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Viliam Novák - One of the best experts on this subject based on the ideXlab platform.
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Estimation of macropore flow characteristics in Stony Soils of a small mountain catchment
Journal of Hydrology, 2019Co-Authors: Hana Hlaváčiková, Ladislav Holko, Michal Danko, Viliam NovákAbstract:Abstract The rapid movement of water in a complex system of preferential pathways in Soils is a common natural phenomenon. However, quantification of the properties of this phenomenon is not easy and such results are not often found in the literature. The paper presents results of quantification of the number of macropores, their relative volume and the ratio of water infiltrating through the macropores for five study sites with Stony Soils located in a mountain catchment of northern Slovakia. These characteristics were calculated from the saturated and unsaturated soil hydraulic conductivities under the assumptions of the Poiseuille’s law. Saturated hydraulic conductivities were estimated by single ring infiltrometer measurements in the field and by falling head method in the laboratory. Unsaturated hydraulic conductivities were estimated by tension infiltration measurements in the field (using a minidisc infiltrometer, Decagon Devices). The largest amount of macropores (defined as the pores with radius larger than 1.5 mm) in the entire soil profile (7–5276 per 1 m2) was found at forest sites overgrown by spruce with high to extremely high stoniness. The number of macropores decreased with depth of the soil profile at all study sites. The contribution of macropore flow to water infiltration varied from approximately 63% to almost 100%. Although macropores can conduct a large proportion of water, their relative volume is small (0.001–0.9%). The relative volume of all macropores (active and non-active) estimated from the soil porosity and the water retention function was in the range 2–23%.
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the effects of rock fragment shapes and positions on modeled hydraulic conductivities of Stony Soils
Geoderma, 2016Co-Authors: Hana Hlaváčiková, Viliam Novák, Jirka SimůnekAbstract:Abstract Mountainous Soils usually contain a large number of rock fragments, particles with a diameter larger than 2 mm, which can influence soil hydraulic properties that are required to quantitatively describe soil water movement in Stony Soils. The objective of this study was to numerically estimate both the saturated hydraulic conductivity of a Stony soil and its dependence on a relative content of rock fragments (stoniness), and the shape, position and distribution of rock fragments in a soil matrix. The assessment method was based on a numerical version of Darcy's classic experiment that involved steady-state flow through a porous material under a unit hydraulic gradient. Our experiments, involving hypothetical Stony Soils in this particular case, were simulated using mainly the two-dimensional (2D) numerical model, HYDRUS-2D. A limited number of simulations were carried out using a three-dimensional HYDRUS model. Three different shapes of hypothetical rock fragments were used in the study: a sphere, an ellipsoid with two different positions, and a pyramid, all represented by their 2D cross-sections (i.e., a circle, an ellipse, and a triangle, respectively). The mean relative effective saturated hydraulic conductivity ( K rs ) for the same stoniness was almost the same for all simulated scenarios and fine soil textures. A stoniness between 0.07 and 0.5 cm 3 cm − 3 can cause a decrease of K rs in the range of 0.17–0.70. Numerical experiments were divided into 3 scenarios. The largest and the smallest values of K rs were different for different shapes of RFs (scenario A), different orientations of the slab-sided elliptical RFs (scenario B), and regular or irregular distributions of spherical RFs (scenario C). The largest difference between K rs values (0.26) was found in scenario B when the slab-sided elliptical RFs were oriented either horizontally or vertically for stoniness of 0.24 or 0.31 cm 3 cm − 3 . Simulated K rs values were underestimated in all scenarios as compared to the Ravina and Magier (1984) function. The smallest differences (− 1.1%–2.5%) between numerically simulated and calculated (the Corring and Churchill (1961) method for a cylindrical shape of RFs) K rs values were found for scenario A with its 2D representation of spherical rock fragments. Calculated (the Corring and Churchill (1961) method for a spherical shape of RFs) K rs values corresponded well with those simulated using a 3D representation of spherical rock fragments. Numerical models provide a unique opportunity to evaluate the effects of different factors on the saturated hydraulic conductivity of Stony Soils that may be nearly impossible to measure in practice.
