Titel Federal Research Station Agroscope ART C- and

Titel Federal Research Station Agroscope ART C- and N-budgets of managed grassland Swiss Carbo. Europe/Nitro. Europe site C. Ammann, A. Neftel, C. Flechard, C. Spirig, J. Fuhrer Agroscope ART Research Station, Zürich, Switzerland Carbo. Europe-IP Meeting, Poznan, 2007

Site Fields Oensingen Field Site annual distribution of wind directions 0 N 200 150 local S N scale [m] 100 50 Hi Intensively managed grassland • mineral fertilizer and manure (ca. 200 kg/ha/y total N) • 4 -5 cuts per year y wa gh 0 -50 Extensively managed grassland • no fertilizer • 3 cuts per year -100 -150 -200 -300 Various crops (rotation) -250 -200 -150 -100 -50 local W E scale [m] 0 50 100 Eddy covariance systems

C-budget concept Components of the Grassland Carbon Budget (forage production, no grazing) CO 2 exchange (NEE) harvest manure DC/Dt carbon sequestration: DC/Dt = S(import/export processes) = NBP

C-comp_time Vegetation Development and Management Events

Carbon Budget for Intensive and Extensive Management (2002 -2005) CO 2 Manure DC/Dt C-budget result Harvest

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

N-Budget Oensingen Site: N-Budget Components Wet-only sampler Wet Depostion 15 N isotopic labelling on 6 subplots N-content in manure and synthetic fertilizer Gradient system (2 Ai. RRmonia units) N 2 – Fixation NH 3 – bidirectional exchange N content in harvest biomass 4 automated static chambers NO/NO 2 Exchange N 2 O – Emission and Uptake 3 dynamic chambers Run-off (dissolved NO 3 -) 2 suction cups N 2 – total Denitrification incubation with acetylene

Foto gradient Gradient system for NH 3 Dynamic chamber system for NO / NO 2 Static chamber system for N 2 O

Cumulative NH 3 Exchange (INT field)

N-budet result N-budet Annual N-Budget for Intensive and Extensive Management

. . . C-Budget. .

comp N-budget Comparison of N-Budget Estimates

comp N-budget Conclusions v A carbon sequestration is only observed for the fertilized grassland (high N input). v 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) v The carbon sequestration of the intensive field is partly (c. 20%) compensated by emission of N 2 O (due to fertiliser application)

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