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Understanding C sequestration. Joel Gruver NCSU Soil Science jgruv@hotmail.com www.soil.ncsu.edu/lockers/Gruver_J/Carbon. Global C cycle. Gt = 10 9 t = Pg = 10 15 g. http://www.grida.no/climate/vital/graphics/large/12.jpg. C fluxes. Relative contributions of major greenhouse gases:.

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Understanding c sequestration
Understanding C sequestration

Joel Gruver

NCSU Soil Science

jgruv@hotmail.com

www.soil.ncsu.edu/lockers/Gruver_J/Carbon


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Global C cycle

Gt = 109 t = Pg = 1015 g

http://www.grida.no/climate/vital/graphics/large/12.jpg



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Relative contributions of major greenhouse gases:

H20 vapor - 36-70%

CO2 – 9-26%

CH4 – 4-9%


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~ 1600 Gt globally

< 5 % of the mass of most soils

C

Mineral particles


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SOM is a complex mixture

Living organisms

Biologically active SOM

Recent residues

Recalcitrant

SOM

Adapted from Magdoff and Weil (2003)


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POM

IOM

DOM

ed

Are these materials components of humus ?

http://www.grdc.com.au/growers/res_summ/pdfs/cso00029.pdf


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  • What is humus ????

  • Humus is organic matter that has been transformed such that its original source is no longer apparent… The diverse products of “humification” have many common characteristics:

  • Extreme chemical complexity

  • Resistance to further decomposition

  • High specific surface and negative charge

  • Dark color


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Organic fractions obtained using classical alkali extraction methods

Most evidence indicates that these fractions are poorly related to soil function

Humic acid

Fulvic acid

Humin


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There is growing evidence that humic substances are aggregated mixtures rather than macromolecules

Does humus have a macromolecular structure ?

hydrophilic

hydrophobic

hydrophilic

hydrophilic

hydrophilic

Piccolo (2002)


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Location within the soil matrix affects SOM dynamics aggregated mixtures rather than macromolecules

Free POM

Sensitivity to management

Intra-aggregate POM

Mineral associated OM

Adapted from Carter (2002)


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SOM aggregated mixtures rather than macromolecules

pools

< 1 year

decades

What is the mean residence time of SOM ??

centuries

Janzen (2006)


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Many studies have shown that physical aggregated mixtures rather than macromoleculesfractions of OM are related to soil function

Sand sized

Silt and clay sized

Particulate OM

Humus

http://www.grdc.com.au/growers/res_summ/pdfs/cso00029.pdf


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Functional impact of SOM fractions aggregated mixtures rather than macromolecules

http://www.grdc.com.au/growers/res_summ/pdfs/cso00029.pdf


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Humus adsorbs ions and molecules aggregated mixtures rather than macromolecules

Adapted from Brady and Weil (2002)


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Humus gives soil a darker color aggregated mixtures rather than macromolecules


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Humus increases plant available H aggregated mixtures rather than macromolecules20

Adapted from Brady and Weil (2002)


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Aggregates form around particulate organic matter ( aggregated mixtures rather than macromoleculesPOM)

Processes that disrupt aggregates accelerate loss of POM


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Some very interesting data… aggregated mixtures rather than macromolecules

Ladd et al. (1993)


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SOM reduces bulk density aggregated mixtures rather than macromolecules

Magdoff and Weil (2004)


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Do not aggregated mixtures rather than macromoleculestill or traffic on wet soils !!!

Structural

damage

Soils with high C

are more resistant to

structural damage !

(Watts and Dexter, 1997)


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Active OM energizes biologically mediated processes aggregated mixtures rather than macromolecules


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The Soil Stomach aggregated mixtures rather than macromolecules

Bacteria

Fungi

Algae

Protozoa

Nematodes

Microarthropods

Enchytraeids

Earthworms

Ants, termites, spiders

Mollusks

Others: rodents, snakes,

voles, amphibians, etc.

Body size increasing

Microflora

Microfauna

Mesofauna

Macrofauna

Megafauna


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The metabolic potential of soil microbial communities greatly exceeds organic inputs to soils


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Why does organic matter accumulate in soils ? greatly exceeds organic inputs to soils


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Blechh !!! greatly exceeds organic inputs to soils

Tastes Bad !!!!

