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| 2. |
- Meurer, Katharina, et al.
(författare)
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A framework for modelling soil structure dynamics induced by biological activity
- 2020
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 26, s. 5382-5403
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Tidskriftsartikel (refereegranskat)abstract
- Soil degradation is a worsening global phenomenon driven by socio-economic pressures, poor land management practices and climate change. A deterioration of soil structure at timescales ranging from seconds to centuries is implicated in most forms of soil degradation including the depletion of nutrients and organic matter, erosion and compaction. New soil-crop models that could account for soil structure dynamics at decadal to centennial timescales would provide insights into the relative importance of the various underlying physical (e.g. tillage, traffic compaction, swell/shrink and freeze/thaw) and biological (e.g. plant root growth, soil microbial and faunal activity) mechanisms, their impacts on soil hydrological processes and plant growth, as well as the relevant timescales of soil degradation and recovery. However, the development of such a model remains a challenge due to the enormous complexity of the interactions in the soil-plant system. In this paper, we focus on the impacts of biological processes on soil structure dynamics, especially the growth of plant roots and the activity of soil fauna and microorganisms. We first define what we mean by soil structure and then review current understanding of how these biological agents impact soil structure. We then develop a new framework for modelling soil structure dynamics, which is designed to be compatible with soil-crop models that operate at the soil profile scale and for long temporal scales (i.e. decades, centuries). We illustrate the modelling concept with a case study on the role of root growth and earthworm bioturbation in restoring the structure of a severely compacted soil.
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| 3. |
- Moberg, Emma, et al.
(författare)
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Effect of ley inclusion in crop rotations on soil carbon stocks in a life cycle perspective
- 2022
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Carbon sequestration in agricultural soils has been proposed as an important climate change mitigation strategy. Carbon stocks in soils can be increased by different cropland management options, one of which is greater inclusion of perennial crops in crop rotations. This study compared the climate impact in a life cycle perspective of continuous ley-dominated rotations and continuous cereal rotations at two different sites (loam, clay) in Sweden. Effects of these systems on carbon content in topsoil and subsoil over 35 years were assessed based on data from two ongoing longterm field trials. The continuous cereal rotations led to a decrease in soil organic carbon stocks at both sites, resulting in an increase in overall climate impact of 8-19%. The ley-dominated rotationsincreased soil organic carbon stocks at both sites over time, contributing to a decrease in overall climate impact of 7% (clay) and 18% (loam). The high soil carbon accumulation in the ley rotation at the site with loamy soil, where soil carbon stocks increased in both topsoil and subsoil, waspossibly due to more roots entering the subsoil than at the site with clay soil.
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| 4. |
- Parvin, Nargish, et al.
(författare)
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On the relationships between the size of agricultural machinery, soil quality and net revenues for farmers and society
- 2022
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Ingår i: Soil Security. - : Elsevier. - 2667-0062. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Mechanization in agriculture has greatly improved the efficiency of field operations, but also resulted in heavier agricultural vehicles, which has led to increased risks of soil compaction. Hence, farmers benefit from machinery with higher capacity but may suffer from decreased yields caused by compaction. Compaction may result in further environmental costs to society. We present a framework that relates the machinery capacity to soil compaction and its impacts on crop yields and environmental disservices, and associated revenues and costs for farmers and society. We combined simulations using a soil compaction model and a soil-crop model with simple economic analyses. We applied the framework to a case study of cereal production in Sweden, to derive the optimal combine harvester size that maximizes the farmer's private profit and the societal net benefit, respectively. Increased machinery size decreased harvesting costs, but also reduced simulated crop yields and thus crop revenue as a result of soil compaction. Furthermore, in the model simulations, compaction also increased surface run-off, nitrogen leaching and greenhouse gas emissions. Intermediate machinery size maximized the farmer's net revenue. Net benefits for society were highest for the lowest possible compaction level, due to the considerable external costs from soil compaction. We show that the optimal machinery size and thus compaction level for maximum farmer revenue would decrease if either producer prices were higher, harvesting costs savings from larger machinery were smaller, or if farmers were charged for (part of the) environmental costs.
