How defoliation frequency acts on N2O emission in grasslands?

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HAL Id: hal-02811419

https://hal.inrae.fr/hal-02811419

Submitted on 6 Jun 2020

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How defoliation frequency acts on N2O emission in grasslands?

Katja Klumpp, Tiphaine Tallec, Franck Poly, Olivier Darsonville

To cite this version:

Katja Klumpp, Tiphaine Tallec, Franck Poly, Olivier Darsonville. How defoliation frequency acts on N2O emission in grasslands?. EmiLi 2012 International Symposium on Emissions of Gas and Dust from Livestock, Jun 2012, Saint-Malo, France. pp.17. �hal-02811419�

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Evaluation de l’UREP 7 Avril 2008

A L I M E N T A T I O N

A G R I C U L T U R E

E N V I R O N N E M E N T

How defoliation frequency acts on N

₂

O emission in

grasslands?

Klumpp, Katja, Tallec, Tiphaine Poly, Franck

Darsonville Olivier

INRA, Grassland Ecosystem Research, Clermont Ferrand

(3)

• In agricultural sector, 46% of N

₂

O is emitted by soil through microbial activity: denitrification and nitrification

(IPCC 2007).

• Global N

₂

O emissions are estimated to increase at a rate of 0.25% per year

(IPCC, 2001)

• Soil management strategies may reduce emissions by 10 to 30%.

Context

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3

Grassland : at local scale N

₂

O emissions depend on

Velthof et al. 1996

Soil texture and management

Flechard et al. 2007 AGEE

% WFPS

Soil temperature (°C) Emission

Factor (%)

N supply, water filled pore space and soil

temperature

Environmental parameters and management

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(Klumpp & Bloor et al. 2010)

*

low clover density (15%) high clover density (35%)

DOY

Precipitation events

•Clover density and defoliation

• N2O emissions  with low clover content

• competition plant/microbs for N depending on clover density

• N2O emissions peak at after cuts

Grassland : N

₂

O emissions depend on

Management and community structure

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Rafique et al. (2012)

•Grazing and mowing events and N supply

grazing mowing grazing mowing

Nfert Nfert Nfert

Urea

Grassland : N

₂

O emissions depend on

However, N₂O emissions are difficult to ascribe to defolation events as other variables favouring emissions coincident

(e.g. Tsoil, WFPS, Nfert).

Management and N supply

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Grassland : N

₂

O emissions depend on

•C supply/availability

Denitrification-derived N₂O is triggered by organic matter with high labile C content (Senbayram et al. 2012)

Cutting-induced flushes in plant rhizodeposition and soil C availability may modify microbial activity (Ostle et al. 2007).

Management and nutrient availability

In a field experiment we tested following hypothesis

(i) High defoliation frequency will increase N₂O emissions (ext vs int) and

(ii) High defoliation enhances denitrifier activity by an potential increase in labile C (i.e. rhizodeposition (exudation, roots death) for microbes.

OBJECTIVES

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8 automated chambers +IRGA to measure

continuously (6times d^-1) N₂O, Hsoil and Tsoil

Permanent upland g ra ssland site F-Laqueuille

Alt. 1050m, mean T 8°C, 1000mm

Management 1.2 LSU ha.yr1

210 g N ha.yr1 (3 splits)

13.7 % clover

7 dominante species (36)

Prod: 7.1t DM green.ha.yr1 Standing: 2.6t DM.ha.yr1

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Experimental Setup

C + C -

• Cutting frequence ( 4 chambre)

C1 C2

25/05/10 Date

Fert NPK

70kg/ha C3 C4 C5

08/06/10

22/06/10

06/07/10

20/07/10 11/05/10

At cutting dates :

- aboveground biomass, litter and stubble mass - % clover

- Potential nitrification and denitrification activity (after 3 days) - pH, NH₄andNO₃ contents

DOY

0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320

cut

PreP 1 2 3 4 5 PostP

Nfert->

0

1 2 3 4 5 end start

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0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 N 2O (mg m-2 d-1 )

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

WFPS (mm)

-5 0 4050 6070 8090 100

C- C+

WFPS C- WFPS C+

Results: daily N

₂

O

Snow melting

Fertilisation effect

heavy rain event

C-<WFPS <C+

C+<WFPS <C- N?

