AssessingSoil Carbon Sequestration

Alan J.Franzluebbers

Ecologist

Watkinsville GA

TN

MSAL

GA

FL

VA

NC

SC

MD

…in the southeastern USA and beyond

Carbon Cycle

AtmosphericCO2

Plantrespiration

Animalrespiration

Soil respiration

Photosynthesis

Soilorganisms

Soilorganicmatter

DissolvedCO

in water2

Leachate

AtmosphericN2

Mineralization

Denitrification

BiologicalN fixation

Carbonateminerals

Fossil fuels

CO2

NN ON

2

2

O

NHvolatilization

3

NHfixation

4

Plantuptake

Fertilizer

CarbonInput

CarbonOutput

SoilCarbon

Sequestration

Carbon Cycle

Focus on maximizing carbon input

Management Approaches

Integrated management• Pest control• Crop / livestock systems

ARS Image Number K5141-4

Plant selection• Species, cultivar, variety• Growth habit (perennial / annual)• Rotation sequence• Biomass energy crops

Tillage• Type• Frequency

Fertilization• Rate, timing, placement• Organic amendments

Focus on minimizing carbon loss from soil

ARS Image Number K7520-2

Management Approaches

Reducing soil disturbance• Less intensive tillage• Controlling erosion

Utilizing available soil water• Promotes optimum plant growth• Reduces soil microbial activity

Maintaining surface residue cover• Increased plant water use and

production• More fungal dominance in soil

ProductivitySoil

OrganicMatter

Water relations BiodiversityNutrient cycling

Greenhouse gasmitigation

Soil Organic MatterValues and ecosystem services

Minimal disturbance of the soil surface is critical in avoiding soil organic matter loss from erosion and microbial decomposition

Soil Carbon Sequestration

Soil Carbon SequestrationTillage influence on depth distribution of crop residues

Data from Allmaras et al. (1996) Soil Sci. Soc. Am. J. 60:1209-1216

Proportion of Oat Residue Applied (%)0 10 20 30 40 50 60

SoilDepth(cm)

-30

-24

-18

-12

-6

0

Moldboard plow(inversion tillage)

Proportion of Oat Residue Applied (%)0 10 20 30 40 50 60

SoilDepth(cm)

-30

-24

-18

-12

-6

0

Moldboard plow(inversion tillage)

Chisel plow(non-inversiontillage)

Soil Carbon SequestrationDepth distribution of crop residues without tillage

Data from Ortega et al. (2002) Agron. J. 94:944-954

Crop Residue (Mg . ha-1)

0 1 2 3 4 5

SoilDepth(cm)

-10

-8

-6

-4

-2

0

NT wheat-fallow

OnSurface

Crop Residue (Mg . ha-1)

0 1 2 3 4 5

SoilDepth(cm)

-10

-8

-6

-4

-2

0

NT wheat-fallow

OnSurface

NT wheat-corn-millet-fallow

Soil Carbon SequestrationSoil-profile distribution of soil organic C

Soil Organic Carbon (g . kg-1)

0 5 10 15 20 25 30

-0.5

0.0

-0.5

0.0

ApplingLS, LfS, SL, fSL

CecilSL, fSL

Soi

l Dep

th (m

)

-0.5

0.0

DavidsonCL

-0.5

0.0

GreenvillefSL, SCL

-1.0

-0.5

0.0

GrenadaSi, SiL

0 5 10 15 20 25 30 35

HoustonC

LakelandLS, LfS, S, fS

NorfolkLS, LfS, SL, fSL

RustonLS, LfS, fSL,SL, fLS, SiL

SharkeyC

GrassCropForest

From Franzluebbers (2005) Soil Till. Res. 83:120-147 with data from McCracken (1959)

The vast majority of soils in the southeastern USA and elsewhere have very low concentration of soil organic C below the surface 0.5 m

Therefore there is a justified focus on measuring soil organic C in surface soil

Soil Carbon Sequestration

Soil Organic Carbon (g . kg-1)0 10 20 30 40 50 60

SoilDepth(cm)

-30

-20

-10

0

4-yr conventional tillage

Management Systems at Watkinsville GA

16-yr conservation tillage4-yr conventional tillage

Management Systems at Watkinsville GA

15-yr tall fescue pasture16-yr conservation tillage4-yr conventional tillage

Management Systems at Watkinsville GA

Depth distribution of soil organic C

From Schnabel et al. (2001) Ch. 12, Pot. U.S. Grazing Lands Sequester C, Lewis Publ.

