| 1. |
- Fukumasu, Jumpei, et al.
(författare)
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Oxalate-extractable aluminum alongside carbon inputs may be a major determinant for organic carbon content in agricultural topsoils in humid continental climate
- 2021
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Ingår i: Geoderma. - : Elsevier BV. - 0016-7061 .- 1872-6259. ; 402
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Tidskriftsartikel (refereegranskat)abstract
- The relative importance of various soil mineral constituents (e.g. clay-sized particles, aluminum- and iron-bearing mineral reactive phases) in protecting soil organic carbon (SOC) from decomposition is not yet fully understood in arable soils formed from quaternary deposits in humid continental climates. In this study, we investigated the relationships between soil physico-chemical properties (i.e. contents of oxalate-extractable aluminum (Alox) and iron (Feox) and clay size particle < 2 mu m), grain yield (as a proxy for carbon input) and total SOC as well as SOC in different soil fractions for samples taken from the topsoil of an arable field at Bjertorp in south-west Sweden. We found a positive correlation between Alox and total SOC content, where Alox explained ca. 48% of the spatial variation in SOC. We also found that ca. 80% of SOC was stored in silt- and claysized (SC) fractions, where Al-bearing reactive mineral phases (estimated by Alox) may be important for organicmineral associations and clay aggregation. Our results were supported by data collated from the literature for arable topsoil in similar climates, which also showed positive correlations between SOC and Alox contents (R-2 = 23.1 - 74.5%). Multiple linear regression showed that including spatially-variable crop yields as a proxy for carbon inputs improved the prediction of SOC variation across the Bjertorp field. Other unquantified soil properties such as exchangeable calcium may account for the remaining unexplained variation in topsoil SOC. We conclude that Al-bearing reactive mineral phases are more important than clay content and Fe-bearing reactive mineral phases for SOC stabilization in arable topsoil in humid continental climates.
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| 2. |
- Koestel, Johannes, et al.
(författare)
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Approaches to delineate aggregates in intact soil using X-ray imaging
- 2021
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Ingår i: Geoderma. - : Elsevier BV. - 0016-7061 .- 1872-6259. ; 402
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Tidskriftsartikel (refereegranskat)abstract
- Soil structure refers to the spatial arrangement of primary soil particles and pores, and is known to influence a variety of soil functions including carbon sequestration and water holding capacity. At present, research in this field is often divided, focusing either on pores where pore networks are investigated in undisturbed soil or on solids where isolated soil aggregates are commonly studied. The choice of approach depends on the needs and traditions in different disciplines of soil science. While there is much debate regarding how well these viewpoints relate to each other, there have been only marginal research efforts undertaken to compare them quantitatively. In this study, we presented and evaluated methods to identify 3-D subunits in X-ray images of eight undisturbed soil samples that we interpreted as macroaggregates, and compared these to to results from drop-shatter tests. Here, we exploited the cohesive forces of water that induces shrinkage cracks under drying. Despite promising trends, comparisons between image and drop-shatter test derived aggregate properties remained inconclusive. Nevertheless, our results encourage further investigations on larger sample sets and different observation scales. The here presented and discussed aggregate delineation methods illustrate an approach to harmonize soil structure characterization in terms of both pore-networks and soil aggregation. For example, respective extended approaches may be developed to evaluate the locations of microaggregates within macroaggregates.
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| 3. |
- Messing, Ingmar, et al.
(författare)
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Soil particle size distribution – comparison between laser diffraction, integral suspension pressure and sedimentation (pipette) methods
- 2021
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- <p>The sedimentation (pipette) (SP) method has been in use for a long time as a solid reference method to estimate particle size distribution (PSD) in soil. The procedure is demanding, not the least concerning the manual extraction of soil fractions at given depth and time intervals during the sedimentation process and their subsequent drying and weighing. The more recent laser diffraction (LD) and integral suspension pressure (ISP) methods are promising alternatives. They have the advantage that the extraction-drying-weighing procedure for the finer soil fractions (clay and silt) is replaced by automatic registration of particle volumes (for LD) and pressures at given depth during the sedimentation process (for ISP). Due to these differences in measurement technics, PSD:s determined with LD and ISP methods often deviate more or less from PSD:s by SP method, which have implications for the matching with historical SP soil databases. We present some draft results of studies comparing the three methods on samples from agricultural soils in Sweden. The results show that there is still a need for further fine-tuning in the methodologies to align PSD composition from one method to the other.</p>
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| 4. |
- Messing, Ingmar, et al.