Biochemical recalcitrance

How do you expect to live off this stuff ???

Mineral protection

I can’t get if off, you try !!

Fe

Al

We already are !!!!!!

Yuck !!!!!

Sure is gritty !

Physical protection

There’s gotta to be a way inside !!!

Hey !! There’s good stuff in there !!!!

Adapted from Jastrow and Miller (1997)


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Understanding organic resource quality greatly exceeds organic inputs to soils

(Giller, 2000)


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Relationship between fine mineral fraction and SOM greatly exceeds organic inputs to soils

Magdoff and Weil (2004)


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Relationship between clay content and SOC for 1261 agricultural soils in England and Wales

Webb et al.(2003)


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Microorganisms agricultural soils in England and Wales behave very

differently

in a petri dish

than they do in

soils

http://picturethis.pnl.gov/im2/8208417-5cn0/8208417-5cn.jpg


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Most of the pores where soil microorganisms reside are either environmentally suppressive or lacking in suitable substrates.



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As a result, soil matrix.

most soil microorganisms are in a dormant state

For their prince charmings

to arrive !

waiting…


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Roots soil matrix.

Rain

There are many types of prince charmings !

Tillage

Organic Amendments


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Impact of earthworms on SOM dynamics soil matrix.

Ingested soil

Fresh casts

Aging casts

Soil profile

?

Assimilation Comminution

Nutrient release

Physical protection

(Lavelle and Spain, 2001)


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The priming effect of plant roots soil matrix.

AggregateDisruption

Exposition of organic matter

GrowingRoot

Priming Effect

Exudation

Activation of microorganisms

(Lavelle and Spain, 2001)


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Crop related changes in mineralizable N soil matrix.

No Till

Plow/Disk

Sorghum

Wheat

Soybean

Adapted from Magdoff and Weil (2004)


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Climate affects SOM dynamics soil matrix.

Organic matter

accumulation

Brady and Weil (2002)

70 F


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Landscape position affects SOM dynamics soil matrix.

Poorly drained

Interstream divide

Somewhat poorly drained

Moderately well drained

LANDSCAPE POSITIONS

Well drained

Poorly drained

Interfluve

Shoulder

Valley floor

SOIL DRAINAGE CLASSES

Backslope


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Blackland soils of North Carolina soil matrix.

Lily (1981)



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How much soil matrix.

is enough ??


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Attempting to hoard as much organic matter as possible in the soil, like a miner hoarding gold, is not the correct answer.

Organic matter functions mainly as it is decayed

and destroyed. Its value lies in its dynamic nature.

W. Albrecht, 1938


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Janzen (2006) the soil, like a miner hoarding gold, is not the correct answer.


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There are many ways to “measure” SOM the soil, like a miner hoarding gold, is not the correct answer.

Total organic matter

mass loss by ignition

OM ~ 1.72 x C

Total C

by several methods

Humic matter

alkali extraction

Adapted from Strek and Weber (1985)


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Soil from a long term experiment in Beltsville, MD the soil, like a miner hoarding gold, is not the correct answer.

20 yrs sod,

5 yrs CT

corn

25 yrs

CT corn


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Relatively the soil, like a miner hoarding gold, is not the correct answer.small differences in SOC

Large differences in soil function

After adding water

1.4 % C

140 bu/a

48 bu/a

1.0% C


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Effect of previous 20 years of rotations on SOM and corn growth on Beltsville silt loam in Maryland

Continuous bluegrass sod

Continuous corn with tillage



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NC STATE structure and OM content ! UNIVERSITY

DEPARTMENT of SOIL SCIENCE

Small increases in OM can improve macro-aggregation

Superior air/water relationships

Healthier root growth and function

(justification statement)


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Crop residues structure and OM content !

Cover Crops

Animal manure

Crop residues

20 years of similar tillage intensity

but contrasting levels of organic inputs


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Aggregation changes more rapidly than total C structure and OM content !

Jastrow (1996)


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More OM is needed to stabilize fine textured soils structure and OM content !