Bulk Density(Mg . m-3)

1.2 1.4 1.6

*

*

Soil Carbon Sequestration

Data from Franzluebbers et al. (1999)Soil Sci. Soc. Am. J. 63:349-355

Soil Organic C(g . kg-1)

0 5 10 15 20

SoilDepth(cm)

-15

-10

-5

0*

Disk tillageNo tillage

3.3 * 5.9

7.5 7.4

10.3 8.9

Soil (0-15 cm)Soil + residue

21.1 22.221.2 * 26.5

Carbon Content(Mg . ha-1)

DT NT 0.1 * 4.3

Depth distribution of soil organic C

Replicated experimentGeorgia – SCLTypic Kanhapludult4-yr studySorghum, soybean, cotton

Soil Carbon SequestrationSoil-profile distribution of soil organic C

Data from Gal et al. (2007) Soil Till. Res. 96:42-51

Replicated experimentIndiana – SiCLTypic Haplaquoll28-yr studyCorn and corn/soybean

0.620.810.44

0.38

0.36

0.32

CumulativeCarbon

SequestrationRate

(Mg/ha/yr)

SoilOrganic C

(g . kg-1)0 10 20 30

SoilDepth(cm)

-100

-80

-60

-40

-20

0

BulkDensity(Mg . m-3)

1.2 1.4 1.6

Carbon Content(Mg . ha-1)

PT NT 13.6 << 22.5

43.9 > 33.3

12.8 12.2

Soil (0-100 cm) 159.2 < 169.3

***

Plow tillageNo tillage

*

*

******27.9 << 36.442.8 < 48.2

18.2 16.7

Soil (0-30 cm) 84.1 < 107.0

Soil Carbon SequestrationSoil-profile distribution of soil organic C

SoilOrganic C

(g . kg-1)0 10 20 30

SoilDepth(cm)

-60

-40

-20

0

BulkDensity(Mg . m-3)

1.2 1.4 1.6

Carbon Content(Mg . ha-1)

PT NT 10.1 11.9

41.2 41.6

9.0 7.2Soil (0-10 cm) 19.7 < 27.0

Plow tillageNo tillage

9.5 < 15.0

30.7 24.2

Soil (0-60 cm) 100.6 100.0

*

Field survey – KY, OH, PA11 different soilsAlfisols, Ultisols, Inceptisols13 + 7 years of tillage systemCorn, soybean, alfalfa, vegetables

Data from Blanco and Lal (2008)Soil Sci. Soc. Am. J. 72:693-701

0.56

0.60

0.09

-0.05

0.14

CumulativeCarbon

SequestrationRate

(Mg/ha/yr)

Soil Organic Carbon Sequestration (Mg . ha-1 . yr-1)-1.0 -0.5 0.0 0.5 1.0

SoilDepth(cm)

-20

-15

-10

-5

0

Difference in SOC betweenconservation tillage and

conventional tillage(SOC cons - SOC conv) / years

On-farm surveyfrom 29 locations

in southeastern USA

Soil Carbon Sequestration

*

Data from Causarano et al. (2008)Soil Sci. Soc. Am. J. 72:221-230

Calculation by relative difference

Field survey – AL, GA, SC, NC, VAUltisols, Alfisols, Inceptisols12 + 6 years of conservation tillageCotton, corn, soybean, peanut

Sequestration of SOC

(Mg ha-1 yr-1)--------------------

0.41

0-20 cm 0.45 *

0.08

-0.03

Soil Carbon Sequestration

Soil Organic Carbon Sequestration (Mg . ha-1 . yr-1)-1.0 -0.5 0.0 0.5 1.0

SoilDepth(cm)

