FAO Status and Challenges of Soil Carbon Sequestration
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The document discusses the status and challenges of global soil carbon sequestration, highlighting various components of the soil carbon pool and their potential for carbon management. It emphasizes the need for precise measurements and data to support trading of carbon credits, and the importance of understanding soil organic carbon's impact on agronomic sustainability. The document also calls for further research to fill data gaps regarding soil carbon dynamics and its societal value.
FAO Status and Challenges of Soil Carbon Sequestration
- 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
- 3. 3 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
- 4. 4 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)
- 5. 5 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
- 7. 7 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)
- 8. 8 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
- 9. 9 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
- 10. 10 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
- 12. 12 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.
- 13. 13 Carbon Management and Sequestration Center WATER MUDDIED WITH SEDIMENT FLOWS INTO THE OCEAN OFF GREENLAND Credit: Nicolaj Kroeg Larsen, EOS 2019 100(5):5
- 14. 14 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)
- 16. 16 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)