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Influence of soil tillage system on CO2, N2O and CH4 exchange, climate impact, and C/N budgets of winter oilseed rape in NE Germany

Monique Andres1, Vytas Huth1, Jürgen Augustin1
1 Institute of Landscape Biogeochemistry, Leibniz Centre for Agricultural Landscape Research (ZALF)

P 3.1 in Fluxes between the atmosphere and ecosystems

Poster Session 2 on Tuesday, 16:30-18:00

Despite increasing production of biofuels from rapeseed in Germany, there is an intensive discussion about the ecological impact of this cropping system. Since little is known about greenhouse gas emissions of N2O, CO2 and CH4 as well as climate balances of rapeseed cultivation systems for biofuel production, there is an urgent need to address these knowledge deficits. Therefore, we conducted field trials in 2012 to quantify direct GHG emissions located at the Great Plain Region of NE Germany. We present all-year measured and modeled CO2, CH4 and N2O fluxes of winter oilseed rape for i) no-till ii) mulch-till and iii) conventional tillage (ploughing, control). All three treatments were equally fertilized by 180 kg N as calcium ammonium nitrate.

CO2 flux measurements of ecosystem respiration (Reco), net ecosystem exchange (NEE) and gross primary production (GPP; calculated as difference between NEE and Reco) were conducted throughout the year every four weeks using a flow-through non-steady-state closed chamber system (Drösler 2005). Measurement gaps of Reco and NEE were filled by using temperature or radiation-based models, respectively. N2O and CH4 fluxes were measured bi-weekly using a non-flow-through non-steady-state closed chamber system (Livingston und Hutchinson 1995) with 20 minutes interval sampling and gap filling via linear interpolation. Based on the measured gas exchange (cumulated fluxes of CO2-C (Reco, GPP, NEE), N2O-CO2,eq and CH4-CO2,eq) climate balances can be calculated. In case of C/N budgets C and N output values (gas losses, yield) are subtracted from C and N input values (fertilization). All presented results refer to the first cropping season 2012–2013.

The CH4 emissions have played a rather negligible role. Furthermore, the annual direct N2O emissions also were at a low level, perhaps because of the weather conditions as 2013 were characterized by a cold and long winter with snow until mid-spring. There were no significant differences between the treatments. Since just minor N2O and CH4 fluxes occurred, the climate balances were predominately determined by CO2 emissions. The results varied widely between treatments from -498 g CO2-Ceq m-2 a-1 to +1340 g CO2-Ceq m-2 a-1 at the mulch-till system and the no-till system, respectively. The obtained results at the conventional tillage treatment were at a comparable level to the no-till treatment in terms of both N2O emissions and the CO2 emissions. Consequently, this results a climate balance of +1220 g CO2-Ceq m-2 a-1.

The intensity of gaseous C and N fluxes seems to be strongly influenced by interactions between soil C and N stocks and inter-annual climatic variability.

Letzte Änderung 04.04.2014