Soil Carbon: Reservoir for a Resilient Agriculture · Alan Franzluebbers. Ecologist, Raleigh NC. Soil Carbon: Reservoir for a Resilient Agriculture

Alan FranzluebbersEcologist, Raleigh NC

Soil Carbon: Reservoir for a

Resilient Agriculture

From Population Reference Bureau (2006) www.prb.org

A.D.2000

A.D.1000

A.D.1

1000B.C.

2000B.C.

3000B.C.

4000B.C.

5000B.C.

6000B.C.

7000B.C.

1+ million years

8

7

6

5

2

1

4

3

OldStone

Age New Stone AgeBronze

AgeIronAge

MiddleAges

ModernAge

Black Death — The Plague

9

10

11

12

A.D.3000

A.D.4000

A.D.5000

1800

1900

1950

1975

2000

2100

Future

WorldPopulation(billions)

7.5 billionMay 2017

Consider human population

From Tilman et al. (2002) Nature 418:671-677

1021 g (zettagrams - Zg)

Cereal production↑ 2.6 times

Global agriculture’s response

From Tilman et al. (2002) Nature 418:671-677

Phosphorus↑ 2.8 times

Nitrogen↑ 10.9 times Water

↑ 2.2 times

Global agriculture’s response

Continued deployment of traditional industrial practices is not sustainable for the soil resource base

Our collective actions have

grave consequences

Converting suitable agricultural lands to nature may not provide us enough…

Production Environment

Management

How to balance greater productivity with improved environmental quality?

Soil

Atmosphere

Hydrosphere

BiosphereLithosphere

Ecosystem services

Supporting ServicesEssential to other services, including biomass production,

production of atmospheric oxygen, soil formation and retention,nutrient cycling, water cycling, and provisioning of habitat

Regulating ServicesBenefits obtained from

regulation of ecosystemprocesses, including

climate,water,

human diseases

Provisioning ServicesProducts obtained

from ecosystems, includinggenetic resources,

food, feed, fiber, fuel,fresh water

Cultural ServicesNon-material benefits

obtained throughcognitive development,aesthetic experience,spiritual enrichment,

recreation,reflection

From Millennium Ecosystem Assessment (2005)

Human relationship with the environment

A simple analogy

Provisioning services

Regulatingservices

Cultural services

…an ideal situation

http://www.fishriver.net/river/red_river1.jpg

Supporting services

Human relationship with soil

Soil Management

…the harsh reality

Nutrientcycling

Soilformation

Primaryproduction Food Fresh

water

Woodand fiber

Fuel

Climatecontrol

Floodcontrol

Diseasecontrol

Waterpurification

Aesthetics

Spiritual

Educational

Recreational

Soil organic matter is important as an indicator of ecosystem services

ProductivitySoil

OrganicMatter

Water relations BiodiversityNutrient cycling

Greenhouse gasmitigation

What is soil carbon?The most abundant constituent of soil organic matter [i.e. 58% of SOM as carbon]

As part of carbonate minerals [e.g. CaCO3]

Living components – plant biomass, faunal biomass, microbial biomass

Non- living components – Particulate organic matter [litter, macroorganic matter, light

fraction] Dissolved organic matter [<0.45 μm] Humus [non-humic biomolecules (e.g. discrete biopolymers

of sugars, proteins, fats, lignin, etc.), humic substances (humic acid, fulvic acid, humin)]

Inert organic matter [charcoal, graphite, coal]

Why is soil organic carbon important?A vital component of ecosystem properties, processes, and functions

Physical:1. Color

Dark color of organic matter alters thermal properties

2. Low solubility Ensures that organic matter inputs are retained and not rapidly

leached from the soil profile

3. Water retention Directly helps to absorb several times its mass of water

Indirectly retains water through effect on pore geometry and soil structure

4. Stabilization of soil structure Binding of mineral particles to form water-stable aggregates

Example: Effect of organic matter on water-related properties

Soil Organic C (g . kg-1)35 40 45 50

Mean-WeightDiameter of

Water-StableAggregates

(mm)

