Agroscope Research Station ART

Zürich, Switzerland

Agroscope Research Station ART

Zürich, Switzerland

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Regnier P.,Free University of Colombia | Friedlingstein P.,University of Exeter | Ciais P.,French Climate and Environment Sciences Laboratory | Mackenzie F.T.,University of Hawaii at Manoa | And 27 more authors.
Nature Geoscience | Year: 2013

A substantial amount of the atmospheric carbon taken up on land through photosynthesis and chemical weathering is transported laterally along the aquatic continuum from upland terrestrial ecosystems to the ocean. So far, global carbon budget estimates have implicitly assumed that the transformation and lateral transport of carbon along this aquatic continuum has remained unchanged since pre-industrial times. A synthesis of published work reveals the magnitude of present-day lateral carbon fluxes from land to ocean, and the extent to which human activities have altered these fluxes. We show that anthropogenic perturbation may have increased the flux of carbon to inland waters by as much as 1.0 Pg C yr -1 since pre-industrial times, mainly owing to enhanced carbon export from soils. Most of this additional carbon input to upstream rivers is either emitted back to the atmosphere as carbon dioxide (∼0.4 Pg C yr -1) or sequestered in sediments (∼0.5 Pg C yr -1) along the continuum of freshwater bodies, estuaries and coastal waters, leaving only a perturbation carbon input of ∼0.1 Pg C yr -1 to the open ocean. According to our analysis, terrestrial ecosystems store ∼0.9 Pg C yr -1 at present, which is in agreement with results from forest inventories but significantly differs from the figure of 1.5 Pg C yr -1 previously estimated when ignoring changes in lateral carbon fluxes. We suggest that carbon fluxes along the land-ocean aquatic continuum need to be included in global carbon dioxide budgets.


Stampfli A.,University of Bern | Fuhrer J.,Agroscope Research Station ART
Oecologia | Year: 2010

Interpretation of observations from manipulative experiments is often complicated by a multitude of uncontrolled processes operating at various spatial and temporal scales. As such processes may differ among experimental plots there is a risk that effects of experimental treatments are confounded. Here we report on a free-air ozone-exposure experiment in permanent semi-natural grassland that suggested strong ozone effects on community productivity after 5 years. We tested ozone effects and investigated the potential of confounding due to changes in nutrient management. Repeated-measure ANOVA revealed mainly negative temporal trends for frequency of abundant productive plant species. Constrained ordination additionally showed converging trajectories of species compositions for ozone and control treatments with time. Yields sampled prior to the start of the experiment and soil nitrogen concentrations revealed that spatial heterogeneity in the soil nutrient status was not accounted for by the random allocation of treatments to plots with a bias towards less productive patches in the elevated-ozone plots. Re-analysis of yield data using repeated-measure ANOVA with a covariable to account for productivity prior to the start of fumigation revealed effects on the temporal changes in total yield and yield of legumes that cannot be separated between ozone and pre-treatment nutrient status. Changes in species composition favour an ecological interpretation with spatial heterogeneity as the major cause of different yield declines. Although elevated ozone may cause subtle physiological changes with longer term implications, our new results suggest that species-rich mature grassland such as the one studied at Le Mouret may be less sensitive to elevated ozone than previously assumed. In this experiment a confounded design was hidden at the start by transitory effects of a prior change in nutrient treatments. © Springer-Verlag 2009.


Arvidsson J.,Swedish University of Agricultural Sciences | Westlin H.,Swedish Institute of Agricultural and Environmental Engineering | Keller T.,Swedish University of Agricultural Sciences | Keller T.,Agroscope Research Station ART | Gilbertsson M.,Swedish Institute of Agricultural and Environmental Engineering
Soil and Tillage Research | Year: 2011

