Carbon Sequestration. Soil Carbon and Atmospheric CO 2. Scope and Potential of Agricultural Soils to Mitigate Climate Change

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1 Scope and Potential of Agricultural Soils to Mitigate Climate Change Carbon Sequestration Capture and secure storage of atmospheric C that would otherwise be emitted or remain in the atmosphere R. Lal Carbon Management and Sequestration Center The Ohio State University Columbus, OH USA C sequestration is important because: i. There are no yet non-c C fuel sources, ii. There is a need to stabilize atmospheric abundance of CO 2, iii. We must restore/improve ecosystem services, and iv. Advance global food security Technological options for carbon sequestration in terrestrial ecosystems Biomass Carbon in Forest Biotic Pool = 600 Pg Species selection Site preparation Nutrient management Stand management Urban forests SOC Pool = 1550 Pg Biofuel plantations Species selection Soil type Composting by-products Carbon Sequestration in Terrestrial Ecosystems Wetland Management Water table management Sediment control in the watershed Enhancing plant biodiversity Soil C Farming Erosion control Conservation tillage Cover cropping and mulch farming Manuring and INM Agroforestry Controlled grazing C-MASC Lawns and Turfs SIC Pool = 950 Pg Soil Carbon and Atmospheric CO 2 4 Pg of soil C = 1 ppm Terrestrial C Sink Capacity Historic Loss from Terrestrial Biosphere = 456 Pg with 4 Pg of C emission = 1 ppm of CO 2 The Potential Sink of Terrestrial Biospheres = 114 ppm Assuming that up to 50% can be resequestered = ppm The Average Sink Capacity = 50 ppm over 50 yr.

2 Potential of Mitigating Atmospheric CO 2 (Hansen, 2008) Estimates of Global and Regional Potential of Soil C Sequestration Region Potential Tg C/yr 1. World: USA: India: Iceland Brazil: W. Europe: China: Subsistence farming, none or low off-farm input soil degradation New equilibrium Adoption of RMPs Maximum Potential Rate ΔY Attainable Potential ΔX Accelerated erosion Innovative Technology II Innovative Technology I RELATIVE RISKS Ocean iron fertilization Sulfur particles in the stratosphere Electrochemical weathering Mirrors In space 20 Biomass with carbon capture Air capture/solvent regeneration 0 Reduction in greenhouse gas emissions RELATIVE COST C-MASC Time (Yrs) Importance of Soil Organic Carbon 1. Improves soil structure and tilth 2. Reduces soil erosion 3. Increases plant available water 4. Stores plant nutrients 5. Provides energy for soil fauna 6. Purifies water 7. Denatures pollutants 8. Increases biodiversity 9. Improves crop/biomass yields 10. Moderates climate It makes soil a living ecosystem It is a nation s most precious natural resource Ancillary Benefits of Soil/Terrestrial Carbon Sequestration 1. Improved quality of soil and water resources 2. Decreased nutrient loss from ecosystem 3. Reduced soil erosion 4. Better wild life habitat 5. Increased water conservation 6. More biomass productivity 7. Advance food security 8. Restoration of degraded ecosystems 9. Low/no cost 10. Increase NUE and WUE

3 Economics of Residue Removal for Biofuel Economics of Residue Removal for Biofuel Estimated Increase in Food Production in Africa by Increase in SOC Pool by 1 Mg C/ha/yr (Lal, 2006) Type Total Annual Increase (10 6 Mg/yr) Grains Roots and Tubers Total C : N, C : P and C : S Ratio of Crop Residues and Humus Nutrients and Residue Required to Sequester 100 kg of Soil Carbon Nutrients Residues Humus C : N C : P C : S N kg P kg S kg C kg (10% efficiency, 2500 kg of residue) Thus, there is a need to supply, N, P, S and other elements. Sequestration of 10 Mg of C in Humus Carbon: residues Nitrogen: Phosphorous: Sulfur: 28 Mg C or 62 Mg of oven dry crop 833 kg 200 kg 142 kg Total amount of humus produced = 17.2 Ten Options of Sustainable Management of Soils 1. Retain crop residue as mulch. 2. Adopt no-till farming. 3. Include leguminous cover crops in the rotation cycle. 4. Maintain a positive nutrient balance INM (e.g., manure, compost). 5. Use precision farming/site specific management. Mg = + 0.7% increase in SOC in 20-cm layer.