1.0

1.5

2.0

2.5

MWD = -1.1 + 0.07 (SOC)r2 = 0.70

Mollic Cryoboralfs in Alberta Canada

Soil Organic C (g . kg-1)0 5 10 15

WaterInfiltration(mm . hr-1)

0

5

10

15Typic Kanhapludults in Georgia

Inf = -4.2 + 1.42 (SOC)r2 = 0.74

Data from Arshad et al. (2004) Soil Till. Res. 77:15-23Carreker et al. (1977) USDA-ARS S-160

Soil organic matter improves surface

conditions to get more water into soil

Sand

Soil Organic Matter (%)

SoilWater

Content(vol %)

Example: Effect of organic matter on soil water storage

From Hudson (1994) J. Soil Water Conserv. 49:189-194

Permanent wilting point

Field capacity Silt Loam

Sand – FLSilt Loam – IA, WI, MN, KSSurface soils only

2-4 times greater water storage in

surface soil possible

Availablewater

Availablewater

At 1% OM12.9% water

At 5% OM27.7% water

Why is soil organic carbon important?

A vital component of ecosystem properties, processes, and functions

Chemical:1. Cation exchange capacity

High charge enhances retention of Al, Fe, Ca, Mg, NH4, etc.

2. Buffering capacity and pH effects Avoids large swings in pH to keep in more acceptable range for

plants

3. Chelation of metals Complexation with metals to enhance dissolution of minerals,

enhance availability of P, reduce losses of micronutrients, and reduce toxicity

4. Interactions with xenobiotics Alter biodegradability, activity, and persistence of pesticides

Example: Effect of organic matter on soil cations

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

Meh

lich-

I Ext

ract

able

Cal

cium

(mg

kg-1

)

0

100

200

300

400

500Ca = 40 + 4.7 (SOC)r2 = 0.29

Unpublished data (Franzluebbers and Haney)

Analysis of 420 samples (0-6 cm depth) from a 20-ha field near Watkinsville GA

Why is soil organic carbon important?

A vital component of ecosystem properties, processes, and functions

Biological:1. Reservoir of metabolic energy

Energy embedded in organic molecules to drive biological processes

2. Source of macronutrients Mineralization of organic matter releases N, P, S, and other

elements

3. Enzymatic activities Both enhancement and inhibition of enzymes by humic materials

4. Ecosystem resilience Accumulation of SOM can enhance the ability of an ecosystem to

recover from various disturbances

Example: Effect of organic matter on nitrogen mineralization

Flush of CO2-C Following Rewetting of Dried Soil(ug . g-1 . 3 d-1)

0 200 400 600 800 1000

Net

N M

iner

aliz

atio

n(u

g . g-1

. 24

d-1

)

0

50

100

150

b0 = -8b1 = 0.36b11 = 0.00024r2 = 0.72

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

Immobilization can occur with

excessively high carbon

A steady supply of inorganic nitrogen

is available from the decomposition of

easily decomposed organic matter

Provisioning ecosystem serviceSOC related to food, production

From Diaz-Zorita (1999) Agron. J. 91:276-279

Argentine Pampas134 farmer fieldsUdolls, Ustolls, Psamments3 years of wheat yield data0-20 cm depth

Achieving or maintaining

maximum soil organic matter

storage is beneficial to

crop productivity

Regulating ecosystem serviceSOC related to GHG emissions

Carbon dioxide (CO2)

Storage of carbon in soilreduces net CO2 emission

to the atmosphere

Methane (CH4)

Soils with high surface soilorganic matter are often

a net sink for CH4;but excessively wet soils

will emit CH4

Nitrous oxide (N2O)

Water-soluble organic C,nitrate (NO3), and low oxygen areprerequisites for denitrification