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on the role of rock fragments and initial soil water content in the potential subsurface runoff formation
Journal of Hydrology and Hydromechanics, 2015Co-Authors: Hana Hlaváčiková, Viliam Novák, Ladislav HolkoAbstract:Stony Soils are composed of fractions (rock fragments and fine soil) with different hydrophysical characteristics. Although they are abundant in many catchments, their properties are still not well understood. This article presents basic characteristics (texture, stoniness, saturated hydraulic conductivity, and soil water retention) of Stony Soils from a mountain catchment located in the highest part of the Carpathian Mountains and summarizes results of water flow modeling through a hypothetical Stony soil profile. Numerical simulations indicate the highest vertical outflow from the bottom of the profile in Soils without rock fragments under ponding infiltration condition. Simulation of a more realistic case in a mountain catchment, i.e. infiltration of intensive rainfall, shows that when rainfall intensity is lower than the saturated hydraulic conductivity of the Stony soil, the highest outflow is predicted in a soil with the highest stoniness and high initial water content of soil matrix. Relatively low available retention capacity in a Stony soil profile and consequently higher unsaturated hydraulic conductivity leads to faster movement of the infiltration front during rainfall.
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a relatively simple scaling method for describing the unsaturated hydraulic functions of Stony Soils
Journal of Plant Nutrition and Soil Science, 2014Co-Authors: Hana Hlaváčiková, Viliam NovákAbstract:Few if any methods exist to estimate the effects of stone content (stoniness) on the unsaturated soil hydraulic properties. A relatively simple scaling method is presented to estimate the hydraulic conductivity of unsaturated Stony Soils having different stone contents. A key assumption of the method is that van Genuchten's water retention parameters α and n of the fine soil fraction are the same as those of the Stony soil. The method further assumes a linearly decreasing relationship between the saturated hydraulic conductivity and the stone content, based on previous numerical simulations. Using the proposed method, it is possible to calculate the hydraulic conductivity of unsaturated Stony Soils, knowing the saturated hydraulic conductivity of the fine soil fraction, the retention curve of the fine soil fraction, and the particular stoniness of the soil.
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the influence of stoniness and canopy properties on soil water content distribution simulation of water movement in forest Stony soil
European Journal of Forest Research, 2012Co-Authors: Viliam Novák, Karol KňavaAbstract:Mountainous forest Soils usually contain a large number of rock fragments (particle diameter >2 mm), which influence soil properties. Data characterizing hydraulic properties of these Soils usually describe only the fine soil fraction (particle diameter <2 mm) properties. To quantitatively describe soil water movement in Stony Soils, it is necessary to evaluate effective hydrophysical characteristics, involving the influence of stones, that is, the effective hydraulic conductivity and retention capacity should be known. Properties of evaporating surface (plant canopy) also play important role in formation of soil water movement and retention. This work presents results of the study of rock fragments (stoniness) effect on soil water content profiles and soil water dynamics during the season. Stony and homogeneous soil behavior is compared. The effect of different canopies (spruce forest, low vegetation) and bare soil in both types of Soils on soil water dynamics is also studied. Stones as a part of soil are decreasing its water capacity and hydraulic conductivity as well. This is expressing in the decrease of Stony soil water content retention capacity. High interception capacity of trees, followed by the low undercanopy precipitation, leads to the decreased soil water content of the upper soil layer. Combination of Stony soil and dense forest canopy led to the low undercanopy precipitation, to relatively low infiltration totals into soil, and to decreased outflow.
Isabelle Cousin - One of the best experts on this subject based on the ideXlab platform.
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field scale estimation of the volume percentage of rock fragments in Stony Soils by electrical resistivity
Catena, 2012Co-Authors: Marion Tetegan, Bernard Nicoullaud, Catherine Pasquier, A Besson, Alain Bouthier, Hocine Bourennane, C Desbourdes, D King, Isabelle CousinAbstract:Abstract Analysing the properties and functional characteristics of heterogeneous Soils containing several phases requires a correct estimation of the volume proportion of each phase. In the case of Stony Soils, the volume percentage of the content of rock fragments remains difficult to estimate in situ. This paper presents a method that uses field spatial electrical resistivity measurements to determine the volume proportion of rock fragments. Based on the hypothesis that the electrical resistivity signal noise increases as the proportion of rock fragments increases, a model was developed that uses the standard deviation of the apparent electrical resistivity measurements over a small area as an indicator of rock fragment contents. The model was tested on three study areas of several hectares containing soil units with varying quantities of rock fragments. The estimation of the rock fragment content was accurate, and the error estimation of about 6% was the same order of magnitude as the Bussian model (1983). The developed model strongly depends on the water content in the soil and the rock type and must be calibrated in each context. Nevertheless, estimations of the rock fragment content in Stony Soils can be performed efficiently in the surface horizon as well as all along the soil profile.