Traditionally, tractors have been built either for tracks or wheels, with tracks mainly on heavy tractors with high power. Today, it is possible to retrofit four separate track units on a conventional agricultural tractor, creating interesting possibilities for agriculture. The objective of the present study was to compare soil compaction and traction for tracks, single and dual wheels mounted on the same tractor type. Measurements were made on two clay soils (Eutric Cambisols) in Sweden in 2009, using an 85kW tractor with a total weight of 7700kg. The rubber track system consisted of four tracks mounted on the conventional wheel axles of the tractor. The measured stresses were similar for the tracks and dual wheels at all depths studied (15, 30 and 50cm), but were considerably higher for the single wheels at all depths. Simulations of soil stresses correlated closely to measured values for the tracks and the dual wheels, but underestimated soil stresses in the topsoil compared to measured values for the single wheel. Bulk density and penetration resistance were consistently highest and saturated hydraulic conductivity lowest after wheeling with single wheels, while there were no statistically significant differences between tracks and dual wheels. With single wheels and the tractor loaded, saturated hydraulic conductivity decreased to 0.01mh-1 from 0.13mh-1 in the control, while bulk density increased from 1.24 to 1.36Mgm-3. The stress distribution in the driving direction was relatively even along the front and rear tracks, which is an advantage compared with a long single track, which often has an uneven longitudinal stress distribution. Slip was significantly higher for the dual and single wheels compared with tracks. To utilise the large contact area of the tracks, the tractor should have a low weight in relation to the engine power. © 2011 Elsevier B.V.


Berisso F.E.,University of Aarhus | Schjonning P.,University of Aarhus | Lamande M.,University of Aarhus | Weisskopf P.,Agroscope Research Station ART | And 3 more authors.
Soil and Tillage Research | Year: 2013

This study investigated the impact of vehicle traffic on soil physical properties by systematically collecting samples in a transect running from the centreline to the outside of the wheel rut in a wheeling experiment conducted on a clay loam soil at Suberg near Bern, Switzerland, in 2010. Four repeated wheelings were performed by a forage harvester (wheel load 6100kg; tyre width 80cm). Mean normal and horizontal stresses were measured with Bolling probes (at 10, 20 and 40cm depth) and load cells (at 40, 50, 60cm lateral distance from the centreline of the wheel rut at 10, 30 and 50cm depth), respectively. Intact soil cores of 100cm3 sampled at 10, 30 and 50cm depth in a soil transcet running from the centreline of the wheel rut to the unwheeled part of the field were used for measurements of water retention and air permeability (ka) at -30, -100 and -300hPa matric potential. The complete stress state in the soil profile beneath the harvester tyre was calculated using the SoilFlex model. Pore continuity index (N) and blocked air-filled porosity (εb) were estimated from the relationship between ka and air-filled porosity (εa) for a range of matric potentials. Calculated and measured stresses agreed well at all depths. At -100hPa, εa was consistently lower under the centreline of the wheel rut than at the lateral edge of the rut or outside the wheel rut, while ka was lowest at the lateral edge of the wheel rut and highest outside the wheel rut, with intermediate values under the centreline of the wheel rut. Simulations of the stress field in the soil beneath the tyre indicated that the trends in ka were determined by both the mean normal stress and the shear stress, while the trend in εa was determined by the mean normal stress only. At 10cm depth, the index of pore continuity (N) supported the interpretation that soil pores under the centreline of the wheel rut are primarily reduced in size, while pore continuity is highly affected at the lateral edge of the wheel rut, as indicated by a higher value of εb than in other locations. These results indicate that sampling along the wheel track transect can provide better information about traffic-induced changes on soil physical properties than random sampling in lateral locations relative to the centreline of the wheel rut. © 2013 Elsevier B.V.


Berisso F.E.,University of Aarhus | Schjonning P.,University of Aarhus | Keller T.,Agroscope Research Station ART | Keller T.,Swedish University of Agricultural Sciences | And 6 more authors.
Geoderma | Year: 2013

