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This fact sheet takes a closer look at the multifaceted role of agriculture in climate change. Various scientific findings are presented that show the potential of organic farming to mitigate climate change.

Die Landwirtschaft spielt im Klimawandel eine bedeutende Rolle. Als Verursacherin von Klimagasen trägt sie einerseits zur globalen Erwärmung bei, verfügt aber andererseits auch über ein grosses Potenzial zur Minderung des Klimawandels. In diesem Faktenblatt wird die vielseitige Rolle der Landwirtschaft im Klimawandel näher beleuchtet. Dabei werden verschiedene wissenschaftliche Erkenntnisse dargestellt, die das Potenzial des Biolandbaus zur Minderung des Klimawandels zeigen.

L’agriculture joue un rôle important dans le changement climatique. D’une part, ses émissions de gaz à effet de serre contribuent au réchauffement mondial; d’autre part, elle dispose d’un fort potentiel d’atténuation du changement climatique. Cette fiche d’information met en exergue le rôle multifactoriel de l’agriculture dans le changement climatique et présente différentes connaissances scientifiques mettant en évidence le potentiel d’atténuation du changement climatique de l’agriculture biologique.

Under the United Nations Framework Convention on Climate Change (UNFCCC), industrialized countries and countries with economies in transition (so called Annex 1 countries) are encouraged to move towards more sophisticated approaches for national greenhouse gas reporting. To develop a model-based approach for estimating nitrous oxide (N2O) emissions from agricultural soils, model calibration is one of the first important steps. Extensive multisite field observations are necessary for this purpose, as agricultural management in Western Europe is complex (e.g., diverse crop rotations, different types of fertilizer and soil tillage). In the present study, we used ca. 24,000 daily N2O flux observations from six cropland sites, two in France and four in Switzerland, to conduct an automatic data-driven calibration of the biogeochemical model DayCent. This model is planned to be used for greenhouse gas reporting in the entire European Union as well as in Switzerland. After a site-specific calibration, a leave-one-out (LOO) cross-evaluation was conducted to assess the model’s ability to predict N2O emissions for sites it was not calibrated for. Mean observed N2O fluxes for 54 interactions of crop cycles, field studies and treatments were used to evaluate the model. The LOO cross-evaluation resulted in a R2 of 0.63 for the prediction of mean N2O fluxes per crop cycle, compared to an R2 of 0.51 obtained with default parameterization. Our results showed that the improvement in N2O predictions was associated with the adjustment of only seven parameters controlling the N cycle in soil (e.g., the maximum daily nitrification amount and the inflection point for the effect of water-filled pore space on denitrification) out of several hundred parameters. These parameters showed a wide range of values between sites, revealing an important challenge for calibration-based improvement of N2O simulations. Despite the remaining uncertainty, our model-based estimates of N2O emission per crop

La présente fiche d’information met en exergue le rôle multifactoriel de l’agriculture dans le changement climatique et présente différentes découvertes scientifiques mettant en évidence le potentiel d’atténuation du changement climatique de l’agriculture biologique.

Despite the increase in organic cropland, knowledge on the impact of organic farming on soil-derived nitrous oxide (N2O) and methane (CH4) emissions is rather limited. To improve the knowledge base, N2O and CH4 fluxes were investigated in a 571 day lasting cropping sequence in the “DOK” field trial. Two organic and two non-organic farming systems and an unfertilized control were chosen. For the whole monitoring, the two organic systems combined emitted 40% less N2O than the two non-organic ones cumulated on area-scale. Yield-scaled cumulated N2O emissions were nearly 10% lower for the organic systems combined, despite the yield gap of 27%. We found that besides N input, management induced soil quality properties drive differences in N2O emissions between farming systems as well. This supports the effort to invest in soil quality by ecological intensification not only to lower the environmental burden of agriculture but also to mitigate greenhouse gases

