Papers by Abdallah Alaoui
Land
Soil compaction (SC) is a major threat for agriculture in Europe that affects many ecosystem func... more Soil compaction (SC) is a major threat for agriculture in Europe that affects many ecosystem functions, such as water and air circulation in soils, root growth, and crop production. Our objective was to present the results from five short-term (<5 years) case studies located along the north–south and east–west gradients and conducted within the SoilCare project using soil-improving cropping systems (SICSs) for mitigating topsoil and subsoil SC. Two study sites (SSs) focused on natural subsoil (˃25 cm) compaction using subsoiling tillage treatments to depths of 35 cm (Sweden) and 60 cm (Romania). The other SSs addressed both topsoil and subsoil SC (˃25 cm, Norway and United Kingdom;˃30 cm, Italy) using deep-rooted bio-drilling crops and different tillage types or a combination of both. Each SS evaluated the effectiveness of the SICSs by measuring the soil physical properties, and we calculated SC indices. The SICSs showed promising results—for example, alfalfa in Norway showed goo...
Mapping soil compaction – A review
Current Opinion in Environmental Science & Health
Abstract Land degradation due to soil compaction is a widespread phenomenon. Delineating maps of ... more Abstract Land degradation due to soil compaction is a widespread phenomenon. Delineating maps of topsoil compaction is a challenging task due to its dynamic nature, which is highly variable in time and space. This review paper sheds light on existing approaches and methods of mapping soil compaction. At the plot scale, there are three ways of doing so: (1) Direct measurement of penetration resistance (PR) and electrical conductivity, which can be scaled up using geostatistical approaches or georeferenced data; (2) calculation of vertical stress, taking into account the total load and contact area, soil characteristics, and machine load; and (3) computation of the pre-consolidation stress from pedo-transfer functions based on key soil properties obtained from available databases. At larger scales, indirect relationships are used to predict risk of compaction based on measured values, such as PR values, soil moisture, or organic matter, combined with a cartographic depth-to-water index derived from a light detection and ranging technique or other digital elevation model approaches. Among the examples we provide a 3D mapping based on the TASC (Tyres/Tracks And Soil Compaction) model, which opens new avenues in mapping methodology for helping practitioners, advisers, and policymakers to mitigate soil compaction. Since subsoil compaction can persist over decades, indicating a long memory effect (especially in the case of afforestation), knowledge of previous land uses must be taken into account for mapping areas subject to soil damage. Multi-stakeholder engagement can help to compile this information.
Infiltration Experiments and a Digital Elevation Model to Upscale Soil Hydrological Processes
Egu General Assembly Conference Abstracts, May 1, 2010
... Authors: Alaoui, Abdallah; Spiess, Pascal; Beyeler, Marcel; Weingartner, Rolf. ... dominant r... more ... Authors: Alaoui, Abdallah; Spiess, Pascal; Beyeler, Marcel; Weingartner, Rolf. ... dominant runoff show the potential of each area to contribute to runoff, they i) do not take into account the change in the process on temporal and spatial scales and ii) do not address the hydrological ...
Accepted management practices influence the distribution of surface-vented macropores and thus th... more Accepted management practices influence the distribution of surface-vented macropores and thus the nutrient fluxes in soil. Two ways to assess the impact of land-use change on nutrient fluxes in soils are presented: (a) estimating the bypassing ratio at the interface between the root zone and subsoil, and (b) monitoring the non-reactive tracer relative concentration vs depth distributions in the course of infiltration experiment. The 1993-1996 small-scale field experiments have shown that the bypassing ratio varied from 19 to 55% in a structured clay-loam soil. Impact of land use on the tracer relative concentration vs depth distributions was significant for small and medium cumulative infiltration (/ = 40-54 mm) but not so significant for the bigger cumulative infiltration (1= 100-108 mm).
Field measurements of water and solute transport in structured soil using TDR and radioactive tracer technique
ABSTRACT
Kinematic approach to the transport of iodide in a heavy clay soil in situ
Accepted management practices influence the distribution of surface-vented macropores and thus th... more Accepted management practices influence the distribution of surface-vented macropores and thus the nutrient fluxes in soil. Two ways to assess the impact of land-use change on nutrient fluxes in soils are presented: (a) estimating the bypassing ratio at the interface between the root zone and subsoil, and (b) monitoring the non-reactive tracer relative concentration vs depth distributions in the course of infiltration experiment. The 1993–1996 small-scale field experiments have shown that the bypassing ratio varied from 19 to 55% in a structured clay-loam soil. Impact of land use on the tracer relative concentration vs depth distributions was significant for small and medium cumulative infiltration (I = 40–54 mm) but not so significant for the bigger cumulative infiltration (I = 100–108 mm).