Cultural ecosystem serviceSOC related to spirituality / aesthetics

http://www.ers.usda.gov/amberwaves/September04/images/soil-erosion5.jpg

Land clearing and degradation

Supporting ecosystem serviceSOC related to formation and land preservation

Quantifying soil organic carbon inagricultural systems

Crop Residue Addition (Mg . ha -1 . yr-1)0 5 10 15 20

SoilOrganicCarbon(g . kg-1)

10

15

20

25

Alfalfa residueCorn residue

Initial soil organic C level

Data from Larson et al. (1972) Agron. J. 64:204-208

IowaMarshall SiCLTypic Hapludoll11-yr studyPlow tillage

SOC response to residue input

s

Steady-state level needed to maintain SOC

Franzluebbers et al. (1998) Soil Till. Res. 47:303-308

Texas10-yr studyRotations and tillageF.M. Hons (P.I.)

0.3 0.4 0.5 0.6 0.7 0.8 0.9

EstimatedCarbonInput

(Mg . ha-1 . yr-1)

0

2

4

6

8

10

Conventional Tillage

No Tillage

Cropping Intensity(fraction of year that a crop is in the field)

Soybean

Sorghum

WheatSorghum -

wheat / soybeanWheat /soybean

Cropping intensity

Franzluebbers et al. (1998) Soil Till. Res. 47:303-308

0.3 0.4 0.5 0.6 0.7 0.8 0.9

SoilOrganicCarbon

Sequestration(g SOC . g-1 C input)

0.00

0.05

0.10

0.15

0.20

0.25

Conventional Tillage

No Tillage

Cropping Intensity (fraction of year)

SOY SOR WHT ROT W/S

TexasWeswood SiCLUstic Udifluvent10-yr studyDifferent rotations

SOC response to C inputs

Relative Environmental Conditions(fraction of optimum)

0.0 0.2 0.4 0.6 0.8 1.0

RelativeProduction

0.0

0.2

0.4

0.6

0.8

1.0

e.g. temperature and moisture


0.0 0.2 0.4 0.6 0.8 1.0

RelativeProduction

0.0

0.2

0.4

0.6

0.8

1.0

RelativeDecomposition

Diversity of environmental conditions exist around the world

e.g. temperature and moisture


0.0 0.2 0.4 0.6 0.8 1.0

RelativeProduction

0.0

0.2

0.4

0.6

0.8

1.0

RelativeDecomposition

Relative Carbon

Sequestration

Diversity of environmental conditions exist around the world

On a local scale, organic C distribution in the soil matters

Franzluebbers (2002) Soil Till. Res. 66:197-205

Surface residue

“Plow layer” of soil

Zone most affected by

management

Zone relatively

unaffected by

management

Stratification Ratio

SOC (0-5 cm).____________.

SOC (15-30 cm)

0-5 cm

15-30 cm Plowed soils tend to have values near 1

Why calculate stratification ratio of SOC?

Soils differ in inherent stocks of organic CBasic soil properties and

processes can be isolated at appropriate depths for their response to managementLong-term outcomes can be

predicted from shorter term studiesComparative analyses of

conservation tools across soils would benefit technology transfer and adoption

Some origins…

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

SoilDepth(cm)

-12

-9

-6

-3

0

Conventional tillageNo tillage

Quantity of SOC(Mg . ha-1)0-12 cm

-------------------9.4

18.9

NT / CT 2.0 4.1

Franzluebbers (2002) Soil Till. Res. 66:197-205

Distributionof SOC

(0-3 / 6-12 cm)-------------------

1.45.7

Effect of SOC stock vs depth distribution on infiltration

CT undisturbed

NT undisturbed

Time (minutes)for 2.8 cm of waterto infiltrate surface---------------------------

CT NT2x quantitySieved 10.2 7.3

P = 0.10(28% reduction in time)

4x distributionIntact 12.9 3.4

P < 0.01(74% reduction in time)

