Olivier Heller

Soil functions such as water regulation, resistance to degradation (i.e., erosion) and habitat provision for soil biota are essential for climate‐resilient cropping systems. While soil functions are largely governed by pedo‐climatic conditions, the relative importance of agricultural management remains unclear. Because these functions are governed by soil physical properties, we quantified the relative influence of pedo‐climatic conditions and soil management on key soil physical properties across ten long‐term field experiments in Europe. The sites spanned a 2500 km climatic gradient from Spain to Sweden and included contrasting tillage or organic matter management practices. Measurements included bulk density (BD), water storage, aeration, hydraulic conductivity, soil organic carbon (SOC), aggregate stability, and earthworm abundance in topsoil (~10 cm) and subsoil (~30 cm) across 92 plots and 23 management treatments. Management intensities (carbon inputs, tillage, mineral nitrogen fertilisation) were quantified over the preceding decade. We applied mixed‐effects models, variance partitioning and structural equation modelling to identify direct and indirect effects. Pedo‐climatic conditions explained more variability in soil physical properties than management (threefold in the topsoil and eightfold in the subsoil). Mean annual temperature and clay content controlled topsoil SOC content, which in turn mediated most soil physical properties. Management effects, although smaller, significantly influenced topsoil properties. Higher C inputs increased SOC, aggregate stability and earthworm abundance. These effects indirectly reduced BD and penetration resistance while increasing water storage, air capacity and hydraulic conductivity. Higher tillage intensity reduced BD directly but was also associated with lower aggregate stability and reduced saturated hydraulic conductivity in the topsoil. Overall, pedo‐climatic conditions dominated soil physical properties, particularly in the subsoil, whereas management mainly affected topsoil properties relevant for climate resilience, highlighting limited subsoil responsiveness and the need for management strategies targeting subsoils.

Recent meta-analyses suggest risks of increased nitrate (NO3-) leaching with the implementation of reduced tillage practices. This study aimed to quantify effects of a subsidized and commonly implemented form of non-inversion tillage in Switzerland (NIT, i.e. chisel ploughing) in comparison to conventional tillage (CT, i.e. mouldboard ploughing) on NO3- leaching and its driving processes (i.e. water fluxes, soil temperature, plant uptake). A lysimeter experiment was conducted at the lysimeter facility Reckenholz/Zurich in Switzerland, mimicking tillage differences. Results after three years of treatment implementation show that during the following three years, tillage treatment had a significant effect on NO3- leaching in one of three seepage periods for two of three soil types considered. NIT reduced NO3- leaching in the seepage period 2014/2015 by 42 % on a Cambisol from Reckenholz and 32 % on a Luvisol from Schafisheim, respectively. The observed effect was driven by differences in NO3- concentrations in seepage water rather than seepage water amounts. Differences in NO3- concentrations could be attributable to structural differences in the topsoil, leaving larger amounts of soil N exposed to matrix water flow in the disturbed topsoil under CT than in the largely undisturbed topsoil under NIT. Also, differences in crop residue amount between treatments could have contributed to NO3- concentration differences. The treatment impact on NO3- leaching was most pronounced during and shortly after a bare soil period following sugar beet cultivation, which coincided with above-average spring precipitation. Considering that winter and spring precipitation is expected to increase with progressing climate change in Switzerland, reduced soil management may hold potentials to mitigate NO3- leaching in the face of progressing climate change. However, more research is needed to prove the relevance of this mechanism and its sensitivity to soil, climate and management drivers.