Anisotropy of soil pore functions significantly affects the transport of gas and water in soil. This paper quantifies anisotropy of subsoil pores and investigates the long-term impact of soil compaction by agricultural machinery. Two long-term field experiments on soil compaction formed the basis for the investigation, one established in 1981 on a clay soil in Finland (60°49'N, 23°23'E) and another in 1995 on a sandy clay loam in Sweden (55°49'N, 13°11'E). In 2009/2010, soil cores were sampled in vertical and horizontal directions from 0.3, 0.5, 0.7 and 0.9. m depth (the two lower depths only in Sweden). In the laboratory, water content, air-filled porosity (εa), air permeability (ka) and gas diffusivity (Ds/D0) were determined at selected matric potentials. For the sandy clay loam, morphological characteristics of pores (effective pore diameter, dB; tortuosity, τ; the number of effective pores per unit area, nB) were calculated using a tortuous tube model at - 100. hPa matric potential. Blocked air-filled porosity (εb) and a pore continuity index (N) were estimated from the relationship between ka and εa for a range of matric potentials. A factor of anisotropy (FA) was determined as the ratio of a given property measured in the horizontal direction to that in the vertical direction. ka showed anisotropic behaviour (FA<1) for the clay soil and for the 0.3. m depth of the non-compacted sandy clay loam soil, while Ds/D0 displayed anisotropy for the clay soil (FA<1). In the sandy clay loam soil, dB and nB displayed significant anisotropy (FA<1) except at 0.9. m. We interpreted this as effects of biological activities and physical processes in the B-horizon not being active in the C-horizon (0.9. m depth). Compaction generally reduced ka, Ds/D0, dB, nB and increased τ for both sampling directions. Compaction had an effect on anisotropy for soil drained to -100. hPa, but only for ka and dB in the sandy clay loam at 0.3. m depth. Compaction reduced anisotropy for the N parameter, i.e. effects on soil pore continuity at the macropore scale, while it increased the anisotropy for εb. Our data thus indicate that compaction had persistent effect on soil physical properties and also affects anisotropy, especially that of macropores. © 2012 Elsevier B.V.


Etana A.,Swedish University of Agricultural Sciences | Larsbo M.,Swedish University of Agricultural Sciences | Keller T.,Swedish University of Agricultural Sciences | Keller T.,Agroscope Research Station ART | And 4 more authors.
Geoderma | Year: 2013

Persistence of subsoil compaction was investigated in a field experiment in southern Sweden. The investigation compared two treatments (control and compaction by four passes track-by-track), 14 years after the experimental traffic. The compaction experiment was carried out in 1995 with a 6-row sugar beet harvester with a wheel load of c. 10.4 Mg. Investigations included penetration resistance, bulk density, water retention, saturated hydraulic conductivity, in situ near-saturated hydraulic conductivity, and dye tracing experiments. The measurements of penetration resistance and bulk density clearly showed the persistence of subsoil compaction. In addition, both macroporosity and saturated and near-saturated hydraulic conductivity were smaller in the compacted plots, although these differences were not statistically significant. Dye tracing allowed us to visualize flow patterns in the soil and to quantitatively distinguish compacted and noncompacted subsoil profiles. Despite significant soil textural heterogeneity across the experimental field, the dye tracing data showed that persistent compaction may enhance preferential flow. © 2012 Elsevier B.V.


Berisso F.E.,University of Aarhus | Schjonning P.,University of Aarhus | Keller T.,Swedish University of Agricultural Sciences | Keller T.,Agroscope Research Station ART | And 6 more authors.
Soil and Tillage Research | Year: 2012

The ever-increasing weight of agricultural machines exacerbates the risk of subsoil compaction, a condition believed to be persistent and difficult to alleviate by soil tillage and natural loosening processes. However, experimental data on the persistency of subsoil compaction effects on soil pore functioning are scarce. This study evaluated and quantified persistent effects of subsoil compaction on soil pore structure and gas transport processes using intact cores taken at 0.3, 0.5, 0.7 and 0.9m depth from a loamy soil in a compaction experiment in southern Sweden (Brahmehem Farm). The treatments included four repeated wheelings with ~10Mg wheel loads. Water retention characteristics (WRC), air permeability (k a) and gas diffusivity (D s/D o) were measured. A dual-porosity model fitted the WRC well, and there was a reduction in the volume of macropores >30μm in compacted compared with control soil for all soil depths. Averaged for all sampling depths and also for some individual depths, both k a and D s/D o were significantly reduced by compaction. Gas transport measurements showed that the experimental soil was poorly aerated, with local anoxic conditions at water regimes around field capacity in all plots and depths, but with significantly higher percentage anoxia in compacted soil. Our main findings were that: (1) commonly used agricultural machinery can compact the soil to 0.9m depth, (2) the effect may persist for at least 14 years, and (3) important soil functions are affected. © 2012 Elsevier B.V..


