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  1. 1. Crop Residues and Soil Carbon<br />Rattan Lal<br />Carbon Management and Sequestration Center<br />The Ohio State University<br />Columbus, OH 43210<br />
  2. 2. Estimates of Crop Residues Production in the U.S.<br />(Lal, 2005)<br />
  3. 3. Estimates of Crop Residues Production in the World<br />(Lal, 2005)<br />
  4. 4. Crop Residue and Ecosystem Services<br />Biofuel<br />Animal Feed<br />Industrial Raw Material<br />Soil Quality Improvement<br />Traditional<br />Erosion Control<br />Nutrient Cycling<br />Modern Liquid Biofuels<br />Agronomic/Biomass Productivity and Sustainability<br />Soil Biodiversity<br />Water Management<br />Soil Structure & Tilth<br />Carbon Sequestration<br />Crop residues have numerous competing uses, such as removal for biofuel production, animal feed, industrial raw material or returned to soil as an amendment. <br />Soil application of crop residues as amendment is necessary to enhance/maintain soil quality and sustain agronomic productivity.<br />
  5. 5. Competing Uses of Crop Residues<br /><ul><li> Feed
  6. 6. Fuel
  7. 7. Fiber
  8. 8. Construction material</li></li></ul><li>Slope-Soil Loss Relations for Different Mulch Rates (Lal, 1976)<br />
  9. 9. Energy in Biomass<br />One Mg of Corn Stover =<br /><ul><li> 280 L of Ethanol
  10. 10. 15 - 18 GJ of Energy
  11. 11. 16 x 106 BTU
  12. 12. 2 Barrels of Diesel
  13. 13. 3 x 106 KCal</li></ul>(Lal, 2005)<br />
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  22. 22. Estimates of Traditional Biofuel Use in India and Asia in 1995<br />
  23. 23. Biofuel From Industrial CO2 <br />and SOC Sequestration<br />Bioenergy<br />Bioreactors<br />Algae<br />Algae<br />Ethanol<br />Biodiesel<br />Biochemicals <br />Nutrient-<br />Enriched & Biochar/<br />Compost<br />Residues<br />Cynobacteria<br />Cynobacteria<br />Soil Carbon Sequestration<br />Application on Ag. Soils<br />
  24. 24. Strategic Questions<br />Should crop residues be used for carbon sequestration and soil quality improvement or producing energy?<br />Should the answer to this question be determined by short-term economics or the long-term sustainability of natural resources?<br />Should the need for fuel override the urgency to achieve global food security?<br />
  25. 25. Soil Carbon Dynamics<br />Depletion : Cinput < Coutput<br />Sequestration: Cinput > Coutput<br />
  26. 26. Soil C Dynamics<br />Innovative Technology II<br />Innovative Technology I<br />100<br />Maximum Potential<br />80<br />Rate<br />Attainable <br />Potential<br />ΔY<br />60<br />ΔX<br />Accelerated erosion<br />40<br />20<br />0<br />40<br />60<br />80<br />100<br />120<br />140<br />160<br />20<br />Time (Yrs)<br />Subsistence farming, none or low off-farm input soil degradation<br />New <br />equilibrium<br />Adoption of RMPs<br />
  27. 27. Recommended Management Practices and Soil Carbon<br />Lal et al., 1998<br />
  28. 28. Terrestrial C Sink Capacity<br />Historic Loss from Terrestrial Biosphere = 456 Pg with 4 Pg of C emission = 1 ppm of CO2 <br />The Potential Sink of Terrestrial Biospheres = 114 ppm <br />Assuming that up to 50% can be resequestered = 45 – 55 ppm<br /><ul><li> The Average Sink Capacity = 50 ppm over 50 yr.</li></li></ul><li>Potential of Mitigating Atmospheric CO2<br />(Hansen, 2008)<br />
  29. 29. Estimates of Global and Regional Potential of Soil C Sequestration<br />Region<br />Potential Tg C/yr <br />World: 600 – 1200<br />USA: 144 – 432<br />India: 40 – 50<br />Iceland 1.2 – 1.6<br />Brazil: 40 – 60<br />W. Europe: 70 – 190<br />China: 126 – 364<br />
  30. 30. Crop yield and productivity effects of SOC pool<br />Fertilized<br />Unfertilized<br />∆ Yield<br />Crop Yield<br />SOC Pool<br />SOC Pool<br />
  31. 31. Microbial biomass<br />Nutrient Retention<br />Available water capacity<br />Aggregation<br />Infiltration rate<br />Aeration porosity<br />Soil Quality<br />SOC Pool<br />