Soil compaction has negative impacts on soil ecosystem services, such as food production, groundwater recharge and climate regulation. The extent, magnitude, and spatio-temporal variability of the environmental and economic impacts of compaction remain unknown. In this study, we develop a novel framework that couples a soil-compaction-agroecosystem model with climate projections from the Coupled Model Intercomparison Project (CMIP6) to systematically predict changes in crop yield, nitrogen losses, soil carbon stocks and surface water runoff from compacted arable land across Europe. Simulations were conducted at 0.11’ spatial resolution under the high emissions Shared Socioeconomic Pathway (SSP585) scenario. This was done for winter wheat, the most widespread crop in Europe, by considering an ensemble of three compaction levels (representing wheel loads of 4, 6 and 8 Mg) and projections from five climate models. The simulation outcomes were used to estimate the economic costs of compaction. We compared compaction induced changes in variables related to soil ecosystem services for the Near Future (NF, centred about year 2030), Mid-term (MT, 2050) and End of Century time horizons (EOC, 2090). We estimated annual compaction induced economic cost due to losses of crop yield, carbon and nitrogen for Europe to be approximately 7 ± 0.3, 5 ± 0.5 and 2.7 ± 0.3 billion € per year for the NF, MT, and EOC, respectively, with the decreasing trend attributed to overall decreasing yields due to climate change. In addition, the continental economic cost of flooding by soil compaction induced increase in runoff were estimated as 3 ± 0.7, 3.1 ± 0.6 and 3.2 ± 0.5 billion € for the NF, MT and EOC, respectively. Our simulations indicate the negative impact of soil compaction on soil services under future climate scenarios, adding additional challenges for sustainable future agroecosystems. This further highlights the need to develop policies that protect soil by mitigating soil compaction through improved traffic management practices, soil recovery measures, and the development of new agricultural machinery.

Switzerland has a wide diversity of soil types that are subject to pressures of varying intensity and scale. Localised pressures such as compaction, sealing or heavy metal accumulation threaten both short‐ and long‐term soil fertility and food production. Large‐scale trends such as the intensive use of fertilisers or continued cultivation of organic soils can have effects on the ecosystem functioning of an entire region. Many of these pressures are concentrated on the Swiss plateau, which covers only about one third of the country and contains both the densest population and the most productive soils. We here review the main soil challenges of Switzerland and examine to which extent these challenges are addressed by different legal frameworks. Soil erosion, contamination as well as nutrient availability and use efficiency are all best described in the scientific literature and regulated by policies. In contrast, for several pressing soil challenges such as soil organic carbon loss, biodiversity loss or soil compaction only limited policy instruments are in place. We also report on the key findings of the 5‐year EJP SOIL project that aimed to address several of these soil challenges in research projects of different scale. We discuss the key findings relevant for Switzerland, and outline their implications for various stakeholder groups, including researchers, policy makers, farmers, land managers and advisors. This not only enhances the value of the research outputs for stakeholders but also demonstrates how a research programme of this scale can directly benefit different national stakeholder groups.

Recent meta-analyses suggest risks of increased nitrate leaching with the implementation of reduced tillage practices. This study aimed to quantify effects of a subsidized and commonly implemented form of non-inversion tillage in Switzerland (NIT, i.e. chisel ploughing) in comparison to conventional tillage (CT, i.e. mouldboard ploughing) on nitrate leaching and its driving processes (i.e. water fluxes, soil temperature, plant uptake). A lysimeter experiment was conducted at the lysimeter facility Reckenholz/Zurich in Switzerland, mimicking tillage differences. Results after three years of treatment implementation show that during the following three years, cumulative nitrate leaching was 26 % higher under CT than under NIT (i.e. 63 ± 10 kg/ha N with CT vs. 46 ± 9 kg/ha N with NIT). The observed effect was driven by differences in nitrate concentrations in seepage water rather than seepage water amounts. The beneficial effect of NIT on nitrate leaching was most pronounced during and shortly after a bare soil period following sugar beet cultivation, which coincided with above-average spring precipitation. These findings suggest that reduced soil management may hold the potential to reduce nitrate leaching during winter and spring wet spells with poor plant cover, which are expected to become more frequent with progressing climate change.

Recent meta-analyses suggest risks of increased nitrate leaching with the implementation of reduced tillage practices. This study aimed to quantify effects of a subsidized and commonly implemented form of non-inversion tillage in Switzerland (NIT, i.e. chisel ploughing) in comparison to conventional tillage (CT, i.e. mouldboard ploughing) on nitrate leaching and its driving processes (i.e. water fluxes, soil temperature, plant uptake). A lysimeter experiment was conducted at the lysimeter facility Reckenholz/Zurich in Switzerland, mimicking tillage differences. Results after three years of treatment implementation show that during the following three years, cumulative nitrate leaching was 26 % higher under CT than under NIT (i.e. 63 ± 10 kg/ha N with CT vs. 46 ± 9 kg/ha N with NIT). The observed effect was driven by differences in nitrate concentrations in seepage water rather than seepage water amounts. The beneficial effect of NIT on nitrate leaching was most pronounced during and shortly after a bare soil period following sugar beet cultivation, which coincided with above-average spring precipitation. These findings suggest that reduced soil management may hold the potential to reduce nitrate leaching during winter and spring wet spells with poor plant cover, which are expected to become more frequent with progressing climate change.

