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Guy Richard - One of the best experts on this subject based on the ideXlab platform.
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Role of earthworms in regenerating soil structure after compaction in reduced tillage systems
Soil Biology and Biochemistry, 2012Co-Authors: Yvan Capowiez, Guy Richard, Samartino Stéphane, Cadoux Stéphane, Bouchant Pierre, Boizard HubertAbstract:New non-tillage or reduced tillage agricultural practises are being increasingly adopted but generally result in higher soil compaction. Due to their recognised physical influence mainly through burrow creation, it is often claimed that earthworm activity could alleviate soil compaction in these systems. To put this assumption to the test, an experimental compaction event was carried out on one plot of arable land. The abundance and biomass of earthworms were evaluated in compacted (under Wheel Tracks) and non-compacted (between Wheel Tracks) zones, seven times over a two-year period. In addition, the functional consequences of earthworm activity, defined by burrow abundance assessed in 2D and 3D and water infiltration, were measured three times over the same period. The short-term (less than three months) effects of the compaction were clear: soil bulk density increased from 1.46 to 1.57 g cm À3 , the abundance and biomass of earthworms were greatly reduced (À40% and À70% respectively) and the number and continuity of macroporosity were lower under Wheel Tracks at least until a depth of 30 cm. After these initial detrimental effects, we observed a rapid recovery of earthworm populations with no statistical difference between compacted and control zones more than three months after the compaction. However, the recovery of soil functional properties linked to earthworm activity, macro-porosity and water infiltration, was much slower and took between 12 and 24 months. Despite these modifications, there were no significant changes in soil bulk density with time during the two-year period. This study demonstrates that earthworms are important actors in the regeneration of com-pacted soil. Although the complete regeneration of compacted soil by earthworms is a slow process, agricultural practises that promote earthworm density and activity should be encouraged in reduced or minimum tillage systems.
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Experimental evidence for the role of earthworms in compacted soil regeneration based on field observations and results from a semi-field experiment
Soil Biology and Biochemistry, 2009Co-Authors: Yvan Capowiez, Guy Richard, Stéphane Cadoux, Pierre Bouchand, Jean Roger-estrade, Hubert BoizardAbstract:In laboratory experiments, earthworms are often observed to burrow through compacted soil layers, leading to the general assumption that these animals play a significant role in regenerating compacted soils in agricultural plots. To demonstrate this role under field conditions, the abundance of earthworm macropores inside compacted zones was estimated on plots under reduced (RT) or conventional tillage (CT). Then, different types of compacted zones typically found in CT (plough pan and compacted clods) and RT plots (compacted volume under Wheel Tracks) were experimentally simulated in wooden boxes, buried in the field and inoculated with different earthworm species. After 6 weeks of incubation, the number of macropores inside the compacted zones was examined. Field observations showed that approximately 10% and 30% of the compacted zones were colonised by at least one macropore in CT and RT plots, respectively. A significantly greater number of anecics was found in RT plots, but we could not conclude that this ecological type of earthworm plays a more major role in the regeneration process in these plots since there were fewer compacted zones and these covered a smaller area in CT. The semi-field experiment provided evidence that earthworm-mediated regeneration of compacted zones is possible and its nature varies between ecological types of earthworm. Lumbricus terrestris, which makes individual burrows that are vertical and deep, was the main species to cross through the plough pan. The other three earthworm species (Aporrectodea giardi, A. caliginosa and A. rosea) did burrow inside the other types of compacted zones (“Wheel Tracks” and “compacted clods”). In every case, however, macropore density was far greater in non-compacted zones, illustrating that avoidance of compacted soil by earthworms is important and should be taken into account when extrapolating results from laboratory studies.