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the contribution of rock fragments to the available water content of Stony Soils proposition of new pedotransfer functions
Geoderma, 2011Co-Authors: Marion Tetegan, Bernard Nicoullaud, Alain Bouthier, Denis Baize, Isabelle CousinAbstract:Abstract The contribution of rock fragments to the soil available water content (SAWC) of Stony soil has been quantified by measurements of bulk density and gravimetric water content at different water potentials on rock fragments of different lithologies: flints, cherts, chalks, gaizes and limestones. More than 1000 pebbles (2 cm
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contribution of Stony phase in hydric properties of Soils
Proceedings of the 19th World Congress of Soil Science: Soil solutions for a changing world Brisbane Australia 1-6 August 2010. Symposium 2.1.1 optimi, 2010Co-Authors: Marion Tetegan, Isabelle Cousin, Alain Bouthier, B Nicoullaud, R J Gilkes, N PrakongkepAbstract:Stony Soils cover about 30% of the surface Soils of Western Europe, and 60% in Mediterranean areas. They consist of rock fragments whose diameters are larger than 2 mm (the rock fragment). These fragments may alter the physical, chemical and agricultural properties of Soils. To better understand the role of stones in the water supply of crops, structure and hydric properties of coarse elements of Stony Soils were studied. Monitoring the moisture was done on coarse fragments from sedimentary rocks, and revealed that rock fragments can store as much water as the fine earth. Applying the concept of field capacity and wilting point to coarse fragments, a simple pedotransfer function was defined to estimate the contribution of the pebbles to the Available Water Content of a Stony soil.
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influence of rock fragments on the water retention and water percolation in a calcareous soil
Catena, 2003Co-Authors: Isabelle Cousin, Bernard Nicoullaud, Caroline CoutadeurAbstract:Abstract The water retention properties of a calcareous soil containing rock fragments have been determined in the laboratory thanks to pressure plate measurements done on both the fine earth and the rock fragments from the soil. The available water content (AWC) has been calculated from these data. We have shown that when the rock fragments are neglected, the AWC can be overestimated by 39%. When we do not neglect their volume but when their hydraulic properties are not considered, the AWC can be underestimated by 34%. By using a reservoir model, we have also calculated the effect of rock fragments on water percolation to groundwater. Depending of the climatic characteristics of the year, the underestimation of percolation when we neglect the rock fragments can reach up to 14.9% and the overestimation when we neglect their hydraulic properties can be equal to 15.8%. These findings emphasise the role of the rock fragments on the water supply in Stony Soils.
Hana Hlaváčiková - One of the best experts on this subject based on the ideXlab platform.
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the role of Stony Soils in hillslope and catchment runoff formation
Journal of Hydrology and Hydromechanics, 2020Co-Authors: Babar Mujtaba, Hana Hlaváčiková, Michal Danko, Joao L M P De Lima, Ladislav HolkoAbstract:The role of Stony Soils in runoff response of mountain catchments is rarely studied. We have compared simulated response of Stony Soils with measured catchment runoff for events caused by rains of small and high intensities in the mountain catchment of the Jalovecký Creek, Slovakia. The soil water response was simulated for three sites with stoniness 10–65% using the Hydrus-2D single porosity model. Soil hydraulic parameters employed in the modelling, i. e. the saturated hydraulic conductivity and parameters of the soil water retention curves, were obtained by two approaches, namely by the Representative Elementary Volume approach (REVa) and by the inverse modelling with Hydrus-1D model (IMa). The soil water outflow hydrographs simulated by Hydrus-2D were compared to catchment runoff hydrographs by analysing their skewness and peak times. Measured catchment runoff hydrographs were similar to simulated soil water outflow hydrographs for about a half of rainfall events. Interestingly, most of them were caused by rainfalls with small intensity (below 2.5 mm/10 min). The REV approach to derive soil hydraulic parameters for soil water outflow modelling provided more realistic shapes of soil water outflow hydrographs and peak times than the IMa approach.