Recent meta-analyses suggest risks of increased nitrate leaching with the implementation of reduced tillage practices. This study aimed to quantify effects of a subsidized and commonly implemented form of non-inversion tillage in Switzerland (NIT, i.e. chisel ploughing) in comparison to conventional tillage (CT, i.e. mouldboard ploughing) on nitrate leaching and its driving processes (i.e. water fluxes, soil temperature, plant uptake). A lysimeter experiment was conducted at the lysimeter facility Reckenholz/Zurich in Switzerland, mimicking tillage differences. Results after three years of treatment implementation show that during the following three years, cumulative nitrate leaching was 26 % higher under CT than under NIT (i.e. 63 ± 10 kg/ha N with CT vs. 46 ± 9 kg/ha N with NIT). The observed effect was driven by differences in nitrate concentrations in seepage water rather than seepage water amounts. The beneficial effect of NIT on nitrate leaching was most pronounced during and shortly after a bare soil period following sugar beet cultivation, which coincided with above-average spring precipitation. These findings suggest that reduced soil management may hold the potential to reduce nitrate leaching during winter and spring wet spells with poor plant cover, which are expected to become more frequent with progressing climate change.

The world’s growing population raises concerns about future food security. At the same time, environmental challenges such as climate change, biodiversity loss, and the depletion of natural resources must be addressed, calling for a transformation of agriculture. This need is exacerbated by the limited availability of land suitable for arable farming. In this study, we examined the potential of agricultural land for arable farming and grassland use in Switzerland, under the premise that agricultural land use should align with the biophysical and environmental capacity of each location. In an iterative co-design process with scientists and public authorities, we elaborated three scenarios for agricultural transformation, which progressively incorporated (i) biophysical constraints (soil, climate, and topography) and (ii) environmental constraints (soil loss and eutrophication due to risk of erosion), as well as (iii) greenhouse gas emissions from drained organic soils. Our results show that the allocation of 40% arable land and 60% grassland in the most restrictive scenario closely resembles the current distribution (46% and 54%), respectively. However, the scenarios also revealed significant spatial shifts between arable land and grassland at the local level: only two-thirds of today’s arable land areas match their natural site conditions. Evidence from this study underscores the critical importance of site-adapted transitions of agricultural land use and the need for site-adapted management alternatives for farmland presently assigned to inadequate land use. Overall, this research provides a novel contribution by allowing the identification of hotspot areas for agricultural transformation at the local scale. We show that these site-specific land use analyses are essential for guiding effective land use planning and policy advice that strengthen the integrity of environmental performance and agricultural productivity, and support the development of targeted and sustainable land use strategies.

Recent meta-analyses suggest risks of increased nitrate leaching with the implementation of reduced tillage practices. This study aimed to quantify effects of a subsidized and commonly implemented form of non-inversion tillage in Switzerland (NIT, i.e. chisel ploughing) in comparison to conventional tillage (CT, i.e. mouldboard ploughing) on nitrate leaching and its driving processes (i.e. water fluxes, soil temperature, plant uptake). A lysimeter experiment was conducted at the lysimeter facility Reckenholz/Zurich in Switzerland, mimicking tillage differences. Results after three years of treatment implementation show that during the following three years, cumulative nitrate leaching was 26 % higher under CT than under NIT (i.e. 63 ± 10 kg/ha N with CT vs. 46 ± 9 kg/ha N with NIT). The observed effect was driven by differences in nitrate concentrations in seepage water rather than seepage water amounts. The beneficial effect of NIT on nitrate leaching was most pronounced during and shortly after a bare soil period following sugar beet cultivation, which coincided with above-average spring precipitation. These findings suggest that reduced soil management may hold the potential to reduce nitrate leaching during winter and spring wet spells with poor plant cover, which are expected to become more frequent with progressing climate change.