Source: Lal (2018)