TitelTitel

C- and N-budgets C- and N-budgets of managed grasslandof managed grassland

Swiss CarboEurope/NitroEurope siteSwiss CarboEurope/NitroEurope site

C. Ammann, A. Neftel, C. Flechard, C. Spirig, J. Fuhrer

Agroscope ART Research Station, Zürich, Switzerland

CarboEurope-IP Meeting, Poznan, 2007

Federal Research Station Agroscope ART

Site FieldsSite Fields

Oensingen Field SiteOensingen Field Site

Intensively managed grassland• mineral fertilizer and manure

(ca. 200 kg/ha/y total N) • 4-5 cuts per year

Extensively managed grassland• no fertilizer • 3 cuts per year

Various crops (rotation)

Eddy covariance systems

-200

-150

-100

-50

0

50

100

150

200

-300 -250 -200 -150 -100 -50 0 50 100

local WE scale [m]

loca

l S

N s

cale

[m

]

Highway

0

N

annual distribution of wind directions

C-budget conceptC-budget concept

Components of the Grassland Carbon BudgetComponents of the Grassland Carbon Budget(forage production, no grazing)(forage production, no grazing)

C/C/tt

carbon sequestration: C/t

CO2 exchange (NEE) harvest

manure

= (import/export processes) = NBP

C-comp_timeC-comp_time

Vegetation Development and Management EventsVegetation Development and Management Events

-1

-0.5

0

0.5

1

1.5

2

2.5

Jan 2002 Jan 2003 Jan 2004

harvest export EXT [tC/ha]

harvest export INT [tC/ha]

manure import INT [tC/ha]

-7

-6

-5

-4

-3

-2

-1

0

1

Jan 2002 Jan 2003 Jan 2004 Jan 2005

cum

ulat

ive

NE

E [

tC h

a-1

]

NEE (INT)

NEE (EXT)

C-budget resultC-budget result

Carbon BudgetCarbon Budgetfor Intensive and Extensive for Intensive and Extensive Management (2002-2005)Management (2002-2005)

C/t

CO2

HarvestManure

-6

-4

-2

0

2

4

6

carb

on e

xchange [tC

ha-1

y-1

]

intensive field

extensive field

NEE (CO2) + Hexport - Mimport = C-budget

-5

-4

-3

-2

-1

0

1

2

3

2002 2003 2004 2005

diff

eren

ce in

net

ca

rbo

n ex

chan

ge [t

C h

a-1 y

-1]

R_hetero (lab)R_hetero (lab)

0

500

1000

1500

0-5 cm 5-10 cm 25-30 cm 0-5 cm 5-10 cm 25-30 cm 0-5 cm 5-10 cm 25-30 cm

soil layer

hete

rotr

oph

ic C

O2

prod

uctio

n [m

g-C

g-S

OC

-1 d

-1]

int

ext

2002 2003 2004

N.A. N.A.

Heterotrophic Soil RespirationHeterotrophic Soil Respiration(incubated soil cores at 25°C)(incubated soil cores at 25°C)

N-BudgetN-Budget

NO/NO2-Exchange N2O – Emission

and Uptake

NH3 – bidirectional exchange

Run-off (dissolved NO3-)

N2 – Fixation

Bo

Ammonium (NH4+)

Nitrifikation Denitrifikation

NO N2O N2ONO

Nitrat (NO3-)

MolekularerStickstoff (N2)

Sauerstoff Wasser

DiffusiverTransport zurBodenoberfläche

Bodenoberfläche

N-content in manure and synthetic fertilizer

3 dynamic chambers

4 automated static chambers

15N isotopic labelling on6 subplots

Gradient system (2 AiRRmonia units)

N content in harvest biomass

2 suction cups

Oensingen Site: N-Budget ComponentsOensingen Site: N-Budget Components

Wet Depostion

Wet-only sampler

N2 – total Denitrification

incubation with acetylene

Foto gradientFoto gradient

Gradient system for NH3

Static chamber system for N2O

Dynamic chamber system for NO / NO2

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

25.Jun

.06

15.Jul.06

04.Aug

.06

24.Aug

.06

13.Sep.06

03.Okt.06C

um

ula

tive

NH

3 fl

ux

(kg

NH

3-N

ha-1

)

DB1

DB2

Cumulative NHCumulative NH33 Exchange (INT field) Exchange (INT field)

N-budet resultN-budet result

Annual N-Budget for Intensive and Extensive ManagementAnnual N-Budget for Intensive and Extensive Management

-250 -200 -150 -100 -50 0 50 100 150

N-harvest

N-fertilizer

Wet deposition

NO

NO2

Runoff

N2O

NH3

N2 fixation

tot. Denit

Budget

N exchange [kgN ha-1 yr-1]

Intensive

Extensive

..........

C-Budget ....C-Budget ....

-6

-4

-2

0

2

4

6

carb

on e

xchange [tC

ha-1

y-1

]

intensive field

extensive field

NEE (CO2) + Hexport - Mimport = C-budget

comp N-budgetcomp N-budget

Comparison of N-Budget EstimatesComparison of N-Budget Estimates

-250 -200 -150 -100 -50 0 50 100 150

from N-fluxes

C-Budget + C/N ratio

N exchange [kgN ha-1 yr-1]

Intensive

Extensive

comp N-budgetcomp N-budget

ConclusionsConclusions

A carbon sequestration is only observed for the fertilized grassland (high N input).

The net carbon loss of the extensive field is probably due to an enhanced decomposition of soil organic matter ( N mobilisation due to lack of fertilisation)

The carbon sequestration of the intensive field is partly (c. 20%)

compensated by emission of N2O (due to fertiliser application)

EndEnd

Thank You