Greater rate of infiltration due to depth distribution of SOC rather

than stock of SOCFranzluebbers (2002) Soil Till. Res. 66:197-205

Implications of stratified SOC for land managers

Easier to change SOC at the surface than to change SOC deeper in the profileGreater impact from increment of change in SOCCost per unit of effective change in SOC is reducedIncreasing SOC is not easy in some environments,

so faster and more effective change in SOC maximizes benefits to farmers and to society (i.e. cleaner environment)

Prediction of soil organic C sequestration from stratification ratio

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

Stratification Ratio of Soil Organic C(0-5 cm / 12.5-20 cm)

0 1 2 3 4 5 6 7 8

SoilOrganicCarbon

(Mg . ha-1)[0-20 cm]

0

10

20

30

40

50

60

Conservation-tillage croplandConventional-tillage cropland

Pasture

SOC = 40.0 (1 - e-0.53 SR)r2 = 0.34

StratificationRatio of

SOC------------------

4.2 + 1.5

2.7 + 0.8

1.4 + 0.3

Surface soil condition is important for water quality

Surface Crop Residue (Mg . ha-1)0 2 4 6 8 10

Fractionof

Rainfallas

Runoff

0.0

0.2

0.4

0.6

0.8

1.0Well-drained silt loam soil in IndianaWheat straw applied to bare ground156 mm of rainfall simulated during 3 days


Fractionof

Rainfallas

Runoff

0.0

0.2

0.4

0.6

0.8

1.0


Soil Loss

(Mg . ha-1)

0

6

12

18

24

30Well-drained silt loam soil in IndianaWheat straw applied to bare ground156 mm of rainfall simulated during 3 days

Data from Mannering and Meyer (1963) Soil Sci. Soc. Am. Proc. 27:84-86

Surface cover is important for

controlling runoff and soil erosion

Literature review on land use and surface soil condition

Pennsylvania

Virginia

Ohio

Kentucky

Wisconsin

Georgia

Alabama

Mississippi

Oklahoma

Texas

Sharpley and Kleinman (2003)

Ross et al. (2001)Van Doren et al.

(1984); Shipitaloand Edwards (1998)

Blevins et al. (1990); Seta et al. (1992)

Andraski et al. (1985)

Langdale et al. (1985); Endale et al. (2000, 2001, 2004); Potter et al. (2004); Bosch et al. (2005)

Truman et al. (2003)

Rhoton et al. (2002)Sharpley and

Smith (1994)Harmel et al. (2004)

Summarized in Franzluebbers (2008) J. Integr. Biosci. 6:15-29

Water runoff impacts


WaterRunoff(% of

precipitation)

0

10

20

30

40

n = 15 n = 15 n = 2

a

b b

ConventionalTillage

Cropping

NoTillage

Cropping

PerennialPasture

Assumed Stratification Ratio of SOC1.5 3.0 4.5

Soil loss impacts



SoilLoss

(Mg . ha-1)

0

2

4

6

8

n = 14n = 14

n = 3

a

b b

ConventionalTillage

Cropping

NoTillage

Cropping

PerennialPasture

Nitrogen loss impacts



Loss ofNitrogenin Runoff(kg . ha-1)

0

5

10

15

20

n = 3

a

b

c

ConventionalTillage

Cropping

NoTillage

Cropping

PerennialPasture

n = 5n = 6

Total

Dissolved

Phosphorus loss impacts



Loss ofPhosphorus

in Runoff(kg . ha-1)

0

1

2

3

n = 3

a

b

c

ConventionalTillage

Cropping

NoTillage

Cropping

PerennialPasture

n = 5n = 6

Total

Dissolved

Stratification of SOC

Quantity of soil organic carbon (SOC) is important to ecosystem functioning

However, the distribution of SOC (at the surface) is even more important

Soil health and ecosystem functioning are closely associated with stratification ratio of SOC

Empirical data are becoming more available to suggest that depth distribution of SOC as affected by long-term management can be used as a signature of soil health