There is an urgent need to identify and evaluate management practices for their biophysical potential to maintain productivity under climate change while mitigating greenhouse gas (GHG) emissions from individual cropping systems under specific pedo-climatic conditions. Here, we examined, through DayCent modeling, the long-term impact of soil management practices and their interactions on soil GHG emissions and GHG intensity from Swiss cropping systems. Based on experimental data from four long-term experimental sites in Switzerland (Therwil, Frick, Changins, and Reckenholz), we robustly parameterized and evaluated the model for simulating crop productivity, soil C dynamics and soil N2O emissions across a range of management practices and pedo-climatic conditions. Net soil GHG emissions (NSGHGE) were derived from changes in soil C, N2O emissions and CH4 oxidation. Soils under conventional management acted as a net source of soil GHG emissions (1361–1792 kg CO2eq ha−1 yr−1) and NSGHGE were dominated by N2O (50–63%). Reduced tillage and no-tillage reduced long-term NSGHGE by up to 31 and 58%, respectively. Organic farming, represented by organic fertilization, reduced NSGHGE by up to 31% compared to systems based solely on mineral fertilization. Replacement of slurries with a composted FYM led to an additional reduction in NSGHGE by 46%, although our approach considered only soil GHG emissions and thus did not take into account GHG emissions from the composting process. Cover cropping did not significantly influence NSGHGE, however vetch tended to reduce NSGHGE (-19%). The highest mitigation potential was associated with organic farming plus reduced tillage management, it reduced long-term NSGHGE by up to 128%. Soil C sequestration accounted, on average, for 89% of GHG mitigation potentials, consequently N2O dominated NSGHGE across all treatments and sites (60 − 80%). This indicates that these mitigation potentials are time limited and reversible, if the management is

It is anticipated that organic farming systems provide benefits concerning soil conservation and climate protection. A literature search on measured soil-derived greenhouse gas (GHG) (nitrous oxide and methane) fluxes under organic and non-organic management from farming system comparisons was conducted and followed by a meta-analysis. Up to date only 19 studies based on field measurements could be retrieved. Based on 12 studies that cover annual measurements, it appeared with a high significance that area-scaled nitrous oxide emissions from organically managed soils are 492 ± 160 kg CO2 eq. ha− 1 a− 1 lower than from non-organically managed soils. For arable soils the difference amounts to 497 ± 162 kg CO2 eq. ha− 1 a− 1. However, yield-scaled nitrous oxide emissions are higher by 41 ± 34 kg CO2 eq. t− 1 DM under organic management (arable and use). To equalize this mean difference in yield-scaled nitrous oxide emissions between both farming systems, the yield gap has to be less than 17%. Emissions from conventionally managed soils seemed to be influenced mainly by total N inputs, whereas for organically managed soils other variables such as soil characteristics seemed to be more important. This can be explained by the higher bioavailability of the synthetic N fertilisers in non-organic farming systems while the necessary mineralisation of the N sources under organic management leads to lower and retarded availability. Furthermore, a higher methane uptake of 3.2 ± 2.5 kg CO2 eq. ha− 1 a− 1 for arable soils under organic management can be observed. Only one comparative study on rice paddies has been published up to date. All 19 retrieved studies were conducted in the Northern hemisphere under temperate climate. Further GHG flux measurements in farming system comparisons are required to confirm the results and close the existing knowledge gaps.

Farming practices are known to exert strong control over the soils’ function to act as sources or sinks for greenhouse gases (GHG). This paper deals with the outcome of a recent meta-analysis based on the evaluation of 19 published long-term farming system comparisons. It provides a comprehensive data base regarding GHG fluxes from soils under organic and non-organic management. There is scientific evidence for lower nitrous oxide emissions from organically managed soils when scaled to the area. However, further data from farming system comparisons are required, particularly from long-term GHG measurements covering several cropping seasons or ideally entire crop rotations. This enables closing knowledge gaps concerning N fluxes and pools under organic management as well as the formation of the new soil ecosystem (soil quality) equilibrium after implementing organic practices. Substantial reductions of nitrous oxide emissions as well as enhancement of methane uptake can be reached by consequent application of “good agricultural practice” and simple adoptions of soil management, forming together a balanced set of GHG mitigation mechanisms. In addition we provide first GHG flux data from the well-known DOK farming system trial in Therwil/CH and the role of microbial communities driving soil functioning.