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Estimation of macropore flow characteristics in Stony Soils of a small mountain catchment
Journal of Hydrology, 2019Co-Authors: Hana Hlaváčiková, Ladislav Holko, Michal Danko, Viliam NovákAbstract:Abstract The rapid movement of water in a complex system of preferential pathways in Soils is a common natural phenomenon. However, quantification of the properties of this phenomenon is not easy and such results are not often found in the literature. The paper presents results of quantification of the number of macropores, their relative volume and the ratio of water infiltrating through the macropores for five study sites with Stony Soils located in a mountain catchment of northern Slovakia. These characteristics were calculated from the saturated and unsaturated soil hydraulic conductivities under the assumptions of the Poiseuille’s law. Saturated hydraulic conductivities were estimated by single ring infiltrometer measurements in the field and by falling head method in the laboratory. Unsaturated hydraulic conductivities were estimated by tension infiltration measurements in the field (using a minidisc infiltrometer, Decagon Devices). The largest amount of macropores (defined as the pores with radius larger than 1.5 mm) in the entire soil profile (7–5276 per 1 m2) was found at forest sites overgrown by spruce with high to extremely high stoniness. The number of macropores decreased with depth of the soil profile at all study sites. The contribution of macropore flow to water infiltration varied from approximately 63% to almost 100%. Although macropores can conduct a large proportion of water, their relative volume is small (0.001–0.9%). The relative volume of all macropores (active and non-active) estimated from the soil porosity and the water retention function was in the range 2–23%.
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the effects of rock fragment shapes and positions on modeled hydraulic conductivities of Stony Soils
Geoderma, 2016Co-Authors: Hana Hlaváčiková, Viliam Novák, Jirka SimůnekAbstract:Abstract Mountainous Soils usually contain a large number of rock fragments, particles with a diameter larger than 2 mm, which can influence soil hydraulic properties that are required to quantitatively describe soil water movement in Stony Soils. The objective of this study was to numerically estimate both the saturated hydraulic conductivity of a Stony soil and its dependence on a relative content of rock fragments (stoniness), and the shape, position and distribution of rock fragments in a soil matrix. The assessment method was based on a numerical version of Darcy's classic experiment that involved steady-state flow through a porous material under a unit hydraulic gradient. Our experiments, involving hypothetical Stony Soils in this particular case, were simulated using mainly the two-dimensional (2D) numerical model, HYDRUS-2D. A limited number of simulations were carried out using a three-dimensional HYDRUS model. Three different shapes of hypothetical rock fragments were used in the study: a sphere, an ellipsoid with two different positions, and a pyramid, all represented by their 2D cross-sections (i.e., a circle, an ellipse, and a triangle, respectively). The mean relative effective saturated hydraulic conductivity ( K rs ) for the same stoniness was almost the same for all simulated scenarios and fine soil textures. A stoniness between 0.07 and 0.5 cm 3 cm − 3 can cause a decrease of K rs in the range of 0.17–0.70. Numerical experiments were divided into 3 scenarios. The largest and the smallest values of K rs were different for different shapes of RFs (scenario A), different orientations of the slab-sided elliptical RFs (scenario B), and regular or irregular distributions of spherical RFs (scenario C). The largest difference between K rs values (0.26) was found in scenario B when the slab-sided elliptical RFs were oriented either horizontally or vertically for stoniness of 0.24 or 0.31 cm 3 cm − 3 . Simulated K rs values were underestimated in all scenarios as compared to the Ravina and Magier (1984) function. The smallest differences (− 1.1%–2.5%) between numerically simulated and calculated (the Corring and Churchill (1961) method for a cylindrical shape of RFs) K rs values were found for scenario A with its 2D representation of spherical rock fragments. Calculated (the Corring and Churchill (1961) method for a spherical shape of RFs) K rs values corresponded well with those simulated using a 3D representation of spherical rock fragments. Numerical models provide a unique opportunity to evaluate the effects of different factors on the saturated hydraulic conductivity of Stony Soils that may be nearly impossible to measure in practice.