4 Ten Options (continued) 6. Conserve water through sub/drip irrigation and water harvesting. 7. Restore marginal/degraded/desertified soils. 8. Grow improved/gm plants along with agroforestry measures. 9. Integrate principles of watershed management. Soil C as an Indicator of Climate Change There are numerous advantages: 1. It is a familiar property, 2. It involves direct measurement, 3. It can be measured in 4 dimensions (length, width, depth, time), 4. It lends itself to repeated measurements over the same site, 10. Restore wetlands. Soil C as an Indicator of Climate Change (Contd.) 5. It is linked to ecosystem performance and services, 6. It is a key driver of soil formation, 7. It is important to soil fertility, 8. It has memory, 9. It has well defined properties, Soil C as an Indicator of Climate Change (Contd.) 10. It can be used in synergism with other indicators, 11. Its uncertainty can be quantified, 12. Its pathways across the landscape can be followed, 13. It is an important archive of paleoenvironmental conditions. Researchable Issues 1. Methods of measurement of SOM pool at landscape, watershed or regional scales 2. Baseline 3. Climate change and SOM 4. Fate of soil transported by erosional processes 5. SOM Management and C Sequestration 6. Nutrient Management 7. Issues with No-Till Farming 8. SOM pool and crop yield 9. Validating models of SOM pool under changing climate 10. Commodification and societal value of SOM Measurement of SOM I. The SOM concentration has been measured by soil scientists since the 1860s. Boussingault and Levy (1852, 1853) E. Wolf (1864) Van Bemmelen (1896) II. CO 2 evolution from soil was first measured in 1794 Ingen-Housz (1794) Seee articles by Christian Feller

5 Measurement of SOM for Soil Fertility Purposes Adequacy of the Conventional Methods of Measuring SOM Quantity: Concentration (%, g/kg) Depth: Plow depth (0-20 cm) Frequency: The rotation cycle (1 to 3 yrs) Precision: One decimal place when expressed as % Scale: Plot scale, pedon scale Both wet and dry combustion methods have been adequate for the purpose of assessing managementinduced changes in SOC concentration in the plow depth. Measurement of SOM for Mitigating Climate Change How can we measure SOC pool: Accurately, transparently, verifiably, and economically, Over a landscape, watershed or a region, Changes over 1 to 2 year period, and Atmospheric concentration of CO 2 (ppmv) Carbon sequestration With reference to baseline Year Specific Needs for Trading Carbon Credits Quantity: SOC pool (Mg C/ha) Depth: 1-m or more Frequency: 1-2 yrs depending on land use Precision: Whole # in Mg/ha Scale: Landscape or farm scale Importance of Soil Bulk Density Assessment of SOC pool cannot be made without the knowledge of soil bulk density for each of the layers. Conclusions made on C sequestration on the basis of SOC concentration can be erroneous.

6 Change in SOC concentration of a degraded rainforest soil at Le Selva, Costa Rica by plantation of native trees (recalculated from Fisher, 1998). Change in SOC pool of a degraded rainforest soil at Le Selva, Costa Rica by plantation of native trees (recalculated from Fisher, 1998). Species Control (pasture) Virola Koschnyi Stryphnodendron microstachyum Vochysia guatemalensis Pithecellobium macradenium Pinus tecunumanii Hieronyma alchorneoides Gmelina arbora Vochysia ferruginea Inga edulis Acacia mangium Pentaclethra macroloba SOC concentration in 0-15 cm layer (g/kg) Initial 3 years after Change (%/yr) Species Control (pasture) Virola Koschnyi Stryphnodendron microstachyum Vochysia guatemalensis Pithecellobium macradenium Pinus tecunumanii Hieronyma alchorneoides Gmelina arbora Vochysia ferruginea Inga edulis Acacia mangium Pentaclethra macroloba SOC pool in 0-15 cm layer (Mg C/ha) Initial years after Rate of change (Mg C/ha/yr) Emerging Technologies to Directly Measure SOC Pool LIBS INS (Measures on volume basis) Infrared Near infrared Researchable Issues 1. Methods of measurement of SOM pool at landscape, watershed or regional scales 2. Climate change and SOM 3. Fate of soil transported by erosional processes 4. SOM Management and C Sequestration 5. SOM pool and crop yield 6. Validating models of SOM pool under changing climate 7. Commodification and societal value of SOM COMMODIFICATION OF SOIL C THE VALUE OF SOIL CARBON How can soil C be made a commodity that can be traded like any other farm product? Value to farmer: for soil quality enhancement Value to society: for ecosystem services

7 SOCIETAL VALUE OF SOIL CARBON Reduction in erosion and sedimentation of water bodies. Improvement in water quality. Biodegradation of pollutants. Mitigation of climate change. ON-FARM VALUE OF SOIL CARBON The quantity of NPK, Zn, Cu etc. and H 2 O retention in humus. Improvements in soil structure and tilth. Decrease in losses due to runoff, leaching and erosion. ~ $200/ton NEED FOR DETERMINING A JUST VALUE OF SOIL CARBON Under valuing a resource can lead to its abuse. It is important to identify criteria for determining the societal value of soil C, and using it for trading purposes. TRADING C CREDITS The C market may reach $ trillion by We need to make this market accessible to land managers. Not Taking Soils for Granted If soils are not restored, crops will fail even if rains do not; hunger will perpetuate even with emphasis on biotechnology and genetically modified crops; civil strife and political instability will plague the developing world even with sermons on human rights and democratic ideals; and humanity will suffer even with great scientific strides. Political stability and global peace are threatened because of soil degradation, food insecurity, and desperateness. The time to act is now. Lal (Science, 2008)