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Characterisation of the structural heterogeneity of the soil tilled layer by using in situ 2D and 3D electrical resistivity measurements
Soil and Tillage Research, 2009Co-Authors: Maud Seger, Isabelle Cousin, Hubert Boizard, Anthony Frison, Guy RichardAbstract:Compaction is responsible for soil physical degradation by affecting soil structure, i.e. the arrangement of soil particles in space. Under Wheel Tracks, the soil density increases and the porosity decreases, which affects soil physical properties. Conventional methods of measuring soil compaction are time consuming, destructive and give misinterpretations by using 2D informations. We then need non-destructive tools that enable the description of the soil structure in the field at a centimetric or decimetric resolution. The aim of this study is to discuss the feasibility of using a geophysical method, the electrical resistivity one, to describe the complex 3D structure of the cultivated layer in an agricultural field. The studied zone - a 2.4 m x 1.4 m field plot - consists in a compacted band, first created by a heavy tractor, then fragmented by ploughing. 3D information about the structure was given by the analysis of ten successive morphological profiles spaced 10 cm apart. They have shown that the structure was composed by dense aggregates, loose material and large voids. The studied zone was characterised by electrical prospectings thanks to both 2D investigation (Wenner arrays of 24 electrodes) and 3D investigation (square arrays of 48 electrodes), with electrodes spaced 10 cm apart. The analysis of apparent resistivity and interpreted resistivity data has shown that we can localise zones with large voids, loose material or compacted aggregates. These results have been confirmed by direct observations on soil profiles. The 3D electrical resistivity prospecting method thus enables the description of the 3D heterogeneity of the tilled layer at a decimetric resolution and constitutes then an alternative tool to the X-ray tomography for studies in the field.
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Can electrical resistivity tomography describe soil structure evolution?
2003Co-Authors: Anatja Samouëlian, Guy Richard, Isabelle Cousin, Alain Tabbagh, Ary BruandAbstract:Variations of soil structure is significant for the understanding of water and gas transfer in soil profiles. In the context of arable land, soil structure can be compacted due to either agriculture operation (Wheel Tracks), or hardsetting and crusting processes. As a consequence, soil porosity is reduced which may lead to decrease water infiltration and to anoxic conditions. Porosity can be increased by cracks formation due to swelling and shrinking phenomenon. We present here a laboratory experiment based on soil electrical characteristics. Electrical resistivity allows a non destructive three dimensional and dynamical analysis of the soil structure. Our main objective is to detect cracks in the soil. Cracks form an electrical resistant object and the contrast of resistivity between air and soil is large enough to be detected. Our sample is an undisturbed soil block 240mm*170mm*160mm with an initial structure compacted by Wheel traffic. Successive artificial cracks are generated. Electrodes built with 2 mm ceramic cups permit a good electrical contact at the soil surface whatever its water content. They are installed 15 mm apart and the electrical resistivity is monitored using a dipole-dipole and wenner multi-electrodes 2D imaging method which gives a picture of the subsurface resistivity. The interpreted resistivity sections show the major soil structure. The electrical response changes with the cracks formation. The structure information extracted from the electrical map is in good agreement with the artificially man-made cracks. These first results demonstrate the relevance of high resolution electrical imaging of the soil profile. Further experiments need to be carried out in order to monitor natural soil structure evolution during wetting-drying cycles.
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effect of compaction on the porosity of a silty soil influence on unsaturated hydraulic properties
European Journal of Soil Science, 2001Co-Authors: Guy Richard, J F Sillon, Ary Bruand, Isabelle Cousin, J GuerifAbstract:Summary Tillage and traffic modify soil porosity and pore size distribution, leading to changes in the unsaturated hydraulic properties of the tilled layer. These changes are still difficult to characterize. We have investigated the effect of compaction on the change in the soil porosity and its consequences for water retention and hydraulic conductivity. A freshly tilled layer and a soil layer compacted by Wheel Tracks were created in a silty soil to obtain contrasting bulk densities (1.17 and 1.63 g cm−3, respectively). Soil porosity was analysed by mercury porosimetry, and scanning electron microscopy was used to distinguish between the textural pore space and the structural pore space. The laboratory method of Wind (direct evaporation) was used to measure the hydraulic properties in the tensiometric range. For water potentials < −20 kPa, the compacted layer retained more water than did the uncompacted layer, but the relation between the hydraulic conductivity and the water ratio (the volume of water per unit volume of solid phase) was not affected by the change in bulk density. Compaction did not affect the textural porosity (i.e. matrix porosity), but it created relict structural pores accessible only through the micropores of the matrix. These relict structural pores could be the reason for the change in the hydraulic properties due to compaction. They can be used as an indicator of the consequences of compaction on unsaturated hydraulic properties. The modification of the pore geometry during compaction results not only from a decrease in the volume of structural pores but also from a change in the relation between the textural pores and the remaining structural pores.
Isabelle Cousin - One of the best experts on this subject based on the ideXlab platform.