  32. 32. Agronomic productivity<br />WUE<br />NUE<br />EUE<br />Soil Quality<br />SOC Pool<br />
  33. 33. Soil Quality<br />Erodibility<br />Crusting<br />Compaction<br />Runoff<br />SOC Pool<br />
  34. 34. Economics of Residue Removal for Biofuel<br />
  35. 35. Increase in Food Production in LDCs by Increasing SOC Pool by 1 Mg C ha-1 yr-1<br />
  36. 36. Food Insecure People<br />Africa = 200 million<br /> World = 800 million<br />
  37. 37. Food Gap by Region <br />(Shapouri, 2005)<br />
  38. 38. Commodification of soil C<br />How can soil C be made a commodity that can be traded like any other farm product?<br />
  39. 39. The value of soil carbon<br />Value to farmer: for soil quality enhancement<br />Value to society: for ecosystem services<br />
  40. 40. Societal value of soil carbon<br />Reduction in erosion and sedimentation of water bodies.<br />Improvement in water quality.<br />Biodegradation of pollutants.<br />Mitigation of climate change.<br />
  41. 41. On-farm value of soil carbon<br />The quantity of NPK, Zn, Cu etc. and H2O retention in humus.<br />Improvements in soil structure and tilth.<br />Decrease in losses due to runoff, leaching and erosion.<br />~ $200/ton<br />
  42. 42. Need for determining a just value of soil carbon<br />Under valuing a resource can lead to its abuse.<br />It is important to identify criteria for determining the societal value of soil C, and using it for trading purposes.<br />
  43. 43. Trading C Credits<br /> The C market may reach $ trillion by 2020. We need to make this market accessible to land managers.<br />
  44. 44. Challenges to Trading Soil Carbon Credits<br />Aggregating small land holders (1-5 acre farm size) to make a meaningful transaction of 100,000 t C/yr<br />Assessing net increase in soil C pool on annual basis over a country/district level.<br />Determining the societal value of soil C (~$250/t)<br />Paying farmers a just/fair value<br />Minimizing transaction costs<br />
  45. 45. Sustainable Management of Soils<br /> Use of crop residues as soil amendments is essential so that:<br /><ul><li>soil quality is progressively restored rather than diminished.
  46. 46. soil organic carbon pool is enriched rather than depleted.
  47. 47. susceptibility to erosion and other degradation processes is reduced rather than exacerbated. and
  48. 48. agronomic/biomass productivity per unit input and time is increased rather than reduced or plateaued.</li></li></ul><li>Ten Options of Sustainable Management of Soils<br />Retain crop residue as mulch.<br />Adopt no-till farming.<br />Include leguminous cover crops in the rotation cycle.<br />Maintain a positive nutrient balance INM (e.g., manure, compost).<br />Use precision farming/site specific management.<br />
  49. 49. Ten Options (continued)<br />Conserve water through sub/drip irrigation and water harvesting.<br />Restore marginal/degraded/desertified soils.<br />Grow improved/GM plants along with agroforestry measures.<br />Integrate principles of watershed management.<br />Restore wetlands.<br />
  50. 50. Ultimate Goal of Soil Management<br /> The strategy is to:<br />Adopting RMPs where extractive farming practices are widely used.<br />Enhancing SOC pool through use of residue mulch and manures where soil has been traditionally mined for millennia.<br />Using INM (Manure, biosolids BNF, fertilizers) to achieve positive nutrient balances, where negative balances have occurred, and<br />Making agriculture and soil a solution rather than cause of the environmental problem.<br />
  51. 51. Sustainability of a Land Use System<br />CNPP<br />S1 =<br />n<br />(Σ Ci)<br />i = 1<br />S1 = Sustainability index of a land use system<br />CNPP = C output as net primary productivity<br />Ci = C input from all factors of production<br />
  52. 52. A Precious Resource<br />Irrespective of the climate debate, soil quality and its organic matter content must be restored, enhanced and improved.<br />