-20

-15

-10

-5

0

Difference in SOC betweenperennial pasture andconventional tillage

(SOC cons - SOC conv) / years

On-farm surveyfrom 29 locations

in southeastern USA

Data from Causarano et al. (2008)Soil Sci. Soc. Am. J. 72:221-230

*

*

Calculation by relative difference

Field survey – AL, GA, SC, NC, VAUltisols, Alfisols, Inceptisols12 + 6 years of conservation tillageCotton, corn, soybean, peanut

Sequestration of SOC

(Mg ha-1 yr-1)--------------------

0.53

0-20 cm 0.74 *

0.17

0.05

0.15Mg C/ha/yr

0.00Mg C/ha/yr

Difference0.15

Mg C/ha/yr

0.15Mg C/ha/yr

-0.10Mg C/ha/yr

Difference0.25

Mg C/ha/yr

Soil Carbon SequestrationCalculation by change with time

Years of Management0 25 50 75

SoilOrganicCarbon

(Mg . ha-1)

0

10

20

30

40

Conventionalagriculturefollowing

permanent cover

Conservationagriculture

Scenario A

Years of Management0 25 50 75

SoilOrganicCarbon

(Mg . ha-1)

0

10

20

30

40

Conventionalagriculturefollowing

permanent cover

Conservationagriculture

Scenario A

0 25 50 75

Scenario B

Conventionalagriculture

for long history

Years of Management0 25 50 75

SoilOrganicCarbon

(Mg . ha-1)

0

10

20

30

40

Conventionalagriculturefollowing

permanent cover

Conservationagriculture

Scenario A

0 25 50 75

Scenario B

0 25 50 75 100

Scenario C

Conventionalagriculture

for long history

Conventionaltillage

with adoption ofother best

managementpractices

0.15Mg C/ha/yr

0.10Mg C/ha/yr

Difference0.05

Mg C/ha/yr

Temporal and comparative approaches of value; in combination best!

Example of short-term change

Franzluebbers and Stuedemann (2008) Soil Sci. Soc. Am. J. 72:613-625

Soil Organic C (g . kg-1)0 10 20 30 40

SoilDepth(cm)

-20

-10

0

Initiation

-30

-20

-10

0

At end of 3 years

Conventional tillageNo tillage

Starting from long-term pasture condition

Soil Carbon Sequestration

Years of Management0 1 2 3

0-12 cm

CT vs NT ***

Years of Management0 1 2 3 4

0-20 cm

CT vs NT **

0 1 2 3

TotalOrganicCarbon

(Mg . ha-1)

0

10

20

30

40

50

Years of Management

0-6 cm

CT vs NT ***

PastureNo tillage (NT)Conventional tillage (CT)

Franzluebbers and Stuedemann (2008) Soil Sci. Soc. Am. J. 72:613-625

∆ SOC = −1.54 Mg/ha/yr

∆ SOC = 0.19 Mg/ha/yr

∆ SOC = 1.15 Mg/ha/yr

Soil Carbon SequestrationExample of temporal and comparative combination

Soil Carbon Sequestration

Franzluebbers et al. (2001) Soil Sci. Soc. Am. J. 65:834-841 and unpublished data

Years of Management0 1 2 3 4 5 6 7 8

SoilOrganicCarbon

(Mg . ha-1)

12

14

16

18

20

22

24

Cut for hay

Years of Management0 1 2 3 4 5 6 7 8

SoilOrganicCarbon

(Mg . ha-1)

12

14

16

18

20

22

24

Cut for hay

Unharvested

Years of Management0 1 2 3 4 5 6 7 8

SoilOrganicCarbon

(Mg . ha-1)

12

14

16

18

20

22

24

Unharvested

Cut for hay

Lowgrazing pressure

Years of Management0 1 2 3 4 5 6 7 8

SoilOrganicCarbon

(Mg . ha-1)