Havaee S.,Isfahan University of Technology | Ayoubi S.,Isfahan University of Technology | Mosaddeghi M.R.,Isfahan University of Technology | Keller T.,Agroscope Research Station ART | Keller T.,Swedish University of Agricultural Sciences
Soil Use and Management | Year: 2014

This study was conducted to investigate the impact of land use (dryland farming, grassland and irrigated farming) on bulk density, (ρb) and relative bulk density (ρb-rel), and to study the relationships between ρb and ρb-rel, respectively, and soil organic matter content (OM) and soil texture at 100 locations in calcareous soils of central Iran. The ρb-rel was expressed as the ratio of ρb to a reference bulk density, ρbef. By considering ρb-ref an inherent soil property that is dependent on soil texture but not on OM, the combined effects of OM due to land use and compaction (due to agricultural machinery) on the degree of compactness could be explored. Multiple linear regression was used to derive pedotransfer functions for predicting ρb and ρb-rel. It was found that ρb-rel is strongly affected by OM, and a strong correlation was obtained between ρb-rel and the ratio of OM to clay content. The predictive performance of the multiple regression models was poorest for irrigated farming, which might be explained by intensive soil disturbance by tillage in irrigated farming. The main effect of land use was on OM, and consequently, the degree of compactness was mainly controlled by OM. The greatest OM and least ρb-rel were measured in irrigated farming. Dryland farming had the least OM and the greatest ρb-rel. © 2013 British Society of Soil Science.


Leifeld J.,Agroscope Research Station ART | Gubler L.,University of Bern | Grunig A.,Agroscope Research Station ART
Plant and Soil | Year: 2011

Peatlands act as CO2 sinks that store more soil carbon per unit area than any other ecosystem. Increased aeration and subsequent oxidation following drainage causes peatlands to lose carbon and leads to a relative increase in the concentration of inorganic compounds. To infer carbon losses as a result of drainage, we studied four sites in Central Europe with different drainage states and land-use histories. We used differences in ash content of both catotelm peat and near-surface layers as well as the results of soil carbon inventories. The method yielded reasonable results, at least for two drained sites, where the mean loss rates varied between 0. 14 and 0. 49 kg C m-2 a-1. Comparison with a pristine bog showed that a relative increase of ash content is not unique to drained sites and that previous land management also affected natural peatlands with concomitant losses similar in magnitude to their drained counterparts. Rehabilitation of a previously drained site dissipated the original ash peak profile. In conclusion, the method is suitable for predicting carbon losses from ombrotrophic bogs under certain conditions but in countries with a long-lasting tradition of anthropogenic interference it is impossible to attribute drainage as the only factor governing relative increases in ash content in ombrotrophic peatlands. © 2010 Springer Science+Business Media B.V.


Arvidsson J.,Swedish University of Agricultural Sciences | Keller T.,Swedish University of Agricultural Sciences | Keller T.,Agroscope Research Station ART
Soil and Tillage Research | Year: 2011

Models for draught requirement are in most cases developed from foundation engineering, and generally include cohesion as the main parameter to define soil strength. There are also empirical models which include penetration resistance as a soil strength factor. This study examined specific draught during mouldboard ploughing as a function of soil strength and related the results to existing models. Draught requirement was measured on 37 different occasions at 15 sites with clay content ranging from 13 to 56%. Four of these sites were ploughed on several occasions in the autumn to obtain a range of water contents. Shear vane measurements were carried out on all occasions and were used to derive soil cohesion. Penetration resistance was measured on 21 occasions. Soil strength proved much more sensitive to changes in water content than draught requirement. Consequently, model predictions of specific draught were much higher than measured values in soil with high cohesion values. A possible explanation is that specific draught mainly depends on inter-aggregate strength, while the intra-aggregate strength may be considerably higher. Over all tillage occasions, specific draught was much more strongly correlated to cohesion than to penetration resistance. There was also a clear correlation between draught and soil clay content. Multiple regression including cohesion and soil water content resulted in a much higher coefficient of determination than regression with cohesion only. The results indicate that neither shear vane nor penetrometer measurements are sufficient to predict draught requirement, and it is desirable to develop a simple yet reliable field method that can be used for this purpose. More general estimates of fuel consumption can probably be made based on the soil clay content only. © 2010 Elsevier B.V.

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