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Compaction effect on the availability of water stocks for crops
2011Co-Authors: Arlène Besson, Maud Seger, Guillaume Giot, Bernard Nicoullaud, Isabelle CousinAbstract:Soil structure can be strongly damaged by compaction which derives from compressive forces of Wheels and tillage machinery applied to soils under farming systems. Compaction process alters the spatial arrangement, size and shape of clods and aggregates. As a consequence, the soil bulk density and the soil strength increase and the soil functioning is severely disturbed with a reduction in permeability to air, water and heat which in turn affects environmental quality, root and shoot growth and consequently crop production. Compaction causes a restriction in root penetration and rooting depth, an increase in root diameter and a reduction in water and nutrient uptake. However the responses in rooting stress and then in plant growth to compaction are controversial. They depend on the degree of compaction, its depth and persistence both laterally and vertically, on the texture of soils and their capacity to transfer water and more on weather conditions. Indeed, the crop production is strongly influenced by water stocks invested by roots. It was also observed that roots are preferentially confined to macropores as earthworm’s galleries, voids, cracks, bypassing generally compacted clods with a clump effect in loose soil. For high rainfall intensity, it results in preferential water flow which may supply enough water to plants. In addition compaction damage is not irreversible. As a result of climate activity, soil cracking through wetting and drying, fauna activity, compacted clods may progressively break down with decreasing soil impedance and changing in water retention and flow. Given the above mentioned debate, the objective of this study was to examine in space and time at high resolution the eventual changes in water content and soil structure of cropped soil as compared to bare soil after a prior compaction by in-field Wheel traffic. Our study focused on the growing season of wheat crop. From in-field experiment, a precise time monitoring of water content and soil structure was analysed at the soil profile scale on a loamy-clay soil. The methods used to estimate both variables consisted in local soil sampling and visual morphological descriptions supplemented by Electrical Resistivity Tomographies (ERT), which have already been proven to be useful and efficient enough to describe soil water changes and the structural variability in soils. Our results enhanced the relevant impact of compaction on water transfer and, therefore, on availability of water reserves for plants. Compacted zones created by Wheel Tracks and the tillage pan restricted root penetration and remained wetter than the loosen matrix. However these results depend on climatic events. As observed after rainfalls, reduced infiltration due to compaction was overcome by preferential flow pathways identified at borders of clods where roots were relatively clumped. In addition, the ploughpan was shown to be a restrictive layer for water flow. These combined effects modified in time water stocks in the rooting zone as well as the structural resilience of clods.
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Characterisation of the structural heterogeneity of the soil tilled layer by using in situ 2D and 3D electrical resistivity measurements
Soil and Tillage Research, 2009Co-Authors: Maud Seger, Isabelle Cousin, Hubert Boizard, Anthony Frison, Guy RichardAbstract:Compaction is responsible for soil physical degradation by affecting soil structure, i.e. the arrangement of soil particles in space. Under Wheel Tracks, the soil density increases and the porosity decreases, which affects soil physical properties. Conventional methods of measuring soil compaction are time consuming, destructive and give misinterpretations by using 2D informations. We then need non-destructive tools that enable the description of the soil structure in the field at a centimetric or decimetric resolution. The aim of this study is to discuss the feasibility of using a geophysical method, the electrical resistivity one, to describe the complex 3D structure of the cultivated layer in an agricultural field. The studied zone - a 2.4 m x 1.4 m field plot - consists in a compacted band, first created by a heavy tractor, then fragmented by ploughing. 3D information about the structure was given by the analysis of ten successive morphological profiles spaced 10 cm apart. They have shown that the structure was composed by dense aggregates, loose material and large voids. The studied zone was characterised by electrical prospectings thanks to both 2D investigation (Wenner arrays of 24 electrodes) and 3D investigation (square arrays of 48 electrodes), with electrodes spaced 10 cm apart. The analysis of apparent resistivity and interpreted resistivity data has shown that we can localise zones with large voids, loose material or compacted aggregates. These results have been confirmed by direct observations on soil profiles. The 3D electrical resistivity prospecting method thus enables the description of the 3D heterogeneity of the tilled layer at a decimetric resolution and constitutes then an alternative tool to the X-ray tomography for studies in the field.
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Can electrical resistivity tomography describe soil structure evolution?