12

14

16

18

20

22

24

Unharvested

Cut for hay

Lowgrazing pressure

Highgrazing

pressure

Establishment of bermudagrass pasture following long-term cropping in Georgia USA (16 °C, 1250 mm)

Soil C sequestration(Mg ha-1 yr-1) (0-5 yr):--------------------------------Hayed 0.30Unharvested 0.65Grazed 1.40

Example of temporal and comparative approaches

Modeling of regional farming systems

Abrahamson et al. (2007) J. Soil Water Conserv. 62:94-102

Soil Conditioning Index-1.5 -1.0 -0.5 0.0 0.5 1.0

Change inSoil Organic CSimulated by

EPIC(Mg . ha-1 . yr-1)

0.0

0.2

0.4

0.6

0.8

1.0

Cotton - CTCotton/wheat - NTCorn/wheat - cotton/wheat - NTBermudagrass - corn/wheat - cotton/wheat - NT

SOC = 0.06 + 0.018*exp(5.90*SCI), r2 = 0.69SCI a simple, useful tool that could be used to design appropriate farming systems to maximize C sequestration in Georgia

Soil Carbon Sequestration

Soil Carbon SequestrationIn the USA and Canada, conservation-tillage cropping can sequester

an average of 0.33 Mg C/ha/yr

Data from Franzluebbers and Follett (2005) Soil Tillage Res. 83:1-8

Cold-dry region(6 °C, 400 mm)

0.27 + 0.19 Mg C/ha/yr

Northwest

Hot-dry region(18 °C, 265 mm)

0.30 + 0.21 Mg C/ha/yr

Southwest

Hot-wet region(20 °C, 1325 mm)

0.42 + 0.46 Mg C/ha/yr

Southeast

Cold-wet region(6 °C, 925 mm)

−0.07 + 0.27 Mg C/ha/yrNortheast

Mild region(12 °C, 930 mm)

0.48 + 0.59 Mg C/ha/yr

Central

No tillage needs high-residue producing cropping system to be effective

Soil Carbon Sequestration

Soil Organic Carbon Sequestrationin the Southeastern USA

----------------------------------------------------

0.28 + 0.44 Mg C/ha/yr(without cover cropping)

0.53 + 0.45 Mg C/ha/yr(with cover cropping)

Franzluebbers (2005) Soil Tillage Res. 83:120-147.

Photos of 2 no-tillage systems in Virginia USA

Since animal manure contains 40-60% carbon, its application to land should promote soil organic C sequestration

Conversion of C in poultry litter to soil organic C was 10 + 19%

Note: Manure application transfers C from one land to another Franzluebbers (2005) Soil Tillage Res. 83:120-147

Franzluebbers (unpublished data)

In a 12-year experiment on bermudagrass / tall fescue, soil organic C sequestration due to poultry litter application was 0.24 + 0.47 Mg C/ha/yr

Soil Carbon SequestrationInfluence of animal manure application

Temperate or frigid regions (23 + 15%)

Thermic regions (7 + 5%)

Moist regions (8 + 4%)

Dry regions (11 + 14%)

Percentage of carbon applied as manure retained in soil(review of literature in 2001)

Soil Carbon SequestrationInfluence of animal manure dependent on climate

Opportunities exist to capture more carbon from crop and grazingsystems when the two systems are integrated:

Soil Carbon Sequestration

Utilization of ligno-cellulosic plant materials by ruminantsManure deposition directly on landWeeds can be managed with management rather than chemicals

Integration of crops and livestock

Franzluebbers and Stuedemann (2008)Soil Sci. Soc. Am. J. 72:613-625

Influence of pasture establishment

Data from Wright et al. (2004) Soil Biol. Biochem. 36:1809-1816and Franzluebbers et al. (2000) Soil Biol. Biochem. 32:469-478

SOC (Mg ha-1 yr-1) 10 yrs 25 yrs 50 yrsHayed BG (GA) 0.29 0.21 0.13Grazed BG (TX)Grazed TF (GA)