(författare)
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Variability and compatibility in determining soil particle size distribution by sieving, sedimentation and laser diffraction methods
- 2024
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Ingår i: Soil and Tillage Research. - 0167-1987 .- 1879-3444. ; 238
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Tidskriftsartikel (refereegranskat)abstract
- A range of methods and applications are in use to determine soil particle size distribution. Due to the differences in measurement technology, the analytical results may deviate more or less from each other, which has implications for the matching with historical soil databases. There is a need for studies to critically evaluate their results, both concerning subsample variabilities and compatibilities. In the present study the more recent integral suspension pressure (ISP) and laser diffraction (LDM) methods were compared with the reference sieve and pipette (SPM) method. Samples from topsoil and subsoil of four agricultural soils with sandy clay loam to clay textures were analyzed. A protocol, comparing alternative pre-sievings at the meshes 0.063 (ps0.063), 0.2 (ps0.2) and 2.0 mm (ps2) for the sedimentation (SPM, ISP) and laser diffraction (LDM) measurements, was used. Here we report, based on particle size fraction contents for clay (<0.002 mm), silt (0.002–0.063 mm) and sand (0.063–2.0 mm), i) apparent deviations between pre-sieving options for each method, ii) variabilities between sample replicates (three subsamples), and iii) relationships (linear regression) and iv) texture class differences between SPM, ISP and LDM analyses. Overall, SPM showed smallest deviations between pre-sieving options, LDM largest, and ISP intermediate. Higher silt content, for ISP, and higher sand content, for LDM, seemed to be critical in the choice of optimum pre-sieving. Regarding variabilities between replicates, SPM showed smallest variabilities, ISP (especially ISP-ps0.2 and ISP-ps2) and LDM-ps2 largest, and LDM-ps0.063 and LDM-ps0.2 intermediate. SPM-ps0.063, SPM-ps2, ISP-ps2 and ISP-ps0.2 showed strongest relationships (i.e. largest R2 ) with the reference SPM-ps0.2, LDM-ps0.063 intermediate and LDM-ps2 weakest. Regarding texture classification, compared to the reference SPM-ps0.2, SPM-ps2 and ISP-ps2 showed largest (good, i.e. 80–100% of the cases) agreement, whereas LDM pre-sievings showed smallest (LDM-ps0.063, poor agreement, i.e. <55%). Lineartransfer transformed LDMt-ps0.063 improved the texture compatibility with SPM-ps0.2 to intermediate (63%) agreement, and SPMt-ps0.063 and ISPt-ps0.2 from intermediate (75%) to good (88%) agreement. Also clay-silt cutoff modified LDMc-ps0.063 and LDMc-ps0.2 improved the texture compatibility with SPM-ps0.2, to intermediate (63%) agreement. There is a need to continue fine-tuning methodologies to align particle size distribution composition from one method to the other, especially regarding the influence of equivalent and efficient particle shape and pre-treatment procedures on the results.
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| 5. |
- Meurer, Katharina, et al.
(författare)
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Modelling dynamic interactions between soil structure and the storage and turnover of soil organic matter
- 2020
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 17, s. 5025-5042
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Tidskriftsartikel (refereegranskat)abstract
- Models of soil organic carbon (SOC) storage and turnover can be useful tools to analyse the effects of soil and crop management practices and climate change on soil organic carbon stocks. The aggregated structure of soil is known to protect SOC from decomposition and, thus, influence the potential for long-term sequestration. In turn, the turnover and storage of SOC affects soil aggregation, physical and hydraulic properties and the productive capacity of soil. These two-way interactions have not yet been explicitly considered in modelling approaches. In this study, we present and describe a new model of the dynamic feedbacks between soil organic matter (SOM) storage and soil physical properties (porosity, pore size distribution, bulk density and layer thickness). A sensitivity analysis was first performed to understand the behaviour of the model. The identifiability of model parameters was then investigated by calibrating the model against a synthetic data set. This analysis revealed that it would not be possible to unequivocally estimate all of the model parameters from the kind of data usually available in field trials. Based on this information, the model was tested against measurements of bulk density, SOC concentration and limited data on soil water retention and soil surface elevation made during 63 years in a field trial located near Uppsala (Sweden) in three treatments with different organic matter (OM) inputs (bare fallow, animal and green manure). The model was able to accurately reproduce the changes in SOC, soil bulk density and surface elevation observed in the field as well as soil water retention curves measured at the end of the experimental period in 2019 in two of the treatments. Treatment-specific variations in SOC dynamics caused by differences in OM input quality could be simulated very well by modifying the value for the OM retention coefficient epsilon (0.37 for animal manure and 0.14 for green manure). The model approach presented here may prove useful for management purposes, for example, in an analysis of carbon sequestration or soil degradation under land use and climate change.
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| 6. |
- Nimblad Svensson, David, et al.
(författare)
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An investigation in laser diffraction soil particle size distribution analysis to obtain compatible results with sieve and pipette method
- 2022
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Ingår i: Soil and Tillage Research. - : Elsevier BV. - 0167-1987 .- 1879-3444. ; 223
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Tidskriftsartikel (refereegranskat)abstract
- Recent studies have shown that soil particle size analyses using laser diffraction method (LDM) can give compatible results compared with traditional sedimentation based methods, if the clay-silt particle size cutoff is transformed. Additionally, procedures including separation of the sand fraction by wet sieving and running a well dispersed sample of only fractions smaller than sand during laser diffraction measurement, have given promising results. The main purpose of the present study was to test a combination of these approaches for determining cutoff transformed LDM values on 44 soil samples from agricultural sites spread over Sweden, including its compatibility with the sieve and pipette method (SPM). Furthermore, these results were compared with results of transformed LDM values based on pedotransfer functions between measured LDM and SPM. Also LDM related aspects concerning scattering parameters, repeatability and organic matter calculations were studied. To find the optimum clay-silt cutoff, Lin's concordance correlation coefficient (Lin's CCC) was calculated. The highest value (0.977) was found with the 3.409-3.905 mu m bin (a refractive index of 1.52 and an absorption coefficient of 0.1 was used). The pedotransfer-transformed LDM approach showed equally high Lin acute accent s CCC as the cutoff-transformed approach for the different soil particle fraction size classes. With the cutofftransformed LDM approach, 36 out of 44 samples were assigned to the same texture class as SPM, and with the pedotransfer-transformed LDM, the corresponding number was similar (34 out of 44 samples). The results here are promising for application in routine soil analyses, but more specific transformed clay-silt cutoffs and pedotransfer functions for LDM versus SPM should ideally be established for different types of soils. For this, microscopy and image analysis methods to help understand and quantify the influence of particle shapes on obtained particle size distributions are useful.
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