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| 5. |
- Parvin, Nargish, et al.
(författare)
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Seedbed consolidation and surface sealing for soils of different texture and soil organic carbon contents
- 2021
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Ingår i: Soil and Tillage Research. - : Elsevier BV. - 0167-1987 .- 1879-3444. ; 206
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Tidskriftsartikel (refereegranskat)abstract
- The soil structure near the surface of agricultural soils changes with season mainly by land management together with climatic and biological factors. Quantitative analysis of post-tillage changes in soil structure and related hydraulic properties are necessary for evaluating and improving models of soil hydrological and transport processes. The objectives of this study were to quantify changes in soil seedbed structure induced by rainfall and drainage and to estimate the eff ;ects of soil texture and SOC on these changes. We collected samples from the harrowed layer of twenty-six fine to coarse textured Swedish mineral soils. Air-dried soil was placed in cylinders (5 cm high, diameter 5 cm) and exposed to simulated rainfall (5 mm h(-1) for 4 h) and drainage (-50 cm pressure potential) cycles in the laboratory. We used X-ray tomography to quantify changes in pore networks in a thin surface layer and in the whole cylinder. Infiltration rates at-5 cm pressure potential were measured using a mini disc tension infiltrometer on replicate air-dried samples and on the samples included in the consolidation experiments at the final state. Total imaged specific pore volumes generally decreased from initial to final state and pore size distributions were shifted towards larger proportions of below image resolution pores (< 80 mu m). There was a strong positive correlation between clay content and changes (i.e. final state-initial state) in the specific volume of pores <80 mu m. Soils with high clay content and soil organic carbon (SOC) content often have strong aggregates that resist changes. Nevertheless, both clay and SOC contents were negatively correlated with the changes in specific imaged pore volume. These results highlight the importance of swelling, which is largely controlled by clay content, for seedbed consolidation. In line with previous studies, when excluding coarse textured soil, the changes in surface porosity were negatively correlated with silt content. Changes in infiltration capacity were not significantly correlated with any basic soil properties. Our results suggest that shrinking swelling should be a central part in any model for seedbed consolidation.
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| 6. |
- Sierra, Carlos, et al.
(författare)
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Carbon sequestration in the subsoil and the time required to stabilize carbon for climate change mitigation
- 2024
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Ingår i: Global Change Biology. - 1354-1013 .- 1365-2486. ; 30
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Forskningsöversikt (refereegranskat)abstract
- Soils store large quantities of carbon in the subsoil (below 0.2 m depth) that is generally old and believed to be stabilized over centuries to millennia, which suggests that subsoil carbon sequestration (CS) can be used as a strategy for climate change mitigation. In this article, we review the main biophysical processes that contribute to carbon storage in subsoil and the main mathematical models used to represent these processes. Our guiding objective is to review whether a process understanding of soil carbon movement in the vertical profile can help us to assess carbon storage and persistence at timescales relevant for climate change mitigation. Bioturbation, liquid phase transport, belowground carbon inputs, mineral association, and microbial activity are the main processes contributing to the formation of soil carbon profiles, and these processes are represented in models using the diffusion-advection-reaction paradigm. Based on simulation examples and measurements from carbon and radiocarbon profiles across biomes, we found that advective and diffusive transport may only play a secondary role in the formation of soil carbon profiles. The difference between vertical root inputs and decomposition seems to play a primary role in determining the shape of carbon change with depth. Using the transit time of carbon to assess the timescales of carbon storage of new inputs, we show that only small quantities of new carbon inputs travel through the profile and can be stabilized for time horizons longer than 50 years, implying that activities that promote CS in the subsoil must take into consideration the very small quantities that can be stabilized in the long term.We reviewed mathematical models that represent soil carbon dynamics with depth and found thatmost models adopt the diffusion, advection, reaction (decomposition) paradigm. Transport processes play a secondary role in shaping soil carbon profiles, with the difference betweencarbon inputs and decomposition (g) playing a major role. Carbon stocks in the subsoil can be increased by decreasing the rate of change of soil carbon withdepth, increasing vertical transport (v) or decreasing g.image
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