Management to promote soil carbon

Plant and animal residuesTiming

Placement

Quantity

Quality

Minimalsoil

disturbancePermanent cover

& diversity

No tillage, minimum tillage, ridge tillage

Cover cropping, rotation Integrated crop-livestock

systems

Quantity Quality Diversity Timing

Why important? Source of energy Temperature and

moisture moderation

Maintain surface residues

Data from multiple sourcesReported in Franzluebbers (2005) Soil Till. Res. 83:120-147

Time needed for conservation systems to mature

Franzluebbers and Stuedemann (2010) Soil Sci. Soc. Am. J. 74:2131-2141

Soil Organic Carbon Sequestration (kg . ha-1 . yr-1)0 200 400 600 800 1000

TotalSoil

NitrogenAccumulation(kg . ha-1 . yr-1)

0

20

40

60

80

100TSN = 5.7 + 0.102 (SOC)r2 = 0.98

An investment for the future…

Franzluebbers and Stuedemann (2010) Soil Sci. Soc. Am. J. 74: 2131-2141

YearlyAccumulation

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

0.620.59

0.32

0.07

Years of Management0 2 4 6 8 10 12

SoilOrganicCarbon

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

10

15

20

25

Cut for hay

Unharvested

LowGrazing Pressure

(High Forage Mass)High

Grazing Pressure(Low Forage Mass)

LSD0.05

— Forage harvest effect – Georgia USA

Management effect on soil organic C

Data from Franzluebbers et al. (2001) Soil Sci. Soc. Am. J. 65:834-841

Cattle Stocking Rate (Mg . ha-1 . yr-1)0 1 2 3 4

SoilOrganicCarbon

(Mg . ha-1)[0-20 cm]

34

36

38

40

42

44

LSD0.05

(Hayed)

Bermudagrasspasture grazed by 0, 5.8, and 8.7 steers/ha from May-Sep for 5 yrs

Moderate grazing can stimulate SOC sequestration,

but overgrazing will cause loss of SOC

Implications:Land can be managed for

agricultural production and still preserve environmental

quality…


Data from Studdert et al. (1997) Soil Sci. Soc. Am. J. 61:1466-1472

Year1975 1980 1985 1990 1995


25

30

35

40

Continuous croppingPasturetermination

Year1975 1980 1985 1990 1995


25

30

35

40


6-yr crop2-yr pasture

Pasturetermination

Pasture

Year1975 1980 1985 1990 1995


25

30

35

40



Pasturetermination

Pasture


Pasture

— Crop rotation effects – Argentina


— Diversity of opportunities for integration

Cover crops

Sod rotations

Mixed animal grazing(poultry, browsers, grazers)

Cut-and-carry / manure application

Agroforestry /silvopasture

Neighbor trading

Landscape approaches are needed

Conservation agricultural systems for the future

Sust

aina

bilit

y go

als

Time

+sod

rotations

No tillage

+cover crops

+diverse

rotations

Corn-Wheat/clover-

Cotton/rye-peanut

+agroforestry

and/or silvopasture

+integrated crop-

livestock systems

Conservation agricultural systems for the futureExtending the depth and diversity of roots on individual farms and fields

Conservation agricultural systems for the futureValuing all components of agriculture – balance to achieve sustainability

Biogeochemical

Physical

Chemical

Biological

Key soil health indicators

Summary

Soil is vitally important to many global issues facing society in the coming decadeso Food securityo Climate changeo Clean water and its availabilityo Recycling and nutrient utilization

Soil organic carbon powers many ecosystem serviceso Water and nutrient cyclingo Climate regulationo Food, feed, fiber, and fuel production

Conservation management systems are capable of restoring soil organic carbon for the benefit of societyo Conservation tillage, pastures, cover cropping, manures

“If Earth is the mother of all living things, then soil must be its womb, bearing richness beyond comprehension.

Then too, carbon in soil should be considered the blood energizing the entire body, enabling the Earth to provide a multitude of ecosystem services.”

[email protected]

Documents

Soil Carbon: Reservoir for a Resilient Agriculture · Alan Franzluebbers. Ecologist, Raleigh NC. Soil Carbon: Reservoir for a Resilient Agriculture