Abstract. The loss of N 2 from intensively managed agroecosystems is an important part of the N budget. Flux monitoring of N 2 emissions at the field scale, e.g., by eddy correlation or aerodynamic gradient method, is impossible due to the large atmospheric N 2 background (78 %). The acetylene (C 2 H 2 ) inhibition technique (AIT) is a rather simple and frequently used, albeit imperfect, method to determine N 2 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 C 2 H 2 injection.A survey of total denitrification losses (N 2 + N 2 O) 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.

Abstract. Methane (CH 4 ) from ruminants contributes onethird of global agricultural greenhouse gas emissions. Eddy covariance (EC) technique has been extensively used at various flux sites to investigate carbon dioxide exchange of ecosystems. Since the development of fast CH 4 analyzers, the instrumentation at many flux sites has been amended for these gases. However, the application of EC over pastures is challenging due to the spatially and temporally uneven distribution of CH 4 point sources induced by the grazing animals. We applied EC measurements during one grazing season over a pasture with 20 dairy cows (mean milk yield: 22.7 kg d −1 ) managed in a rotational grazing system. Individual cow positions were recorded by GPS trackers to attribute fluxes to animal emissions using a footprint model. Methane fluxes with cows in the footprint were up to 2 orders of magnitude higher than ecosystem fluxes without cows. Mean cow emissions of 423 ± 24 g CH 4 head −1 d −1 (best estimate from this study) correspond well to animal respiration chamber measurements reported in the literature. However, a systematic effect of the distance between source and EC tower on cow emissions was found, which is attributed to the analytical footprint model used. We show that the EC method allows one to determine CH 4 emissions of cows on a pasture if the data evaluation is adjusted for this purpose and if some cow distribution information is available.

We compared (i) nitrous oxide (N 2 O) fluxes from a 9-month field experiment established on a temperate, newly sown, intensively managed meadow using automated chambers with fine time resolution, and (ii) fluxes measured at several occasions throughout the experiment under controlled laboratory conditions. Twenty tonnes dry matter ha −1 greenwaste biochar were added to three plots and compared with three control plots. Cumulated N 2 O field measurements revealed a reduction of 21.5% in the plots with biochar. The reductions for samples where the biochar was added at the beginning of the experiment in the field and samples which were collected each month and measured in the laboratory were in the same range (11.4-39.2%). Emission reductions from laboratory incubations when biochar was freshly mixed with soil in the laboratory were about twice as large (46.5-58.0%). Our results indicate provisionally that, at our site, biochar controls N 2 O emission through its capacity for reducing NO 3 − availability to denitrifiers, with the efficiency being related to the effectiveness of mixing of biochar in soil.

Abstract. Biochar, a carbon-rich, porous pyrolysis product of organic residues may positively affect plant yield and can, owing to its inherent stability, promote soil carbon sequestration when amended to agricultural soils. Another possible effect of biochar is the reduction in emissions of nitrous oxide (N 2 O). A number of laboratory incubations have shown significantly reduced N 2 O emissions from soil when mixed with biochar. Emission measurements under field conditions however are more scarce and show weaker or no reductions, or even increases in N 2 O emissions. One of the hypothesised mechanisms for reduced N 2 O emissions from soil is owing to the increase in soil pH following the application of alkaline biochar. To test the effect of biochar on N 2 O emissions in a temperate maize cropping system, we set up a field trial with a 20 t ha −1 biochar treatment, a limestone treatment adjusted to the same pH as the biochar treatment (pH 6.5), and a control treatment without any addition (pH 6.1). An automated static chamber system measured N 2 O emissions for each replicate plot (n = 3) every 3.6 h over the course of 8 months. The field was conventionally fertilised at a rate of 160 kg N ha −1 in three applications of 40, 80 and 40 kg N ha −1 as ammonium nitrate. Cumulative N 2 O emissions were 52 % smaller in the biochar compared to the control treatment. However, the effect of the treatments overall was not statistically significant (p = 0.27) because of the large variability in the data set. Limed soils emitted similar mean cumulative amounts of N 2 O as the control. There is no evidence that reduced N 2 O emissions with biochar relative to the control is solely caused by a higher soil pH.

