Effects of long term soil organic matter restitution mode on soil heterotrophic respiration and soil biological properties.

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Effects of long term

soil organic matter restitution mode

on soil heterotrophic respiration

and soil biological properties.

P. Buysse, M. Carnol, S. Malchair, C. Roisin, M. Aubinet

Unit of Biosystem Physics

Francqui Chair 2011,

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Introduction

• Soil Heterotrophic Respiration (

SHR

): positive

feedback to global change in the future?

• Agricultural soils = potentially important

sources of CO

₂

.

Importance of crop management (e.g. Organic

Matter Restitution Mode = «

OM-RM

»)

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Scientific questions

1. Does long term (> 50 years) application of

different OM-RM cause differences in

SHR

fluxes

?

2. Do different OM-RM imply different

responses of SHR to Temperature

and Soil

moisture content?

3. Is the experimental set-up suitable to answer

these questions?

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Experimental design

– Situated in Liroux, near Gembloux

– 6 different OM-RM (

RM1  RM6

)

– 6 plots (repetitions) in each treatment: 10 by 70 (or 60) m

– All plots ploughed over 0-25 cm depth

1 4 2 6 3 5 1 6 1 5 4 2 3 5 4 3 2 1 6 3 6 2 1 4 5 2 5 1 6 3 4 1 3 4 5 6 2 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 24 m 24 m 6 m 6 m 24 m 24 m 11 7 m 11 7 m 24 m 24 m 24 m 24 m 4.5 m 10 m 4.5 m 10.5 m 5 m Borne à 4 m de la clôture 5 m Borne 10.5 m T1 T2 T3 T4 T5 T6 = = = = = = Rien

Pailles + Lisier + CIPAN Pailles + Lisier + CIPAN Fumier

Rien

Pailles + CIPAN

N.B. : A partir de 2009, les feuilles de betteraves sont restituées dans tous les traitements

Pulvérisations (largeur 24 m)

Remarque : en betteraves, centrer semoir sur traces de pulvérisations

Allée enherbée Allée enherbée

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Manual SHR flux measurements

• Studied OM-RM (in 3 out of the 6 repetition plots):

– RM 1: Control (exportation of all residues) – RM 4: Manure

– RM 6: Restitution of residues

• Weeded areas

(3 m by 3 m):

4 measurement points

 12 points/treatment

Francqui Chair 2011, UCL, 12th May 2011 1 4 2 6 3 5 1 6 1 5 4 2 3 5 4 3 2 1 6 3 6 2 1 4 5 2 5 1 6 3 4 1 3 4 5 6 2 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 24 m 24 m 6 m 6 m 24 m 24 m 11 7 m 11 7 m 24 m 24 m 24 m 24 m 4.5 m 10 m 4.5 m 10.5 m 5 m Borne à 4 m de la clôture 5 m Borne 10.5 m T1 T2 T3 T4 T5 T6 = = = = = = Rien

Rien

Pailles + CIPAN

N.B. : A partir de 2009, les feuilles de betteraves sont restituées dans tous les traitements

Allée enherbée Allée enherbée PRAIRIE ZOOTECHNIE 1 4 2 6 3 5 1 6 1 5 4 2 3 5 4 3 2 1 6 3 6 2 1 4 5 2 5 1 6 3 4 1 3 4 5 6 2 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 24 m 24 m 6 m 6 m 24 m 24 m 11 7 m 11 7 m 24 m 24 m 24 m 24 m 4.5 m 10 m 4.5 m 10.5 m 5 m Borne à 4 m de la clôture 5 m Borne 10.5 m T1 T2 T3 T4 T5 T6 = = = = = = Rien

Rien

Pailles + CIPAN

N.B. : A partir de 2009, les feuilles de betteraves

sont restituées dans tous les traitements

Allée enherbée Allée enherbée

PRAIRIE ZOOTECHNIE

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Manual SHR flux measurements

– From 2 April to 30 July 2010 (14 measurement dates).

– Dynamic closed chamber system ([CO

₂

] vs Time).

– Measurements of Temperature and Soil moisture

content.

