Soil Resistance and Resilience to Compaction. EMAR.sssa

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Soil resistance and resilience to compaction.

EMAR.SSSA

DATASET SEPTEMBER 2015

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Per Schjnning

Aarhus University

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Soil resistance and resilience to

compaction as affected by theclay-organic carbon relation

ASA, CSSA, and SSSA International Annual MeetingsOct 16-19, 2011 San Antonio, TX

Emmanuel ArthurPer Moldrup

Per Schjnning

Lis W. de Jonge


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Introduction Anthropogenic stresses imposed on soils challenge their

ability to function

Soil stability is characterized by its resistance and

resilience to imposed stress

Compaction by agricultural machinery increases bulk

density and reduces pore functions

ASA, CSSA, and SSSA International Annual Meetings. Oct 16-19. San Antonio, TX 2


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Introduction Soils resistance and resilience to compaction is driven

by several factors (water content, texture, clay type, organic matteretc.)

Hypothesis

The main driver governing resilience in soils is the level

of clay saturation by organic carbon



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IntroductionObjective

Assess the role of clay saturation by organic carbon in

soil resilience to compaction using three functional

indicators



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Methodology Functional indicators:

Void ratio, e

Air permeability, ka

Air filled porosity,



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Clay (kg kg-1)

0.08 0.12 0.16 0.20 0.24

Organiccarbon(kgkg-1)

0.008

0.012

0.016

0.020

0.024MFC

MCC

CCC

Saturated

Unsaturated

Methodology Soils 3 sandy loams:

~17 % clayDifferent long term management

= different organic carbon contents:

MFC = Mixed forage cropping

MCC = Mixed cash cropping

CCC = Cereal cash cropping


10g clay 1g OC (Dexter et al., 2008)


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Methodology Compaction test

drained to-100 hPa

(Void ratio, e;

air permeability, kaAir filled porosity, )

Freeze-thaw

cycles [FT]-10C & -100 hPa

Compaction (200kPa)@2mm/min

7 days-100 hPa

ASA, CSSA, and SSSA International Annual Meetings. Oct 16-19. San Antonio, TX

Rebound

recovery [RR](ka, , e)

7

Resistance (RST)

ka, , e

Wet-dry

cycles [WD]

saturation & 40C

ka, , e

100 cm3


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Methodology Quantification of resistance and resilience

Compression index, Cc, from Gompertz model

= applied stress

e = void ratio

a, b, c = model parameters


10exp exp( (log ))e a c b m

exp(1)c

bC

c Low Cc= high resistance to compaction


10/18

Methodology Quantification of resistance and resilience

Compression index, Cc, from Gompertz model

Absolute values (e, ka, )

Indexed values:

Resistance [RST] = Original value Value after compaction

Original value

Resilience [PR] = Original value Recovery value

Original value


Range : 0 1

0 = maximum resistance/resilience

1 = no resistance/resilience


11/18

Results Functional indicators prior to compaction (-100hPa)


MFC MCC CCC

Air permeability, ka (m2) 35.7 12.84a 43.7 8.50a 115.7 12.91b

Air-filled porosity, (m3 m-3) 0.10 0.007a 0.16 0.015b 0.21 0.010c

Void ratio, e (m3 m-3) 0.89 0.03a 0.85 0.02a 0.85 0.04a


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Results Compaction resistance (Cc)


Initial void ratio, e0(m

3m

-3)

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2

Compression

Index,

Cc

0.00

0.03

0.06

0.09

0.12

0.15

0.18

0.21

MFC MCC CCC Regression

MFC MCC CCC

Initial void ratio, e0 0.89a 0.85a 0.85a

Compression index, Cc 0.08

a

0.12b

0.15c

Regression slope 0.21a 0.31b 0.31b

Higher clay saturation = higher

compression resistance

Increasing initial void ratio has relatively

less impact on Cc for MFC


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StageRST RR WD FT

R

STandPR(airpermea

bility)

0

10

20

30

40

ns

ns

a ab a

abb

MFC MCC CCC

StageRST RR WD FT

0.0

0.2

0.4

0.6

0.8

1.0

1.2

ns

a

a

b

a

ab

b

a

ab b

(B)(A)

Results Resistance (RST) and resilience (PR)

Air permeabilityAbsolute values Indexed values



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Stage

RST RR WD FT

RSTandPR(voidratio)

0.0

0.2

0.4

0.6

0.8

1.0 ns

aab

b

aab

b

aab

b

MFC MCC CCC

StageRST RR WD FT

0.00

0.03

0.06

0.09

0.12

0.15

a

b

b

a

b

c

a

b

c

a

ab

b

(B)(A)


Void ratioAbsolute values Indexed values



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Stage

RST RR WD FT

RSTandPR(air-filledpo

rosity)

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

aba

bns

a

bb

ns

MFC MCC CCC

Stage

RST RR WD FT

0.0

0.2

0.4

0.6

0.8

1.0

a

b

b ns

ab

ab

a

ab

b

(B)(A)


Air-filled porosityAbsolute values Indexed values



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Results Relation between resistance and resilience (void ratio)


Resistance Index

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18

ResilienceIndex

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

Rebound recoveryWet-dry resilience

Freeze-thaw resilience

Regression line


17/18

Conclusions For differently managed soils, the clay-organic carbon

relation governs structural stability Increased saturation of clay by organic matter:

increased compaction resistance using and e as indicators

reduced the effect of initial void ratio on compressionresistance

Increased soil resilience after natural recovery, wet-dry and

freeze-thaw cycles



18/18

Acknowledgements Project

Soil Infrastructure, Interfaces, and Translocation Processes in InnerSpace (Soil-it-is)

Funding

Danish Research Council for Technology and Production Sciences

STAiR


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Soil Resistance and Resilience to Compaction. EMAR.sssa