Biochar application to agricultural soils has a significant potential to influence soil resource availability and thus crop performance. A factorial experiment investigating effects of different biochar application rates combined with nitrogen fertilizer was conducted in field conditions on a Haplic Luvisol. The aim of this study was to evaluate the effects of biochar and biochar combined with fertilization on soil organic matter and soil structure parameters. The treatments comprised combinations of biochar application of 0, 10 and 20 t ha

The benefits of biochar application are well described in tropical soils, however there is a dearth of information on its effects in agricultural temperate soils. An interesting and little explored interaction may occur in an intensive agriculture setting; biochar addition may modify the effect of commonplace N-fertilization. We conducted a field experiment to study the effects of biochar application at the rate of 0, 10 and 20 t ha

Abstract. Carbon (C) sequestration in the soil is considered as a potential important mechanism to mitigate greenhouse gas (GHG) emissions of the agricultural sector. It can be quantified by the net ecosystem carbon budget (NECB) describing the change of soil C as the sum of all relevant import and export fluxes. NECB was investigated here in detail for an intensively grazed dairy pasture in Switzerland. Two budget approaches with different system boundaries were applied: NECB tot for system boundaries including the grazing cows and NECB past for system boundaries excluding the cows. CO 2 and CH 4 exchange induced by soil/vegetation processes as well as direct emissions by the animals were derived from eddy covariance measurements. Other C fluxes were either measured (milk yield, concentrate feeding) or derived based on animal performance data (intake, excreta). For the investigated year, both approaches resulted in a small near-neutral C budget: NECB tot −27 ± 62 and NECB past 23 ± 76 g C m −2 yr −1 . The considerable uncertainties, depending on the approach, were mainly due to errors in the CO 2 exchange or in the animal-related fluxes. The comparison of the NECB results with the annual exchange of other GHG revealed CH 4 emissions from the cows to be the major contributor in terms of CO 2 equivalents, but with much lower uncertainty compared to NECB. Although only 1 year of data limit the representativeness of the carbon budget results, they demonstrate the important contribution of the non-CO 2 fluxes depending on the chosen system boundaries and the effect of their propagated uncertainty in an exemplary way. The simultaneous application and comparison of both NECB approaches provides a useful consistency check for the carbon budget determination and can help to identify and eliminate systematic errors.

Climate change can alter the habitat suitability of invasive species and promote their establishment. The highly polyphagous brown marmorated stinkbug, Halyomorpha halys Stål (Hemiptera: Pentatomidae), is native to East Asia and invasive in Europe and North America, damaging a wide variety of fruit and vegetable crops. In Switzerland, crop damage and increasing populations have been observed since 2017 and related to increasing temperatures. We studied the climatic suitability, population growth, and the number of generations under present and future climate conditions for H. halys in Switzerland, using a modified version of the bioclimatic model package CLIMEX. To address the high topographic variability in Switzerland, model simulations were based on climate data of high spatial resolution (approx. 2 km), which significantly increased their explanatory power, and identified many more climatically suitable areas in comparison to previous models. The validation of the CLIMEX model using observational records collected in a citizen science initiative between 2004 and 2019 revealed that more than 15 years after its accidental introduction, H. halys has colonised nearly all bioclimatic suitable areas in Switzerland and there is limited potential for range expansion into new areas under present climate conditions. Simulations with climate change scenarios suggest an extensive range expansion into higher altitudes, an increase in generations per year, an earlier start of H. halys activity in spring and a prolonged period for nymphs to complete development in autumn. A permanent shift from one to two generations per year and the associated population growth of H. halys may result in increasing crop damages in Switzerland. These results highlight the need for monitoring the spread and population development in the northwestern part of Switzerland and higher altitudes of the valleys of the south.