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on the role of rock fragments and initial soil water content in the potential subsurface runoff formation
Journal of Hydrology and Hydromechanics, 2015Co-Authors: Hana Hlaváčiková, Viliam Novák, Ladislav HolkoAbstract:Stony Soils are composed of fractions (rock fragments and fine soil) with different hydrophysical characteristics. Although they are abundant in many catchments, their properties are still not well understood. This article presents basic characteristics (texture, stoniness, saturated hydraulic conductivity, and soil water retention) of Stony Soils from a mountain catchment located in the highest part of the Carpathian Mountains and summarizes results of water flow modeling through a hypothetical Stony soil profile. Numerical simulations indicate the highest vertical outflow from the bottom of the profile in Soils without rock fragments under ponding infiltration condition. Simulation of a more realistic case in a mountain catchment, i.e. infiltration of intensive rainfall, shows that when rainfall intensity is lower than the saturated hydraulic conductivity of the Stony soil, the highest outflow is predicted in a soil with the highest stoniness and high initial water content of soil matrix. Relatively low available retention capacity in a Stony soil profile and consequently higher unsaturated hydraulic conductivity leads to faster movement of the infiltration front during rainfall.
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a relatively simple scaling method for describing the unsaturated hydraulic functions of Stony Soils
Journal of Plant Nutrition and Soil Science, 2014Co-Authors: Hana Hlaváčiková, Viliam NovákAbstract:Few if any methods exist to estimate the effects of stone content (stoniness) on the unsaturated soil hydraulic properties. A relatively simple scaling method is presented to estimate the hydraulic conductivity of unsaturated Stony Soils having different stone contents. A key assumption of the method is that van Genuchten's water retention parameters α and n of the fine soil fraction are the same as those of the Stony soil. The method further assumes a linearly decreasing relationship between the saturated hydraulic conductivity and the stone content, based on previous numerical simulations. Using the proposed method, it is possible to calculate the hydraulic conductivity of unsaturated Stony Soils, knowing the saturated hydraulic conductivity of the fine soil fraction, the retention curve of the fine soil fraction, and the particular stoniness of the soil.
Marion Tetegan - One of the best experts on this subject based on the ideXlab platform.
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field scale estimation of the volume percentage of rock fragments in Stony Soils by electrical resistivity
Catena, 2012Co-Authors: Marion Tetegan, Bernard Nicoullaud, Catherine Pasquier, A Besson, Alain Bouthier, Hocine Bourennane, C Desbourdes, D King, Isabelle CousinAbstract:Abstract Analysing the properties and functional characteristics of heterogeneous Soils containing several phases requires a correct estimation of the volume proportion of each phase. In the case of Stony Soils, the volume percentage of the content of rock fragments remains difficult to estimate in situ. This paper presents a method that uses field spatial electrical resistivity measurements to determine the volume proportion of rock fragments. Based on the hypothesis that the electrical resistivity signal noise increases as the proportion of rock fragments increases, a model was developed that uses the standard deviation of the apparent electrical resistivity measurements over a small area as an indicator of rock fragment contents. The model was tested on three study areas of several hectares containing soil units with varying quantities of rock fragments. The estimation of the rock fragment content was accurate, and the error estimation of about 6% was the same order of magnitude as the Bussian model (1983). The developed model strongly depends on the water content in the soil and the rock type and must be calibrated in each context. Nevertheless, estimations of the rock fragment content in Stony Soils can be performed efficiently in the surface horizon as well as all along the soil profile.