2003Co-Authors: Anatja Samouëlian, Guy Richard, Isabelle Cousin, Alain Tabbagh, Ary BruandAbstract:Variations of soil structure is significant for the understanding of water and gas transfer in soil profiles. In the context of arable land, soil structure can be compacted due to either agriculture operation (Wheel Tracks), or hardsetting and crusting processes. As a consequence, soil porosity is reduced which may lead to decrease water infiltration and to anoxic conditions. Porosity can be increased by cracks formation due to swelling and shrinking phenomenon. We present here a laboratory experiment based on soil electrical characteristics. Electrical resistivity allows a non destructive three dimensional and dynamical analysis of the soil structure. Our main objective is to detect cracks in the soil. Cracks form an electrical resistant object and the contrast of resistivity between air and soil is large enough to be detected. Our sample is an undisturbed soil block 240mm*170mm*160mm with an initial structure compacted by Wheel traffic. Successive artificial cracks are generated. Electrodes built with 2 mm ceramic cups permit a good electrical contact at the soil surface whatever its water content. They are installed 15 mm apart and the electrical resistivity is monitored using a dipole-dipole and wenner multi-electrodes 2D imaging method which gives a picture of the subsurface resistivity. The interpreted resistivity sections show the major soil structure. The electrical response changes with the cracks formation. The structure information extracted from the electrical map is in good agreement with the artificially man-made cracks. These first results demonstrate the relevance of high resolution electrical imaging of the soil profile. Further experiments need to be carried out in order to monitor natural soil structure evolution during wetting-drying cycles.
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effect of compaction on the porosity of a silty soil influence on unsaturated hydraulic properties
European Journal of Soil Science, 2001Co-Authors: Guy Richard, J F Sillon, Ary Bruand, Isabelle Cousin, J GuerifAbstract:Summary Tillage and traffic modify soil porosity and pore size distribution, leading to changes in the unsaturated hydraulic properties of the tilled layer. These changes are still difficult to characterize. We have investigated the effect of compaction on the change in the soil porosity and its consequences for water retention and hydraulic conductivity. A freshly tilled layer and a soil layer compacted by Wheel Tracks were created in a silty soil to obtain contrasting bulk densities (1.17 and 1.63 g cm−3, respectively). Soil porosity was analysed by mercury porosimetry, and scanning electron microscopy was used to distinguish between the textural pore space and the structural pore space. The laboratory method of Wind (direct evaporation) was used to measure the hydraulic properties in the tensiometric range. For water potentials < −20 kPa, the compacted layer retained more water than did the uncompacted layer, but the relation between the hydraulic conductivity and the water ratio (the volume of water per unit volume of solid phase) was not affected by the change in bulk density. Compaction did not affect the textural porosity (i.e. matrix porosity), but it created relict structural pores accessible only through the micropores of the matrix. These relict structural pores could be the reason for the change in the hydraulic properties due to compaction. They can be used as an indicator of the consequences of compaction on unsaturated hydraulic properties. The modification of the pore geometry during compaction results not only from a decrease in the volume of structural pores but also from a change in the relation between the textural pores and the remaining structural pores.
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Effect of compaction on the porosity of a silty soil: influence on unsaturated hydraulic properties.
European Journal of Soil Science, 2001Co-Authors: Guy Richard, J F Sillon, Ary Bruand, Isabelle Cousin, M. GuérifAbstract:Tillage and traffic modify soil porosity and pore size distribution, leading to changes in the unsaturated hydraulic properties of the tilled layer. These changes are still difficult to characterize. We have investigated the effect of compaction on the change in the soil porosity and its consequences for water retention and hydraulic conductivity. A freshly tilled layer and a soil layer compacted by Wheel Tracks were created in a silty soil to obtain contrasting bulk densities (1.17 and 1.63 g cm-3, respectively). Soil porosity was analysed by mercury porosimetry, and scanning electron microscopy was used to distinguish between the textural pore space and the structural pore space. The laboratory method of Wind (direct evaporation) was used to measure the hydraulic properties in the tensiometric range. For water potentials
Romain Armand - One of the best experts on this subject based on the ideXlab platform.
