1. Crop Residues and Soil Carbon
Rattan Lal
Carbon Management and Sequestration Center
The Ohio State University
Columbus, OH 43210

2. Estimates of Crop Residues Production in the U.S.
Species
1991
2001 Mg
Cereals
325
367`
Legumes 58 82
Oil Crops 17 20
Sugar Crops 25 14
Tubers 5
Total
430
488
(Lal, 2005)

3. Estimates of Crop Residues Production in the World
Species
1991
2001 Mg
Cereals
2563
2802
Legumes
238
305
Oil Crops
162
108
Sugar Crops
340
373
Tubers
145
170
Total
3448
3758
(Lal, 2005)

4. Crop Residue and Ecosystem Services
Biofuel
Animal Feed
Industrial Raw Material
Soil Quality Improvement
Traditional
Erosion Control
Nutrient Cycling
Modern Liquid Biofuels
Agronomic/Biomass Productivity and Sustainability
Soil Biodiversity
Water Management
Soil Structure & Tilth
Carbon Sequestration
Crop residues have numerous competing uses, such as removal for biofuel production, animal feed, industrial raw material or returned to soil as an amendment.
Soil application of crop residues as amendment is necessary to enhance/maintain soil quality and sustain agronomic productivity.

5. Competing Uses of Crop Residues
Feed
Fuel
Fiber
Construction material

6. Slope-Soil Loss Relations for Different Mulch Rates (Lal, 1976)
Equation
Average (Mg/ha)
Relative Loss
0.81
Y = 11.8 S1.13
76.60
851 2
0.35
Y = 0.5 S0.87
2.40 27 4
0.57
Y = 0.07 S1.05
0.37 6
0.46
Y = 0.01 S1.0
0.09 1
No-till
0.36
Y = 0.01 S0.5

7. Energy in Biomass One Mg of Corn Stover = 280 L of Ethanol
GJ of Energy
16 x 106 BTU
2 Barrels of Diesel
3 x 106 KCal
(Lal, 2005)

16. Estimates of Traditional Biofuel Use in India and Asia in 1995
Country/Region
Fuel wood
Cattle Dung
Crop Residue
Total
Range Average
Tg C yr
India
374
Asia
1018
World
2324

17. Biofuel From Industrial CO2 Application on Ag. Soils
and SOC Sequestration
Bioenergy
Bioreactors
Algae
Algae
Ethanol
Biodiesel
Biochemicals
Residues
Nutrient-
Enriched & Biochar/
Compost
Cynobacteria
Cynobacteria
Soil Carbon Sequestration
Application on Ag. Soils

18. Strategic Questions
Should crop residues be used for carbon sequestration and soil quality improvement or producing energy?
Should the answer to this question be determined by short-term economics or the long-term sustainability of natural resources?
Should the need for fuel override the urgency to achieve global food security?

19. Soil Carbon Dynamics Depletion : Cinput < Coutput
Sequestration: Cinput > Coutput

20. Innovative Technology II Innovative Technology I
Soil C Dynamics 20 40 60 80
100
120
140
160
Time (Yrs)
Innovative Technology II
Innovative Technology I
Subsistence farming, none or low off-farm input soil degradation
New
equilibrium
Adoption of RMPs
Maximum Potential
Rate ΔY ΔX
Attainable
Potential
Accelerated erosion

21. Recommended Management Practices and Soil Carbon
Recommended practices
C sequestration potential
(Mg C/ha/yr)
Conservation tillage
Winter cover crop
Soil fertility management
Elimination of summer fallow
Forages based rotation
Use of improved varieties
Organic amendments
Water table management/irrigation
Lawn & Turf
Minesoil reclamation
Lal et al., 1998

22. Terrestrial C Sink Capacity
Historic Loss from Terrestrial Biosphere = 456 Pg with 4 Pg of C emission = 1 ppm of CO2
The Potential Sink of Terrestrial Biospheres = 114 ppm
Assuming that up to 50% can be resequestered = 45 – 55 ppm
The Average Sink Capacity = 50 ppm over 50 yr.