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the contribution of rock fragments to the available water content of Stony Soils proposition of new pedotransfer functions
Geoderma, 2011Co-Authors: Marion Tetegan, Bernard Nicoullaud, Alain Bouthier, Denis Baize, Isabelle CousinAbstract:Abstract The contribution of rock fragments to the soil available water content (SAWC) of Stony soil has been quantified by measurements of bulk density and gravimetric water content at different water potentials on rock fragments of different lithologies: flints, cherts, chalks, gaizes and limestones. More than 1000 pebbles (2 cm
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contribution of Stony phase in hydric properties of Soils
Proceedings of the 19th World Congress of Soil Science: Soil solutions for a changing world Brisbane Australia 1-6 August 2010. Symposium 2.1.1 optimi, 2010Co-Authors: Marion Tetegan, Isabelle Cousin, Alain Bouthier, B Nicoullaud, R J Gilkes, N PrakongkepAbstract:Stony Soils cover about 30% of the surface Soils of Western Europe, and 60% in Mediterranean areas. They consist of rock fragments whose diameters are larger than 2 mm (the rock fragment). These fragments may alter the physical, chemical and agricultural properties of Soils. To better understand the role of stones in the water supply of crops, structure and hydric properties of coarse elements of Stony Soils were studied. Monitoring the moisture was done on coarse fragments from sedimentary rocks, and revealed that rock fragments can store as much water as the fine earth. Applying the concept of field capacity and wilting point to coarse fragments, a simple pedotransfer function was defined to estimate the contribution of the pebbles to the Available Water Content of a Stony soil.
Jean Poesen - One of the best experts on this subject based on the ideXlab platform.
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climate effects on soil erodibility
Earth Surface Processes and Landforms, 2008Co-Authors: M Salvador P Sanchis, L Borselli, Dino Torri, Jean PoesenAbstract:Soil erodibility data, calculated using measured soil loss from standard runoff plots, collected over at least one year and applying the standard requirements for calculating the soil erodibility factor (K) of the Universal Soil Loss Equation (USLE), have been analysed to investigate whether climate affects the susceptibility of Soils to water erosion. In total, more than 300 K-values extracted from the literature have been analysed. Due to the limited availability of data related to the characteristics of the soil and the location of the measuring sites, all the analysis has been carried out using only soil textural characteristics, organic matter content, rock fragment content and the some general characteristics of the climatic zone where the plots were located. The first evidence of a strong climate effect on soil erodibility is shown by the seasonal variation of mean monthly soil erodibility (Km). Using data collected in the USA and Italy an effect of mean monthly air temperature on Km could be identified. Data collected in Indonesia (where mean monthly air temperature remains fairly constant throughout the year) showed comparable variations of monthly soil erodibility. However, it was impossible to explain these variations in Km as no other data than mean monthly air temperature were available. Mean annual soil erodibility shows a clear climate effect. Soil erodibilities can be subdivided into two large groups, one corresponding to Soils in cool climates (Df and Cf climate according to the Koppen–Geiger climate classification) and another to Soils located in warm climates (tropical Af and Aw climates). Erodibilities of Mediterranean Soils (found under Cs climate) plot among the Soils found in Af and Aw climates. These subdivisions can be made for both Stony and non-Stony Soils. Limited data suggest that soil aggregate stability is a good predictor for explaining soil erodibility variations between different climate zones. Copyright © 2007 John Wiley & Sons, Ltd.
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evaporation losses from bare Soils as influenced by cultivation techniques in semi arid regions
Agricultural Water Management, 2000Co-Authors: Hj Mellouli, Jean Poesen, B Van Wesemael, R HartmannAbstract:The impact of cultivation techniques on the evaporation from bare Soils was investigated in the laboratory. Two soil-types, which are important resources for rainfed cultivation of olives and almonds in semi-arid regions, were selected: a loamy sand soil and a Stony (loam) soil. Evaporation from the soil surface is an important loss of soil moisture in these farming systems since a large percentage of the soil is kept bare in order to maximise the water availability for the tree crop. For the loamy sand soil the impacts of a straw mulch and treatment of the topsoil with olive mill effluent (OME) were tested. For the Stony soil the effects of different rock fragment contents and distribution within the soil profile were tested. After thoroughly wetting with simulated rainfall and allowing the soil moisture to redistribute, the columns were subjected to evaporation for 46 days. Cumulative evaporation depth of Soils treated with OME was 28% lower than that of the control soil. A similar reduction, be it lower (16%) was observed for the soil with a high rock fragment content by volume (Rva 0.35 m 3 m ˇ3 ). The straw mulch and rock fragment mulch did not have an impact on the cumulative evaporation depth after 46 days. Furthermore, the time required to reach half of the total evaporation losses (d0.5) increased from 9 days for the control soil (loamy sand) to 24 days for the soil impregnated with OME and to 15 days for the straw mulch treatment. The same trend was observed for the Stony Soils: an increase in d0.5 from 4 days for the control soil (Rva 0.19 m 3 m ˇ3 ) to 7 days for the soil with Rva 0.35 m 3 m ˇ3 and to 8 days for the rock fragment mulch. These experiments show that the changes in water retention capacity of the topsoil by treatment with a hydrophobic substance (OME) or an increase in rock fragment content have a
