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					    The Societal Value of Soil
      Carbon Sequestration


                   Rattan Lal
Director, Carbon Management and Sequestration Center
      The Ohio State University, Columbus, Ohio
      Global Climate Change

∆T over the 20th century…………. +0.6+0.2°C
Rate of ∆T increase since 1950…… +0.17°C/decade
Sea level rise over 20th century….. +0.1-0.2 m
Change in precipitation………….. +0.5-1%/decade
Extreme events……………………. +2-4%
                   ………..IPCC (2001)
Atmospheric Concentration of Trace Gases
        Between 1750 and 1999


                          Rate of increase   Radiative
  Gas    Concentration       Conc./yr         forcing
                                              (w/m2)
  CO2    280 - 367 ppm       1.5 ppm           1.46
  CH4    700 - 1745 ppb      7.0 ppb           0.48
  N2O    270 - 314 ppb       0.8 ppb           0.15
  CFCs     0 - 268 ppt       -1.4 ppt          0.34

IPCC (2001)
            Global Carbon Budget
 Activity                      1980-1989     1989-1998

                               -----------Pg C/y----------
 A. Source
  Fossil fuel emission         5.0 + 0.5      6.3 + 0.6
  Land us e change             1.7 + 0.8      1.6 + 0.8

 B. Sink
  Atmosphere                   3.3 + 0.2      3.2 + 0.2
  Ocean                        1.9 + 0.6      1.7 + 0.5
  Terrestrial/missing carbon   1.9 + 1.3      2.3 + 1.3
IPCC (2001)
    How Much C is in Soil?

(i) Soil organic C     = 1550 Pg
     Soil inorganic C  = 750 Pg
     Total             = 2300 Pg
(ii) Atmosphere        = 720 Pg
(iii) Biota            = 560 Pg
(iv) Ocean             = 38,000 Pg
• SOC pool = 40 - 100 Mg/ha
     Soil vs. Atmospheric C


1 Pg (billion tonnes) of soil C = 0.47 ppm
  of CO2
      Mean Residence Time of C in
            Different Pools
The average atom of C spends about:
• 5 yrs in the atmosphere,
• 10 yrs in vegetation (including trees),
• 35 yrs in soil, and
• 100 yrs in the sea.
Residence time = pool / flux
The residence time is longer in soils of high
  latitude.
ra
 Effects of Soil Erosion and Redistribution on
             Trace Gases Emissions.
      CO2
            CO2
                     CH4 N2O



Depressed                       CH4 N2O
oxidation of CH4
                   C burial




        Erosion                C burial
        Redistribution                    DOC
        Depression
       Soil erosion and C emission


Land              Area Emission Reference
                 (Mha) (Pg C/ yr)
World cropland    1500    0.32   Jacinthe & Lal (2001)
World soils      13,048    1.1   Lal (1995)
                                       1.14 x 1015 g/yr
                                       decomposition
               1500 x 1015             and emission to
     C
               C in world              the atmosphere     3.99 x 1015 g/yr stored
sequestratio
               soil                                       within the terrestrial
n
                                                          ecosystem
                   5.7 x 1015 g/yr C
                   displaced due to
                   erosion



                                                           0.57 x 1015 g/yr
                                                           transported to
                                                           the ocean

 Global soil erosion and dynamics of soil organic carbon
 (Lal, 1995).
 Historic Soil C Loss


World soils…….. 66-90 Pg
U.S. soils……….. 5 Pg

Recoverable C…. 50-75%
Time horizon……25-50 yrs
    The magnitude of soil C loss

              30-40 Mg/ha
Agricultural soils now contain lower SOC pool
 than their potential, and thus have a C sink
 capacity.
Anthropogenic emissions (1850-2000)


  1. Fossil fuel:     270 + 30 Pg
  2. Land use change: 136 + 55 Pg
       Soil:          78 + 12
    Soils and Global Warming


Can we use soils and vegetation for
 scrubbing a dirty atmosphere?
     Carbon Sequestration

It is the net removal of CO2 from
  the atmosphere into the long-lived
  pools of C such as vegetation and
  soil by biotic and abiotic
  processes.
   A New Definition of Agriculture


It is an anthropogenic manipulation of
  carbon through: uptake, fixation,
  emission and transfer.

           CU + CF = CE + CT
  How to Increase Soil C

A. Increase
  (i) density of C in the soil
  (ii) depth of C in the profile
B. Decrease
  (i) decomposition of C
  (ii) losses due to erosion
 Increasing Density of C in Soil
Plow                      No till
Residue removed           Residue return
Bare fallow               Cover crops
Low input                 Judicious input
                          (precision farming, IPM)
No water control          Water conservation and
                          supplemental irrigation
Fence to fence cropping   Forestation/vegetation on
                          marginal lands/CRP
Disposition of Organic Residues
                   CO2




                            60-80%

Organic residues
  100 grams


    3-8%            3-8%          10-30%

          Biomass          Nonhumic        Complex
      (soil organisms)    compounds         humic
                         (polyuronides,   compounds
                           acids, etc.)
                                  Humus
                                  10-35%
 Mulch Rate and SOC Content in Ohio

No till:
SOC (Mg ha-1) = 15.2 + 0.321 M   R = 0.68

Plow till:
SOC (Mg ha-1) = 11.9 + 0.266 M   R = 0.72
     Cover Crop and SOC Pool in a
         Miamian Soil in Ohio
Treatment             SOC (0-30 cm)   Relative SOC
                         Kg/m3            (5 yr)