23. Potential of Mitigating Atmospheric CO2
(Hansen, 2008)

24. Estimates of Global and Regional Potential of Soil C Sequestration
Potential Tg C/yr
World: – 1200
USA: – 432
India: 40 – 50
Iceland 1.2 – 1.6
Brazil: 40 – 60
W. Europe: 70 – 190
China: – 364

25. Crop yield and productivity effects of SOC pool
Fertilized
Unfertilized
Crop Yield
∆ Yield
SOC Pool
SOC Pool

26. Microbial biomass
Nutrient Retention
Available water capacity
Aggregation
Infiltration rate
Aeration porosity
Soil Quality
SOC Pool

27. Agronomic productivity
WUE
NUE
EUE
Soil Quality
SOC Pool

28. Soil Quality
Erodibility
Crusting
Compaction
Runoff
SOC Pool

29. Economics of Residue Removal for Biofuel

30. Production Increase (106 Mg yr-1)
Increase in Food Production in LDCs by Increasing SOC Pool by 1 Mg C ha-1 yr-1
Crop
Area (Mha)
Production Increase (106 Mg yr-1)
Cereals
430
Legumes 68
Tubers 34
Total
532

31. Food Insecure People
Africa = 200 million
World = 800 million

32. Food Gap by Region Region Food Gap 2000 2010 - - 106Mg yr -1 - -
Mg yr
Sub-Saharan Africa
10.7
17.5
Latin America
0.6
1.0
Asia
1.7
3.6
Others
0.2
Total (67 Countries)
13.2
22.3
(Shapouri, 2005)

33. Commodification of soil C
How can soil C be made a commodity that can be traded like any other farm product?

34. The value of soil carbon
Value to farmer: for soil quality enhancement
Value to society: for ecosystem services

35. Societal value of soil carbon
Reduction in erosion and sedimentation of water bodies.
Improvement in water quality.
Biodegradation of pollutants.
Mitigation of climate change.

36. On-farm value of soil carbon
The quantity of NPK, Zn, Cu etc. and H2O retention in humus.
Improvements in soil structure and tilth.
Decrease in losses due to runoff, leaching and erosion.
~ $200/ton

37. 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.

38. Trading C Credits
The C market may reach $ trillion by We need to make this market accessible to land managers.

39. Challenges to Trading Soil Carbon Credits
Aggregating small land holders (1-5 acre farm size) to make a meaningful transaction of 100,000 t C/yr
Assessing net increase in soil C pool on annual basis over a country/district level.
Determining the societal value of soil C (~$250/t)
Paying farmers a just/fair value
Minimizing transaction costs

40. Sustainable Management of Soils
Use of crop residues as soil amendments is essential so that:
soil quality is progressively restored rather than diminished.
soil organic carbon pool is enriched rather than depleted.
susceptibility to erosion and other degradation processes is reduced rather than exacerbated. and
agronomic/biomass productivity per unit input and time is increased rather than reduced or plateaued.

41. Ten Options of Sustainable Management of Soils
Retain crop residue as mulch.
Adopt no-till farming.
Include leguminous cover crops in the rotation cycle.
Maintain a positive nutrient balance INM (e.g., manure, compost).
Use precision farming/site specific management.

42. Ten Options (continued)
Conserve water through sub/drip irrigation and water harvesting.
Restore marginal/degraded/desertified soils.
Grow improved/GM plants along with agroforestry measures.
Integrate principles of watershed management.
Restore wetlands.

43. Ultimate Goal of Soil Management
The strategy is to:
Adopting RMPs where extractive farming practices are widely used.
Enhancing SOC pool through use of residue mulch and manures where soil has been traditionally mined for millennia.
Using INM (Manure, biosolids BNF, fertilizers) to achieve positive nutrient balances, where negative balances have occurred, and
Making agriculture and soil a solution rather than cause of the environmental problem.

44. Sustainability of a Land Use System
CNPP
S1 = n
(Σ Ci)
i = 1
S1 = Sustainability index of a land use system
CNPP = C output as net primary productivity
Ci = C input from all factors of production

45. A Precious Resource
Irrespective of the climate debate, soil quality and its organic matter content must be restored, enhanced and improved.