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Temporal evolutions of SHR fluxes and

Soil temperature

0

10

20

30

40

0.0

1.0

2.0

3.0

4.0 23/03

12/04

02/05

22/05

11/06

01/07

21/07

10/08

So

il

t

em

pera

tur

e [

°C]

So

il

r

espir

at

ion

flux

[µmo

l

CO

2.

m

-2

.s

-1

]

Date

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0.00

0.10

0.20

0.30

0.40

0.0

1.0

2.0

3.0

4.0 23/03

12/04

02/05

22/05

11/06

01/07

21/07

10/08

So

il

w

at

er

cont

ent

[%

V

ol.]

So

il

r

espir

at

ion

flux

[µmo

l

CO

2

.m

-2.

s

-1

]

Date

Control

Manure

Residues

SM

Temporal evolutions of SHR fluxes and

Soil moisture content

Francqui Chair 2011, UCL, 12th May 2011

IMPORTANT SPATIAL VARIABILITY

Normalization of the fluxes:

for each collar, division of the fluxes by the average over the season

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SHR fluxes vs Temperature

OM-RM R15 Q10 R²

1 0.8 1.31 0.32

2 0.63 1.46 0.15  R15 and Q10 factors: No significant difference_{between treatments (ANOVA, p > 0.05)}

0

0.5

1

1.5

2

2.5

5

10

15

20

25

30

35 A

ver

ag

e

-normaliz

ed

SHR flux

es

[-]

Temperature [°C]

Control Manure Residues

Q10 model - Control Q10 model - Manure Q10 model - Residues

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0

0.5

1

1.5

2

2.5

3

0.0

0.1

0.2

0.3

0.4

0.5 Normaliz

ed

SHR

flux

es

[-]

Soil moisture content [m³.m

-3

_]

Control Manure Residues

SHR fluxes vs Soil moisture content

- No clear direct relationship between SHR fluxes and SM content. - Very few points at high SM content.

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Increase of SHR fluxes after increase of SM

content between two measurement dates.

0

0.5

1

1.5

2

2.5

3 0.01 - 0.03

0.04 - 0.08

0.09 - 0.14

Ra

tio

of normal

iz

ed

flux

es

[-]

Class of Soil moisture content difference [m

3.

_m

-3

_]

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SHR fluxes Relative difference (%)

Control vs Manure 22.4 Control vs Residues 22.0 Residues vs Manure 19.6

Spatial variability issue

Francqui Chair 2011, UCL, 12th May 2011 14

SOC content Relative difference

Control vs Manure 25.6 Control vs Residues 15.8 Residues vs Manure 10

 Does spatial variability preclude the assessment of potential differences between treatments?

SHR Fluxes Relative uncertainty (%)

Control 17.3 Manure 14.1 Residues 13.6

Only differences between « Control » and « Manure » could potentially be assessed. The amount of measurement points should be min. 9, 24 and 45 to assess differences between Control/Manure, Control/Residues and Residues/Manure respectively.

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Main findings and discussion

• Question 1: SHR flux differences between the treatments?

No.

 Potential reasons:

- Problem of spatial variability

- Impact of drought  low fluxes  smaller differences

• Question 2: Different responses to T° and SM content?

 No.

 The study showed a strong SHR response to rewetting events.

 Birch effect? Solubilization of labile carbon?

• Question 3: Is the experimental set-up sufficient?

 Not totally. Because of the very important spatial variability more

measurement points would be necessary.

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Perspectives

• New flux measurement campaign in 2011

• Further investigation: « What are the effects

of long term application of different OM-RM

on

soil biological properties

(microbial

biomass, metabolic activity, qCO

₂

, labile

carbon)? »

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Types of OM-RM

Description of treatment

RM 1 Control (exportation of residues)

RM 2 Straw + liquid manure RM 3 Straw +liquid manure

RM 4 Exportation of residues + Manure

RM 5 Restitution of residues

RM 6 Restitution of residues

Today’s situation.

RM 2, 3 and 5 changed before and after 1998. RM 1, 4 and 6 were left unchanged since 1959.

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0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3 1955

1965

1975

1985

1995

2005

2015

So

il

ca

rbo

n

co

nt

ent

[

%

]

Year

Control

Manure

Restitution of residues

SOC temporal evolution

Mean differences of :

- 10 % between « Manure » and « Restitution of Residues » - 15.8 % between « Control » and « Restitution of residues » - 25.6 % between « Control » and « Manure »