Soil Carbon Sequestration fromConservation Agricultural Systems

in Georgia

Alan J. Franzluebbers

Ecologist

Watkinsville GA

Global Concern is in the Air

FromIntergovernmental

Panel onClimate Change

Climate Change Debate

Mary Cleave – NASA (personal communication)

Climate Change Debate

From Intergovernmental Panel on Climate Change

Climate Change Debate

Loehle and McCulloch (2008) Energy and Environment 19:93-100

Managing Carbon Emission

Rising concentration of greenhouse gases has been largely attributed to expanding use of fossil fuels as an energy source, resulting in emission of CO2 to the atmosphere

Reducing net greenhouse gas emission is possible:1. Reduce fossil fuel combustion by becoming more energy

efficient2. Rely more on low-carbon energy sources

• Solar energy capture• Wind power generation• Biomass fuels

3. Carbon sequestration

Terrestrial Carbon Sequestration

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

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

Tillage• Type• Frequency

Fertilization• Rate, timing, placement• Organic amendments

Management Approachesto Sequester Soil Carbon

from Atmosphere to Biosphere

Integrated management• Pest control• Crop / livestock systems

Focus on maximizing carbon input

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

Management Approachesto Sequester Soil Carbon

from Atmosphere to Biosphere

Focus on minimizing carbon loss from soil

Tree plantings

Conservation-tillage cropping

Animal manure application

Improved grassland management

Optimal fertilization

Management Practicesto Sequester Carbon

and Counter Land Degradation

Time (years)0 10 20 30 40 50

BiomassCarbon

Accumulation(Mg . ha-1)

0

20

40

60

80

100

120

140

Pulpwood

Saw timber

Total stand

Advantage of accumulating carbon in perennial biomass is in above- and below-ground growth, as well as in soil organic matter

Tree Plantings

Data from Georgia Forestry Commission (www.gacarbon.org/downloads.aspx)

Conditions:Loblolly pinePiedmont regionCutover forest originExtensive management level

CarbonAccumulation

Rate(Mg/ha/yr)

2.9

2.3

Tree Plantings

Soil organic C accumulation with tree plantings was estimated at 0.12 + 0.11 Mg C/ha/yr

Coarse-root biomass is 20% of total above ground biomass

Post and Kwon (2000) Global Change Biol. 6:317-327

Markewitz (2007) Georgia Carbon Sequestration Registry

www.sppland.com/images/in_pines.jpg

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

Conservation Tillage

In the USA and Canada, no-tillage cropping can sequester an average of 0.33 Mg C/ha/yr

Conservation Tillage

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 (i.e. cover cropping, etc.)

Conservation Tillage

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

Low surface residue cover

High surface residue cover

Some specific examples of research around Georgia

Conservation Tillage

Athens – UGA(Horseshoe Bend)

www.uga.edu/ecology/facilities/horseshoebend/hsb.html

Sorghum / rye croppingCT and NT established in 1978

Hu et al 19950.262113

Hu et al 19971.81152

Hendrix et al 19980.282116

Hu et al 19970.301514

Beare et al 19940.361513

Groffman 19840.40215

Reference∆SOC (NT-CT)(Mg/ha/yr)

Depth (cm)

Years

Some specific examples of research around Georgia

Conservation Tillage

Fort Valley State

Sainju et al 20020.01No

Sainju et al 20020.69Yes

Reference∆SOC (NT-CT)(Mg/ha/yr)

Cover cropping

Tomato croppingCT and NT established in 1994

Evaluation at the end of 5 yrHairy vetch cover crop

Some specific examples of research around Georgia

Conservation Tillage

TiftonGibbs Farm

Potter et al. (2008) J. Environ. Qual. 37:839-847

7.7 + 1.0Conventional

12.4 + 3.4Strip tillage

Soil organic C(0-2 cm depth)

(g/kg)

Tillage

Cotton/rye – peanut/rye croppingRunoff plots established in 1999

Other results from studyWater runoff (Strip Till < Conv Till)Infiltration (Strip Till > Conv Till)

Bosch et al. (2005) Trans. ASAE 48:2137-2144

Watkinsville (USDA-ARS)

Conservation Tillage

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

Watkinsville (USDA-ARS)

Conservation Tillage

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

Years of Management0 1 2 3

SoilOrganicCarbon

(Mg . ha-1)

30

35

40

45

No tillage

Pasture

Conventionaltillage

∆ SOC = -1.54 Mg/ha/yr

∆ SOC = 0.19 Mg/ha/yr

∆ SOC = 1.15 Mg/ha/yr

Regional on-farm survey

Conservation Tillage

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

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

0-20-cm depth0.45 + 0.69 *

Modeling of regional farming systems

Conservation Tillage

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

Animal Manure Application

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

Degradation of permanent grasslands can occur from accelerated soil erosion, compaction, drought, and salinizationStrategies to sequester carbon in soil should improve quality of grasslandsStrategies for restoration should include:

Improved Grassland Management

Enhancing soil coverPlanting species with high forage quality and vigorous regrowthpotentialImproving soil structure to minimize water runoff and soil erosionStocking appropriately to utilize forage, but maintain cover

Improved Grassland Management

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 bermudagrasspasture following long-term cropping in Watkinsville

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

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

Cropland-Grazingland Rotation

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

Years of Management0 1 2 3

SoilOrganicCarbon

(Mg . ha-1)(0-6 cm)

0

5

10

15

20

25

NT-UngrazedNT-Grazed

CT-UngrazedCT-Grazed

LSDp = 0.05

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

Optimal Fertilization

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

Summary and Conclusions

Greenhouse gas concentrations in the atmosphere are increasing and the threat of global change requires our attention

Benefits from conservation agricultural systems can be reaped whether climate change is man-induced or not

A diversity of conservation agricultural management practices can be employed to sequester more carbon in plants and soil

Syntheses of available data are neededGaps in our knowledge need to be researched

Conservation strategies to sequester soil carbon will restore degraded land and avoid further degradation