Tillage methods influence greenhouse gas emissions and soil C/N stock changes in winter oilseed rape cultivation

Transcription

1 Tillage methods influence greenhouse gas emissions and soil C/N stock changes in winter oilseed rape cultivation M. Andres 1, V. Huth 1 and J. Augustin 1 1 (ZALF), Institute for Landscape Biogeochemistry, Eberswalder Str. 84, DE Müncheberg Greenhouse Gas Emission from Oilseed rape Cropping and Mitigation Options Braunschweig Germany 4 th 5 th March 2015 The production of biofuels from rapeseed is suspected to enhance greenhouse gas emissions (climate impact) and losses from soil C and N stocks. The mitigation is hampered due to its dependency on numerous interacting factors: Site and climate variability Fertilizer type & amount Management factors e.g. tillage practice Contradictory information: Decreased and increased N 2 O emissions (e.g. Rochette 2008) Inconsistent information: Soil C increase in no-till systems (e.g. Paustian et al. 2000) 1

2 Find out if alternative tillage variants help to mitigate negative impact Field experiment in the North-eastern German Lowlands: Loamy sand (Haplic Luvisol) MAT 8.4 C and AP 486 mm Treatments, equally fertilized by 180 kg N ha -1 CAN: Conventional tillage (ploughing, control) No-till Mulch-till Jungkunst et al Black Box model: NEE N 2 O GPP R eco CH 4 Imput fertilizer-c Export harvest-c 2

3 Gas flux measurements: N 2 O/CH 4 Non-steady-state non-flow-through chamber measurements (Livingston and Hutchinson 1995) Enclosure time 1 h and 20 min. intervall sampling Flux calculation according to Pedersen et al Gap filling via linear interpolation N 2 O CH 4 Gas flux measurements: CO 2 Non-steady-state flow-through chamber measurements (Drösler 2005) Ecosystem respiration (Reco) measured by non-transparent chambers Net ecosystem exchange (NEE) measured by transparent chambers Gross primary production (GPP) determined by difference between NEE and Reco Flux and error calculation according to Hoffmann et al Gap filling by using temperature and radiation based models 3

4 Soil C budget approach: SC = C uptake + CH 4 -C + NEE - C fertilizer Climate balance (impact): CB = N 2 O-CO 2 eq + C-budget-CO 2 eq + CH 4 -CO 2 eq Preliminary results

5 N 2 O emissions treatment N 2 O in kg N ha -1 RD No-till 3.1 ± 0.2 RM Mulch-till 5.7 ± 1.8 RP conventional 2.9 ± /90 kg N ha -1 Harvest N 2 O emissions treatment N 2 O in kg N ha -1 RD No-till 4.4 ± 0.1 RM Mulch-till 5.2 ± 0.9 RP conventional 3.7 ± /90 kg N ha -1 Harvest 5

6 The intensity of N 2 O emissions seem to be stronger influenced by the soil tillage method than by climate variability. The intensity of CO 2 emissions seem to be stronger influenced by the climatic variability than by the soil tillage method. Mulch-till seem to be a good option for soil C stock gain, independently from interannual climate variability. Whereas the conventional tillage method lead to soil C stock losses. Mulch-till seem to be a good option for positive climate impact (cooling effect) but mitigation options in no-till system are considerably less. Whereas the conventional tillage method lead to negative effects. Open questions Long-term effect? Continue measurements. How does the crop type effects these budgets and balances? Detect potential mid-term crop effects. Is there accumulated carbon? Measure soil C within soil profile with a spatially high resolution. motivation methods results outlook 6

7 Thanks to you for listening! And many thanks for support to: Roland Fuß Mathias Hoffmann Judit Laufer Many other people for getting the measurements realized! Monique Andres 7