SOC (Mg ha-1 yr-1) 10 yrs 25 yrs 50 yrsHayed BG (GA) 0.29 0.21 0.13Grazed BG (TX) 0.50 0.33 0.19Grazed TF (GA)

SOC (Mg ha-1 yr-1) 10 yrs 25 yrs 50 yrsHayed BG (GA) 0.29 0.21 0.13Grazed BG (TX) 0.50 0.33 0.19Grazed TF (GA) 0.91 0.55 0.31

Years of Management0 10 20 30 40

SoilOrganicCarbon

(g . kg-1)0-15 cm

0

2

4

6

8

10

12

From a long-term bermudagrass grazing study in Texas (Rouquette)

Stand Age of Grass (years)0 10 20 30 40 50

SoilOrganicCarbon

(Mg . ha-1)

0

10

20

30

40

50'K-31' Tall fescue

'Coastal' bermudagrass

[0-20 cm depth] Georgia

Years of Management0 10 20 30 40 50

MaximumSoil Organic CAccumulation

(%)

0

20

40

60

80

100

Soil Carbon Sequestration

Franzluebbers (2005) Soil Tillage Res. 83:120-147

Nitrogen Fertilization (kg . ha-1 . yr-1)0 100 200 300

Changein

SoilOrganicCarbon

(Mg . ha-1 . yr-1)

0.0

0.4

0.8

1.2

1.6

Conventional Tillage

Nitrogen Fertilization (kg . ha-1 . yr-1)0 100 200 300

Changein

SoilOrganicCarbon

(Mg . ha-1 . yr-1)

0.0

0.4

0.8

1.2

1.6

Conventional Tillage

No Tillage

Nitrogen Fertilization (kg . ha-1 . yr-1)0 100 200 300

Changein

SoilOrganicCarbon

(Mg . ha-1 . yr-1)

0.0

0.4

0.8

1.2

1.6

Conventional Tillage

No Tillage

Carbon cost ofN fertilizer

(0.98 to 2.82 kg C . kg-1 N)

Nitrogen Fertilization (kg . ha-1 . yr-1)0 100 200 300

Changein

SoilOrganicCarbon

(Mg . ha-1 . yr-1)

0.0

0.4

0.8

1.2

1.6

Conventional Tillage

No Tillage

Carbon cost ofN fertilizer

(0.98 to 2.82 kg C . kg-1 N)

Therefore, soil carbon sequestration needs to be evaluated with a system-wide approach that includes all costs and benefits

For those of us working on greenhouse gas issues, this provides us with a formidable challenge

Soil Carbon SequestrationNitrogen fertilization effect

1 kg N2O-N ha-1 = 127 kg C ha-1

Nitrous Oxide EmissionReview of recent research

Total of 12 papers in a special Issue “N2O Emissions from Agricultural Soils in Canada”Can. J. Soil Sci. Volume 88, No. 2, April 2008

Tillage effects on N2O emission from soils under corn and soybeans in eastern Canada, Gregorich, Rochette, St-Georges, McKim, Chan

Nitrous oxide and carbon dioxide emissions from monoculture and rotational cropping of corn, soybean and winter wheat, Drury, Yang, Reynolds, McLaughlin

Effect of fertilizer nitrogen management on N2O emissions in commercial corn fields, Zebarth, Rochette, Burton, Price

Nitrous oxide, carbon dioxide and methane emissions from irrigatedcropping systems as influenced by legumes, manure and fertilizer, Ellert, Janzen

Spring thaw and growing season N2O emissions from a field planted with edible peas and a cover crop, Pattey, Blackburn, Strachan, Desjardins, Dow

Nitrous Oxide EmissionInfluence of cropping

Drury et al. (2008) Can. J. Soil Sci. 88:163-174

Woodslee ONBrookston clay loamIn Years 2, 3, and 4Fertilizer – 170 kg N/ha corn,83 kg N/ha wheat, none for soybean

Crop rotationCrop

Corn Soybean WheatMonoculture 2.62 + 1.82 0.84 + 0.52 0.51 + 0.15

Emission (kg N2O-N ha-1)

Corn/soybean 1.34 + 0.52 0.70 + 0.43 –

Corn/soybean/wheat 1.64 + 0.76 0.73 + 0.24 0.72 + 0.33

Importance of (1) N fertilizer rate, (2) type and amount of residue from previous crop, and (3) residual N.