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runoff generation related to intra field soil surface characteristics variability application to conservation tillage context
Soil & Tillage Research, 2009Co-Authors: Romain Armand, Christian Bockstaller, Anneveronique Auzet, P M Van DijkAbstract:Abstract Conservation tillage (CT) constitutes one way to limit on- and off-site impacts of soil erosion. Literature analysis suggests that CT is more effective in reducing soil erosion than surface runoff. The effect on runoff mitigation may be rather limited and in some cases, CT causes runoff to increase compared to conventional tillage systems. From the review of infiltrometry and runoff studies, we have concluded that runoff mitigation can be explained by infiltrability improvement of the soil profile and limitation of surface structural degradation. As data on soil profile infiltration are now better documented, we choose to study how the surface may limit runoff generation. To describe soil surface ability to generate runoff, soil surface characteristics (SSC) descriptors were used. This study investigates small-scale spatial variability of SSC which is usually smoothed by runoff measurements at higher scale. Two patterns of SSC were especially studied. One is the pattern created by tillage in maize field, made up of three features (seedbed, seed line and Wheel track) which was investigated through small plots SSC surveys. The other is the pattern created by the alternation of mulch and bare patches which was investigated by rainfall simulations. SSC surveys reveal that mulch and crust cover varied amongst features created by tillage. Crust extent, on the whole, is higher under conventional tillage but presents differences between tillage features. Under reduced tillage (RT), seed lines and Wheel Tracks present a lower mulch cover and a higher crust extent. No-tillage (NT) is characterized by the absence of the tillage pattern and a lower crust extent. Concerning the influence of the mulch pattern, no effect was observed on runoff amounts under simulated rainfall. Further research is required to assess pattern effects in CT context, especially measuring which features mostly contribute to runoff. There is also a clear need to adapt infiltrometry and rainfall simulation procedures to correctly take CT specificity (e.g. mulch presence) into account.
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Runoff generation related to intra-field soil surface characteristics variability application to conservation tillage context
Soil and Tillage Research, 2009Co-Authors: Romain Armand, Christian Bockstaller, Anneveronique Auzet, Paul Van DijkAbstract:Conservation tillage (CT) constitutes one way to limit on- and off-site impacts of soil erosion. Literature analysis suggests that CT is more effective in reducing soil erosion than surface runoff. The effect on runoff mitigation may be rather limited and in some cases, CT causes runoff to increase compared to conventional tillage systems. Fromthe reviewof infiltrometry and runoff studies,we have concluded that runoff mitigation can be explained by infiltrability improvement of the soil profile and limitation of surface structural degradation. As data on soil profile infiltration are nowbetter documented,we choose to study howthe surfacemay limit runoff generation. To describe soil surface ability to generate runoff, soil surface characteristics (SSC) descriptors were used. This study investigates small-scale spatial variability of SSC which is usually smoothed by runoff measurements at higher scale. Two patterns of SSC were especially studied. One is the pattern created by tillage in maize field,made up of three features (seedbed, seed line and Wheel track) which was investigated through small plots SSC surveys. The other is the pattern created by the alternation of mulch and bare patches which was investigated by rainfall simulations. SSC surveys reveal thatmulch and crust cover varied amongst features created by tillage. Crust extent, on the whole, is higher under conventional tillage but presents differences between tillage features. Under reduced tillage (RT), seed lines and Wheel Tracks present a lower mulch cover and a higher crust extent. No-tillage (NT) is characterized by the absence of the tillage pattern and a lower crust extent. Concerning the influence of the mulch pattern, no effect was observed on runoff amounts under simulated rainfall. Further research is required to assess pattern effects in CT context, especially measuring which features mostly contribute to runoff. There is also a clear need to adapt infiltrometry and rainfall simulation procedures to correctly take CT specificity (e.g. mulch presence) into account.
Ary Bruand - One of the best experts on this subject based on the ideXlab platform.
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Can electrical resistivity tomography describe soil structure evolution?