16 % clay

39 %

49%

39 %

49%

16 % clay

Adapted from Russell (1973)


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Young particulate organic matter (POM) contributes to disease suppression

Disease Suppression

Damping off

Adapted from Stone et al. (2004)


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Permanganate oxidizable C disease suppression

a routine test for “active” soil C ??



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Crop growth response to no-till planting with a disease suppressionrye cover crop on soils with varying levels of active C

Data suggest little benefit of further increases in active C beyond about 700 mg/kg.

Soils with less than 400 mg/kg usually show large response to increasing SOM.

2.5 g soil in 20 ml 0.02 M KMnO4

From Lucas and Weil


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Managing SOM disease suppression


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A systems approach disease suppression

Well adapted crop

SOM

Nutrient

Management

Water

Management

Adapted from Bailey and Lazarovits (2003)


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well mixed vs. disease suppression

stratified

Conventional tillage

Conservation tillage

Adapted from House and Parmelee (1985)


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Microbial activity in contrasting tillage systems disease suppression

Havlin et al. (1999)


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On-farm sources of OM disease suppression


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Crop disease suppression

residues


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Multi-functional cover crops disease suppression

Cover Crops

Cover crop

Adapted from Magdoff and Weil (2004)


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Innovative cover cropping disease suppression


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Erosion Control Practices disease suppression


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Crop Rotation disease suppression

High residue crops

Cover crops

Forages


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Off-farm sources of OM disease suppression


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Large scale composting disease suppression

pH

Soluble salts

Herbicide residues

Trash

?


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What is the right rate ? disease suppression


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Application rates of slow release organics should diminish over time

Single season N availability = 25%

Tons of compost to supply 150 lbs of N/acre

80

60

Is this graph realistic ?

40

20

3 6 9 12 15 18

Years

Adapted from Magdoff and Weil (2004)


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Nutrient management based on N availability may result in excessive applications of P

Compost = 1.7% N 1.2% P2O5

Cummulative P build up in lbs/acre

3000

Most crops remove 5-10 times as much N as P2O5

> 3000 lbs of excess P when compost is applied at rates based on N

2000

1000

3 6 9 12

YEARS

Adapted from Magdoff and Weil (2004)


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Long term application of organic nutrient sources at rates based on single season availability coefficients is a questionable practice.


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Understanding C sequestration potential based on

Dick and Gregorich (2004)



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Carbon Trading based on

http://www.chicagoclimatex.com/about/faq.html


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An excellent literature review based on

http://www.grdc.com.au/growers/res_summ/pdfs/cso00029.pdf


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Links for some interesting articles related to C sequestrationThe last link is for a very current review (August 2006) of the latest developments in SOM research.

The role of carbon cycle observations and knowledge in carbon management.Annu. Rev. Environ. Resour. 2003. 28:521–58

http://www.soil.ncsu.edu/lockers/Gruver_J/PDF%20files/CcycleObservations.pdf

Simulation of the use of a soil-monitoring network to verify carbon sequestration in soils: will changes in organic carbon stocks be detectable? Communications in Soil Science and Plant Analysis. 2004. 35(17 & 18): 2379–2396

http://www.soil.ncsu.edu/lockers/Gruver_J/PDF%20files/C%20sequestration%20verification.pdf

Estimating active carbon for soil quality assessment: A simplified method for laboratory and field use. American Journal of Alternative Agriculture. 18(1):3-17. 2003.

http://www.soil.ncsu.edu/lockers/Gruver_J/PDF%20files/Permanganatearticle.pdf

Conventional row crop agriculture: putting America’s soils on a white bread diet. Journal of Soil and Water Conservation. 50(3):262-263. 1995

http://www.soil.ncsu.edu/lockers/Gruver_J/PDF%20files/Whitebread/whitebreadpg1.pdf

Stabilization of organic matter in temperate soils: mechanisms and their relevance under different soil conditions-a review. European Journal of Soil Science. 57:426-445. 2006. http://www.soil.ncsu.edu/lockers/Gruver_J/PDF%20files/Cstabilizationreview.pdf


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