Nfert->

Cut->

C + C -

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DOY

0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 N 2O (mg m-2 d-1 )

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

cut C- C+

PreP 1 2 3 4 PostP

P<0.1

P** P* P***

5

ns P*

Nfert->

ns

0

Period C+/C- Period C+

Results: daily N

₂

O

P**

C- C+ C+ C-

Fertilisation effect

heavy rain event

C-<WFPS <C+

C+<WFPS<C- N?

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DOY

100 150 200 250 300

cumulated N 2O (mg N 2O m-2 period -1 )

0 20 40 60 80 100

C-C+

cut

PreP 0 1 2 3 4 5 PostP

Cumulated C- = 107±11mg N₂O m^-2(EF 0.015) Cumulated C+ = 130±10mg N₂O m^-2(EF 0.018)

Results: cumulated N

₂

O over the cutting period

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pot. Denitrifaction (µg N-N2O/g/h) 0 1 2 3 4 5 6

DOY

100 150 200 250 300

NO 3(mg kg-1 )

0 10 20 30 40 50 cumulated N2O (mg N 2O m-2 period-1 )

0 20 40 60 80 100

C- C+

cut

PreP 0 1 2 3 4 5 Post P

Results: cumulated N

₂

O flux and microbial activities

* * * ns ns Cumulated N₂O

potential N₂O emission by denitrifying activity

 C- due to better NO₃ availability

Mineral soil NO₃ Denitrifying

activity

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pot. Nitrifaction (µg N-N2O/g/h) 0 1 2 3 4 5 6

DOY

100 150 200 250 300

NH4(mg kg-1 ) 0 2 4 6 8 10 cumulated N2O (mg N2O m-2 period-1 )

0 20 40 60 80 100

C- C+

cut

PreP 0 1 2 3 4 5 Post P

Cumulated N₂O

Mineral soil NH₄ Nitrifying

activity

Results: cumulated N

₂

O flux and microbial activities

potential N₂O emission by Nitrifying activity showed no effect

NH₄

availability in C-

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•Potential denitrifying activity increased with litter and green stubble mass and NO₃(p<0.05, R2=0.80)

•C+ Denitrifier activity was negatively related to mean N₂O emissions over the periode

(p<0.05, R2=-0.68)

C+ Denitrifier activity was positively related to %clover

(p<0.05, R2=0.58) DOY

120 140 160 180 200 220 0

1 2 3

DOY

120 140 160 180 200 220 0

1 2 3 4 5 6

C- C+

DOY

120 140 160 180 200 220 0

1 2

DOY

120 140 160 180 200 220 0

20 40 60 80

%clover Stubble (g) Litter (g) 100 Dry Mass (g)

Except for %clover in period 2,3 and 4 C+ < C-

Results: Microbial activity and other data

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Results: N

₂

O emissions and other data

Forward stepwise multiple regression analyses

Lg N₂O= -0.34 DMass – 1.8 NH₄– 1.1 stubble + 0.8 NO₃– 0.94 Denit – 0.45 pH

(p-model< 0.001, R2=0.62)

•C+ Lg N₂O= -1.2 Litter – 0.8 %clover -0.9 NH₄

(p-model< 0.01, R2=0.72)

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• C+ tended to have higher N₂O emissions probably due to higher clover fraction (i.e. N rich substrate) and labil C through cuts (3 out of 5 cut events).

• However, on annual basis this was out leveled due to other flux favouring variables (i.e. WFPS).

(C- 107±11; C+ 130±10 mg N₂O m^-2 )

• Our results indicate that not only amount and timing of N supply plays a role but also timing and frequence of

defoliation.

Conclusions

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How defoliation frequency acts on N2O emission in grasslands?

How defoliation frequency acts on N

O emission in

grasslands?

• In agricultural sector, 46% of N

O is emitted by soil through microbial activity: denitrification and nitrification

• Global N

O emissions are estimated to increase at a rate of 0.25% per year

• Soil management strategies may reduce emissions by 10 to 30%.

Context

Grassland : at local scale N

O emissions depend on

Grassland : N

O emissions depend on

Management and community structure

Grassland : N

O emissions depend on

Management and N supply

Grassland : N

O emissions depend on

Management and nutrient availability

Permanent upland g ra ssland site F-Laqueuille

C + C -

Results: daily N

O

Results: daily N

O

Results: cumulated N

O over the cutting period

Results: cumulated N

O flux and microbial activities

Results: cumulated N

O flux and microbial activities

Results: Microbial activity and other data

Results: N

O emissions and other data

Conclusions

Thank you