Theoretical and practical limitations of the acetylene inhibition technique to determine total denitrification losses
- 1Agroscope Reckenholz-Tänikon Research Station ART, Air Pollution/Climate, Reckenholzstrasse 191, 8046 Zürich, Switzerland
- 2Institute of Environmental Geosciences, University of Basel, Bernoullistrasse 30, 4056 Basel, Switzerland
- 3INRA, Agrocampus Ouest, UMR1069 SAS, Rennes, France
Abstract. The loss of N2 from intensively managed agro-ecosystems is an important part of the N budget. Flux monitoring of N2 emissions at the field scale, e.g., by eddy correlation or aerodynamic gradient method, is impossible due to the large atmospheric N2 background (78%). The acetylene (C2H2) inhibition technique (AIT) is a rather simple and frequently used, albeit imperfect, method to determine N2 losses from intact soil cores. In principle, AIT allows an estimation of total denitrification at high temporal resolution and on small spatial scales, with limited workload and costs involved. To investigate its potential and limitations, a laboratory system with two different detection systems (photoacoustic IR spectroscopy and gas chromatography) is presented, which allowed simultaneous measurements of up to 7 intact soil cores in air-tight glass tubes in a temperature controlled cabinet (adjusted to field conditions) with automated C2H2 injection. A survey of total denitrification losses (N2 + N2O) over 1.5 yr in soil cores from an intensively managed, cut grassland system in central Switzerland supports previous reports on severe limitations of the AIT, which precluded reliable estimates of total denitrification losses. Further, the unavoidable sampling and transfer of soil samples to the laboratory causes unpredictable deviations from the denitrification activity in the field.