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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

slide2

Global C cycle

Gt = 109 t = Pg = 1015 g

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

slide4

Relative contributions of major greenhouse gases:

H20 vapor - 36-70%

CO2 – 9-26%

CH4 – 4-9%

slide9

~ 1600 Gt globally

< 5 % of the mass of most soils

C

Mineral particles

slide10

SOM is a complex mixture

Living organisms

Biologically active SOM

Recent residues

Recalcitrant

SOM

Adapted from Magdoff and Weil (2003)

slide11

POM

IOM

DOM

ed

Are these materials components of humus ?

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

slide12

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
slide13

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

slide14

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)

slide15

Location within the soil matrix affects SOM dynamics

Free POM

Sensitivity to management

Intra-aggregate POM

Mineral associated OM

Adapted from Carter (2002)

slide16

SOM

pools

< 1 year

decades

What is the mean residence time of SOM ??

centuries

Janzen (2006)

slide17

Many studies have shown that physical fractions 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

slide18

Functional impact of SOM fractions

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

slide19

Humus adsorbs ions and molecules

Adapted from Brady and Weil (2002)

slide21

Humus increases plant available H20

Adapted from Brady and Weil (2002)

slide22

Aggregates form around particulate organic matter (POM)

Processes that disrupt aggregates accelerate loss of POM

slide24

SOM reduces bulk density

Magdoff and Weil (2004)

slide25

Do not till or traffic on wet soils !!!

Structural

damage

Soils with high C

are more resistant to

structural damage !

(Watts and Dexter, 1997)

slide27

The Soil Stomach

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

slide28

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

slide30

Blechh !!!

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)

slide33

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

Webb et al.(2003)

slide34

Microorganisms behave very

differently

in a petri dish

than they do in

soils

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

slide35

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

slide37

As a result,

most soil microorganisms are in a dormant state

For their prince charmings

to arrive !

waiting…

slide38

Roots

Rain

There are many types of prince charmings !

Tillage

Organic Amendments

slide39

Impact of earthworms on SOM dynamics

Ingested soil

Fresh casts

Aging casts

Soil profile

?

Assimilation Comminution

Nutrient release

Physical protection

(Lavelle and Spain, 2001)

slide40

The priming effect of plant roots

AggregateDisruption

Exposition of organic matter

GrowingRoot

Priming Effect

Exudation

Activation of microorganisms

(Lavelle and Spain, 2001)

slide41

Crop related changes in mineralizable N

No Till

Plow/Disk

Sorghum

Wheat

Soybean

Adapted from Magdoff and Weil (2004)

slide42

Climate affects SOM dynamics

Organic matter

accumulation

Brady and Weil (2002)

70 F

slide43

Landscape position affects SOM dynamics

Poorly drained

Interstream divide

Somewhat poorly drained

Moderately well drained

LANDSCAPE POSITIONS

Well drained

Poorly drained

Interfluve

Shoulder

Valley floor

SOIL DRAINAGE CLASSES

Backslope

slide46

How much

is enough ??

slide47

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

slide49

There are many ways to “measure” SOM

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)

slide50

Soil from a long term experiment in Beltsville, MD

20 yrs sod,

5 yrs CT

corn

25 yrs

CT corn

slide51

Relatively small differences in SOC

Large differences in soil function

After adding water

1.4 % C

140 bu/a

48 bu/a

1.0% C

slide52

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

slide54

NC STATE UNIVERSITY

DEPARTMENT of SOIL SCIENCE

Small increases in OM can improve macro-aggregation

Superior air/water relationships

Healthier root growth and function

(justification statement)

slide55

Crop residues

Cover Crops

Animal manure

Crop residues

20 years of similar tillage intensity

but contrasting levels of organic inputs

slide57

More OM is needed to stabilize fine textured soils

16 % clay

39 %

49%

39 %

49%

16 % clay

Adapted from Russell (1973)

slide58

Young particulate organic matter (POM) contributes to disease suppression

Disease Suppression

Damping off

Adapted from Stone et al. (2004)

slide59

Permanganate oxidizable C

a routine test for “active” soil C ??

slide61

Crop growth response to no-till planting with a rye 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

slide63

A systems approach

Well adapted crop

SOM

Nutrient

Management

Water

Management

Adapted from Bailey and Lazarovits (2003)

slide64

well mixed vs.

stratified

Conventional tillage

Conservation tillage

Adapted from House and Parmelee (1985)

slide67

Crop

residues

slide68

Multi-functional cover crops

Cover Crops

Cover crop

Adapted from Magdoff and Weil (2004)

slide71

Crop Rotation

High residue crops

Cover crops

Forages

slide73

Large scale composting

pH

Soluble salts

Herbicide residues

Trash

?

slide75

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)

slide76

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)

slide77

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

slide80

Carbon Trading

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

slide83

An excellent literature review

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

slide84

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