Nitrous Oxide EmissionInfluence of season, crop, and tillage

Gregorich et al. (2008) Can. J. Soil Sci. 88:153-161

Ottawa ONLoam soilCorn-wheat-soybean rotationIn Years 9, 10, and 11Fertilizer (112 kg N/ha) corn only

N2OEmission

(kg N . ha-1)

0.0

0.5

1.0

1.5

2.0

2.5

Apr-May Aug-SepJun-Jul

n=224

n=400

n=176

0.0

0.5

1.0

1.5

2.0

2.5

Corn Soybean

Plow tillageNo tillage

Importance of soil nitrate from fertilizer

Nitrous Oxide EmissionInfluence of residues, tillage, and fertilizer

Gregorich et al. (2005) Soil Till. Res. 83:53-72

Condition

Annual crops / fall

incorporation

Annual crops / not

incorporated

Perennial crops / not

incorporatedWinter/spring (n= 6-10) 2.41 + 1.79 1.19 + 0.79 0.29 + 0.39

Emission (kg N2O-N ha-1)

Condition Moldboard plow No tillageTillage (n=15) 1.60 + 3.16 1.96 + 4.66

Condition − N fertilizer + N fertilizerAnnual crops (n=14-57) 1.53 + 1.00 2.82 + 2.78Perennial crops (n=6-9) 0.16 + 0.21 0.62 + 1.10

Nitrous Oxide EmissionInteraction of tillage with soil type

Rochette (2008) Soil Till. Res. 101:97-100

Soil Aeration

N2OEmission

(kg N . ha-1)

0

1

2

3

4

5

6

7

8

Good Medium

Conventional tillageNo tillage

Poor

p = 0.06

45 site-years of data reviewedBrazil, Canada, France, Japan,New Zealand, United Kingdom, USA

Nitrous Oxide EmissionInfluence of N fertilizer

Gregorich et al. (2005) Soil Till. Res. 83:53-72

1.19% of applied fertilizer N emitted as N2O

Compared favorably with the IPCC coefficient of 1.25%

Note the high variation in data despite the close comparison

Franzluebbers and Brock (2007)Soil Till. Res. 93:126-137

Response0-20-cm depth

Silage Crop RemovalInitially 0.5 yr-1 1-2 yr-1

At end of 7 years

Bulk density (Mg m-3) 1.43 1.37 ns 1.39

Macroaggregate stability (g g-1) 0.74 0.87 * 0.81

Soil organic C (mg g-1) 11.7 14.3 * 12.5

Soil Carbon SequestrationInfluence of crop residue removal

On-farm researchNorth Carolina PiedmontCorn silage each year vs corn silage less often

Reduced water infiltration, especially with >50% removal

Increased soil erosion, most likely with >50% removal

Reduced soil organic C and N storage (dependent upon soils, climate, etc.)

Soil organic matter is a key component that controls many other soil properties

Reduced water storage and increased surface soil temperature

Increased soil strength

Reduced soil aggregation

Reduced soil biological activity

Soil Responses to Crop Residue Removal

Soil Carbon SequestrationSummary

Soil organic carbon can be sequestered with adoption of conservation agricultural practices

Enhanced soil fertility and soil qualityMitigation of greenhouse gas emissionsSoil surface change is most notableLong-term changes are most scientifically defensible

Soil Carbon SequestrationAcknowledgements

FundingAgricultural Research Service

(ARS)US-Department of EnergyMadison County Cattleman’s

AssociationUSDA-National Research

Initiative – Soil ProcessesCotton IncorporatedGeorgia Commodity

Commission for CornThe Organic CenterARS GRACEnet team