Continuous corn           2.30            100
Corn-soybean              2.34            102
Continuous soybean        2.37            103
Corn-soybean-wheat        2.36            103
Alfalfa                   2.33            101
Birdsfoot trefoil         2.45            107
White clover              2.36            103
Kentucky blue grass       2.28            103
Tall fescue               2.72            118
Smooth bromegrass         2.75            120
Fallow                    2.58            112
Lal (1998)
SOC pool in 0-30 cm depth over a 60-year period at
     Coshocton, OH (Hao, Lal, Owen, 2002)


      Management                       SOC pool     Rate
                                       (Mg C/ha) (Kg C/ha/yr)
      Conventional tillag e              24.5         --
      Conventional tillag e-rotation     29.7        87
      Chisel tillage (C-S)               32.1        127
      No tillage (C-S)                   36.8        205
      No tillage (C-C)                   39.6        252
      No tillage (C-C)+manure            65.5        683
   Biofuel vs. Fossil Fuel


1 gallon of biofuel = 0.5 gallon of
  oil/diesel saving
   Global Cooling Potential

GCP = (GWP)-1
• Conservation tillage
                               100-1000
• Cover crops                  Kg C/ha/y
• Nutrient management
• Soil restoration
• CRP/WRP
• Land use and afforestation
Land Use and Soil C Sequestration in the U.S.

    Land use       Area     Net potential

                   Mha      MMTC/yr
    Cropland       156.9    75-208
    Grazing land   285.9    81-91
    Forest land    236.1    49-186
    CRP            13.8     9.7-14.6
    WRP            0.6      0.5-0.9
    Urban          20.6     2.2-8.6
    Total          713.9    154-509 (332)
U.S. Emissions and Soil C Sequestration


• Total U.S. gas emissions……………….1500 MMTC/yr
• Emission from agricultural activities…133 MMTC/yr
• Net soil C sequestration potential……..332 MMTC/yr
         Agricultural Soils and
          Mitigation of GHE

1 bbl of diesel = 220 L
1 L of diesel = 0.73 Kg C
 1 ton of C = 1370 L of diesel = 6.2 bbl of
  diesel
C sequestration potential of ag soils = 2 billion
  barrels/yr
Potential of Global Soil C Sequestration


              1-2 Pg C/yr or
  24% of the total emissions by fossil fuel
                combustion.
Is Soil C Sequestration A Free Lunch?


  • Not really!
  • Additional N, P, S etc. are needed for
    humification of residue C.
  • There are hidden C costs of RMPs.
    Building Blocks of Humus

• C is only one of several constituents of
  humus.
• Other constituents are H, O, N, P, S and
  micronutrients.
  Nutrients Needed for Humification


• How much N, P and S are needed to
  convert residue into humus?
• How to adjust fertilizer use for desired
  productivity and converting residue into
  humus?
Elemental Composition of Humus and
           Crop Residues

Ratio         Humus     Crop Residue

C:N            10-15      70-100
C:P            40-60      200-400
C:S            60-80      400-800
Additional Nutrients Required to Convert
    10,000kg of Carbon into Humus


  Nutrient            Quantity needed
                           (kg)
  N                        833
  P                        200
  S                        143
       Energy-based Input and C
            Sequestration
1. What is the carbon budget in relation to:
    (i) Fertilizer use
    (ii) Manure application
    (iii) Tillage practices
    (iv) Irrigation
    (v) Liming of acid soils
2. C sequestration occurs only if output > input.
Hidden C costs of tillage
       methods
Method                 Kg C/ha/yr

Conventional tillage   62-72
Minimum tillage        40-45
No tillage             20-23
Hidden C cost of fertilizers

Fertilizer type   Kg C/kg of fertilizer

Nitrogen                   0.86
P2O5                       0.17
K2O                        0.12
Lime                      0.0.36
Hidden C cost of pesticides

 Pesticide      Kg C/kg of pesticide

 Herbicides             4.7
 Fungicides             5.2
 Insecticides           4.9
Hidden C cost of irrigation

   Method      Kg C/ha/yr

   Pump        140-160
   Gravity     0
       Farming Carbon



1. Commodification of C (price)
2. Incentives
   Societal Value of Carbon


Nutrients and H2O contained in 1 kg of
 humus = $0.2

Rational price = $200/ton
   Undervaluing a Commodity


Undervaluing carbon has and will
 perpetuate its misuse.
Cumulative C sequestration (M/ha)   40


                                    30



                                    20



                                    10


                                    0
                                         0   10        20       30        40    50

                                                  Time after conversion (yrs)
     Economics of C Sequestration


1. Assessing economics of C by itself is not
   adequate.
2. Evaluate the entire package of benefits:
   (i) To the farmer
   (ii) To the society
Can soil C sequestration mitigate
     the greenhouse effect?
        Dependency on Carbon


Modern civilization is hooked on carbon. It
 needs rehabilitation, in a big way.
Role of soil and biomass C in global C management.
Source: The Global Energy Technology Strategy, Battelle, Washington, D.C., 1998
          Soil C Sequestration


• It is a:Development challenge in the tropics
  and sub-tropics.
• Policy reform and implementation challenge
  in developed countries.
        A Bridge to the Future
• C sequestration in soil and vegetation is a
  bridge to the future.
• It buys us time while alternatives to fossil
  fuel take effect.
• It is a good thing to do, regardless of what
  happens to the climate.
        It is truly a win-win strategy.

				
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