2003Co-Authors: Anatja Samouëlian, Guy Richard, Isabelle Cousin, Alain Tabbagh, Ary BruandAbstract:Variations of soil structure is significant for the understanding of water and gas transfer in soil profiles. In the context of arable land, soil structure can be compacted due to either agriculture operation (Wheel Tracks), or hardsetting and crusting processes. As a consequence, soil porosity is reduced which may lead to decrease water infiltration and to anoxic conditions. Porosity can be increased by cracks formation due to swelling and shrinking phenomenon. We present here a laboratory experiment based on soil electrical characteristics. Electrical resistivity allows a non destructive three dimensional and dynamical analysis of the soil structure. Our main objective is to detect cracks in the soil. Cracks form an electrical resistant object and the contrast of resistivity between air and soil is large enough to be detected. Our sample is an undisturbed soil block 240mm*170mm*160mm with an initial structure compacted by Wheel traffic. Successive artificial cracks are generated. Electrodes built with 2 mm ceramic cups permit a good electrical contact at the soil surface whatever its water content. They are installed 15 mm apart and the electrical resistivity is monitored using a dipole-dipole and wenner multi-electrodes 2D imaging method which gives a picture of the subsurface resistivity. The interpreted resistivity sections show the major soil structure. The electrical response changes with the cracks formation. The structure information extracted from the electrical map is in good agreement with the artificially man-made cracks. These first results demonstrate the relevance of high resolution electrical imaging of the soil profile. Further experiments need to be carried out in order to monitor natural soil structure evolution during wetting-drying cycles.
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effect of compaction on the porosity of a silty soil influence on unsaturated hydraulic properties
European Journal of Soil Science, 2001Co-Authors: Guy Richard, J F Sillon, Ary Bruand, Isabelle Cousin, J GuerifAbstract:Summary Tillage and traffic modify soil porosity and pore size distribution, leading to changes in the unsaturated hydraulic properties of the tilled layer. These changes are still difficult to characterize. We have investigated the effect of compaction on the change in the soil porosity and its consequences for water retention and hydraulic conductivity. A freshly tilled layer and a soil layer compacted by Wheel Tracks were created in a silty soil to obtain contrasting bulk densities (1.17 and 1.63 g cm−3, respectively). Soil porosity was analysed by mercury porosimetry, and scanning electron microscopy was used to distinguish between the textural pore space and the structural pore space. The laboratory method of Wind (direct evaporation) was used to measure the hydraulic properties in the tensiometric range. For water potentials < −20 kPa, the compacted layer retained more water than did the uncompacted layer, but the relation between the hydraulic conductivity and the water ratio (the volume of water per unit volume of solid phase) was not affected by the change in bulk density. Compaction did not affect the textural porosity (i.e. matrix porosity), but it created relict structural pores accessible only through the micropores of the matrix. These relict structural pores could be the reason for the change in the hydraulic properties due to compaction. They can be used as an indicator of the consequences of compaction on unsaturated hydraulic properties. The modification of the pore geometry during compaction results not only from a decrease in the volume of structural pores but also from a change in the relation between the textural pores and the remaining structural pores.
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Effect of compaction on the porosity of a silty soil: influence on unsaturated hydraulic properties.
European Journal of Soil Science, 2001Co-Authors: Guy Richard, J F Sillon, Ary Bruand, Isabelle Cousin, M. GuérifAbstract:Tillage and traffic modify soil porosity and pore size distribution, leading to changes in the unsaturated hydraulic properties of the tilled layer. These changes are still difficult to characterize. We have investigated the effect of compaction on the change in the soil porosity and its consequences for water retention and hydraulic conductivity. A freshly tilled layer and a soil layer compacted by Wheel Tracks were created in a silty soil to obtain contrasting bulk densities (1.17 and 1.63 g cm-3, respectively). Soil porosity was analysed by mercury porosimetry, and scanning electron microscopy was used to distinguish between the textural pore space and the structural pore space. The laboratory method of Wind (direct evaporation) was used to measure the hydraulic properties in the tensiometric range. For water potentials
M. Guérif - One of the best experts on this subject based on the ideXlab platform.
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Effect of compaction on the porosity of a silty soil: influence on unsaturated hydraulic properties.
European Journal of Soil Science, 2001Co-Authors: Guy Richard, J F Sillon, Ary Bruand, Isabelle Cousin, M. GuérifAbstract:Tillage and traffic modify soil porosity and pore size distribution, leading to changes in the unsaturated hydraulic properties of the tilled layer. These changes are still difficult to characterize. We have investigated the effect of compaction on the change in the soil porosity and its consequences for water retention and hydraulic conductivity. A freshly tilled layer and a soil layer compacted by Wheel Tracks were created in a silty soil to obtain contrasting bulk densities (1.17 and 1.63 g cm-3, respectively). Soil porosity was analysed by mercury porosimetry, and scanning electron microscopy was used to distinguish between the textural pore space and the structural pore space. The laboratory method of Wind (direct evaporation) was used to measure the hydraulic properties in the tensiometric range. For water potentials