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fine earth translocation by tillage in Stony Soils in the guadalentin south east spain an investigation using caesium 134
Soil & Tillage Research, 1999Co-Authors: T A Quine, Jean Poesen, Gerard Govers, Des E Walling, Bas Van Wesemael, J MartinezfernandezAbstract:Tillage erosion is increasingly recognised as an important soil erosion process on agricultural land. In view of its potential significance, there is a clear need to broaden the experimental database for the magnitude of tillage erosion to include a range of tillage implements and agricultural environments. The study discussed in this paper sought to address the need for such data by examining tillage erosion by a duckfoot chisel plough in Stony Soils on steep slopes in a semi-arid environment. Results of the investigation of coarse fraction (rock fragment) translocation by tillage in this environment have been presented elsewhere and the paper focuses on tillage translocation and erosion of the fine earth. Tillage translocation was measured at 10 sites, representing both upslope and downslope tillage by a duckfoot chisel plough on five different slopes, with tangents ranging from 0.02 to 0.41. A fine-earth tracer, comprising fine earth labelled with 134 Cs, was introduced into the plough layer before tillage. After a single pass of the plough, incremental samples of plough soil were excavated and sieved to separate the fine earth from the rock fragments. Translocation of the fine-earth tracer was established by analysing the 134 Cs content of the samples of fine earth. These data were used to establish translocation distances for each combination of slope and tillage direction. Translocation distances of the fine earth were not significantly different from translocation distances of the coarse fraction. For all sites, except uphill on the 0.41 slope, translocation distances were found to be linearly related to slope tangent. The soil flux due to tillage for each site was calculated using the translocation distance and the mass per unit area of the plough layer. For slopes with tangents <0.25, the relationship between soil flux and tangent was linear and the soil flux coefficient derived was 520-660 kg m -1 per pass. This is much larger than the coefficients found in other studies and this high magnitude is attributed to the non-cohesive nature and high rock fragment content of the soil in this investigation. A second contrast with previous studies was found in non-linearity in the relationship between soil flux and tangent when steeper slopes were included. This was a product of variation in plough depth between the steepest slopes and the remainder of the study area. On the basis of the study it is suggested that an improved understanding of tillage erosion may be obtained by considering the dual processes of tillage detachment (mass per unit area of soil subject to tillage) and tillage displacement (equivalent to translocation distance per pass) in assessing, comparing and modelling tillage translocation. An improved model is proposed that recognises the complexity of soil redistribution by tillage, provides a framework for process-based investigation of the controls on tillage fluxes, and allows identification of potential self-limiting conditions for tillage erosion.
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contribution of gully erosion to sediment production in cultivated lands and rangelands
IAHS Publ., 1996Co-Authors: Jean Poesen, Karel Vandaele, Bas Van WesemaelAbstract:Sediment production by gully erosion and by interrill and rill erosion in three study areas, representing contrasting agricultural environ ments (i.e. central Belgium, southeast Portugal and southeast Spain), is assessed through soil erosion mapping and analysis of aerial photos. The data indicate that mean annual soil losses due to ephemeral gullying are far from negligible in the studied environments: i.e. 3.6 m3 ha4 year1 in central Belgium, 3.2 m3 ha"1 year"1 in southeast Portugal and 9.7 m3 ha"1 year"1 in southeast Spain. Mean sediment production by ephemeral gully erosion represents 44% of total sediment produced in intensively cultivated small catchments with loess-derived Soils, but 80% or more in Mediterranean areas with Stony Soils. These figures are not constant for the studied environments but vary over time with rainfall intensity and land-use. The limited data available indicate that sediment production due to bank gully erosion is about one order of magnitude smaller than sediment produced by ephemeral gully erosion in central Belgium. The results obtained indicate that more attention should be given to the rate of ephemeral gully erosion when assessing and modelling the impact of environmental change on sediment production.