Biologische Landwirtschaft fördert Bodenerhalt wie –Fruchtbarkeit und mindert bodenbürtige Treibhausgas- (THG)-Emissionen. Der globale Datensatz publizierter Messungen von THG-Flüssen, Lachgas (N2O) und Methan (CH4), in Böden unter biologischer (bio) und konventioneller Bewirtschaftung (kon) landwirtschaftlicher Systemvergleichen wurde mit Meta-Analyse und Meta-Regression untersucht. Ende 2012 waren 19 Studien, auf der nördlichen Hemisphäre in gemässigten Klimata realisiert, publiziert. 13 basieren auf Jahresmessungen. Daraus resultieren, mit generell p<0.001, für Acker- und Grasland zusammen 486±191 kg CO2-eq. (1.04±0.41 kg N2O-N) ha-1 a-1 niedrigere N2O Emissionen unter bio. Für Ackerland sind die N2O Emissionen unter bio 472±195 kg CO2-eq. ha-1 a-1 geringer, jedoch 52±32 kg CO2-eq. t-1 TS Ertrag höher. Eine 9% Ertragssteigerung gliche diesen Unterschied aus. In kon Böden werden die N2O Flüsse in signifikanter Weise durch die Menge des Stickstoff (N) Eintrags beeinflusst. Unter bio sind andere Parameter, wie Bodeneigenschaften, wichtiger. Die biologische Verfügbarkeit synthetischen N-Düngers der kon ist hoch. Die notwendige Mineralisierung der N-Quellen unter bio führt zu einer niedrigeren und verzögerten Verfügbarkeit. Die CH4 Senkleistung bio Ackerlands ist 3.1±3.3 kg CO2-eq. ha-1 a-1 (p=0.06) höher. Nassreisfelder, eine Studie, weisen unter bio reduzierte N2O Emissionen, aber 1097±242 kg CO2-eq. ha-1 a-1 höhere CH4 Emissionen auf. Weitere Messungen sind nötig, um vorliegende Resultate zu bestätigen, weitere pedo-klimatische Situationen und Wissenslücken abzudecken.

In their letter, Leifeld et al. (1) argue that our metaanalysis to identify differences in soil organic carbon (SOC) between organic (OF) and nonorganic farming [conventional farming (CF)] (2) selected CF systems that were nonrepresentative. This was not the case. We included data from all available pairwise field comparisons between OF and CF identified in the literature. The observed difference in external carbon (C) inputs between OF and CF did not result from a bias in the selection of studies/treatments but was attributable to the fact that the field comparisons we analyzed (2) were not from fertilization experiments but from pairwise farming system comparisons where the design and the underlying treatments reflected the current farming practices in the region in which the studies were conducted at the time the experiments were initiated.

Life expectancy tests performed on ceramic rings of compositions EC-55, EC-64, EC-65 and EC-69 have resulted in extensive data regarding the effects of impact shocks on the physical and electrical characteristics of the ceramic rings. The results have indicated that the dissipation and the mechanical Q of the ceramic were the parameters most affected by impact shocks. The dielectric constant was the only electrical characteristic that remained stable under impact shock. Ceramic rings of composition EC-65 were able to withstand higher and more impact shocks than rings of the other three compositions. The results on composition EC-69 indicated that this composition has the lowest mechanical strength with respect to impact shock. The results obtained from life expectancy tests performed on ceramic discs and rings were in agreement regarding the effects of impact shock on their electrical characteristics. The mechanical strength of the ceramic ring configuration was better than that of the ceramic disc configuration. This was true for all four ceramic compositions studied. (Author)