In a very remote tropical montane rain forest in the Ecuadorian Andes on the rim of the Amazon ba... more In a very remote tropical montane rain forest in the Ecuadorian Andes on the rim of the Amazon basin, increasing temperatures, longer dry spells, and an associated reduction in soil moisture were observed in the past 15 years. In the study ecosystem, element exports from a 9-ha large catchment with stream water are linked to the depth of water flow through soil because of vertical variations in soil chemical properties. The further increase in temperature and precipitation, as predicted by climate models, will have an impact on the water flow paths in soil and therefore alter element exports. Hence, we investigated how future element exports from this catchment in Ecuador will develop under the emission scenarios A1B and B1 for the decades 2050-2059 and 2090-2099 compared to current element exports. Discharge from the study catchment was measured in 1998-2013, partly in high resolution. Element concentrations in stream water (total organic carbon, NO 3 -N, NH 4 -N, dissolved organic nitrogen, PO 4 -P, total dissolved phosphorus, S, Cl, K, Ca, Mg, Na, Zn, Al, Mn) were measured in 1998-2012 in weekly resolution. Based on catchment properties, measured climate, and water flow data, discharge in 1998-2013 was simulated in daily resolution with the hydrological model WaSiM. From the hydrograph of surface flow, three flow classes (baseflow, intermediate, storm) were separated and linked with stream chemical properties. Element concentrations in stream water were grouped according to the flow classes and mean concentrations per flow class were calculated. Subsequently, the mean element concentration was multiplied with the mean of the annual discharge sums per flow class resulting in current element exports. For estimations of future element exports with stream water, discharge was simulated under the emission scenarios A1B and B1 for the decades 2050-2059 and 2090-2099 and separated into the three flow classes. Future element exports per scenario were calculated according to the current element exports. In both climate scenarios and decades, the number of days with high discharge rates (storm) increased and with low discharge rates (baseflow) decreased. Mean discharge rates increased by 7.5-21 % until the end of the 21st century. Annual exports of most elements were predicted to increase, particularly exports of the metals Al, Zn, and Mn (up to + 53% by the end of the 21st century) but also of NO 3 -N (+ 27%) while P exports remain unchanged. Our results demonstrate that climate change might considerably affect future element exports from this tropical montane catchment because of changing water flow paths through soil.
Modellierung der Auswirkungen der Landnutzungs- und Klimaänderungen auf die Hydrologie des Urserntals (Schweiz)
Journal of Agricultural Science, 2015
The main purpose of this study was to evaluate the effect that mechanical stresses acting under t... more The main purpose of this study was to evaluate the effect that mechanical stresses acting under the slipping driving wheels of agricultural equipment have on the soil's pore system and water flow process (surface runoff generation during extreme event). The field experiment simulated low slip (1%) and high slip (27%) on a clay loam. The stress on the soil surface and changes in the amounts of water flowing from macropores were simulated using the Tires/tracks And Soil Compaction (TASC) tool and the MACRO model, respectively. Taking a 65 kW tractor on a clay loam as a reference, results showed that an increase in slip of the rear wheels from 1% to 27% caused normal stress to increase from 90.6 kPa to 104.4 kPa at the topsoil level, and the maximum shear contact stress to rise drastically from 6.0 kPa to 61.6 kPa. At 27% slip, topsoil was sheared and displaced over a distance of 0.35 m. Excessive normal and shear stress values with high slip caused severe reductions of the soil's macroporosity, saturated hydraulic conductivity, and water quantities flowing from topsoil macropores. Assuming that, under conditions of intense rainfall on sloping land, a loss in vertical water flow would mean an increase in surface runoff, we calculated that a rainfall intensity of 100 mm h -1 and a rainfall duration of 1 h would increase the runoff coefficient to 0.79 at low slip and to 1.00 at high slip, indicating that 100% of rainwater would be transformed into surface runoff at high slip. We expect that these effects have a significant impact on soil erosion and floods in steeper terrain (slope > 15°) and across larger surface areas (> 16 m 2 ) than those included in our study.
Transport of iodide in structured clay-loam soil under maize during irrigation experiments analyzed using HYDRUS model
Biologia, 2014
ABSTRACT Transport of radioactive iodide 131I− in a structured clay loam soil under maize in a fi... more ABSTRACT Transport of radioactive iodide 131I− in a structured clay loam soil under maize in a final growing phase was monitored during five consecutive irrigation experiments under ponding. Each time, 27 mm of water were applied. The water of the second experiment was spiked with 200 MBq of 131I− tracer. Its activity was monitored as functions of depth and time with Geiger–M¨uller (G–M) detectors in 11 vertically installed access tubes. The aim of the study was to widen our current knowledge of water and solute transport in unsaturated soil under different agriculturally cultivated settings. It was supposed that the change in 131I− activity (or counting rate) is proportional to the change in soil water content. Rapid increase followed by a gradual decrease in 131I− activity occurred at all depths and was attributed to preferential flow. The iodide transport through structured soil profile was simulated by the HYDRUS 1D model. The model predicted relatively deep percolation of iodide within a short time, in a good agreement with the observed vertical iodide distribution in soil. We found that the top 30 cm of the soil profile is the most vulnerable layer in terms of water and solute movement, which is the same depth where the root structure of maize can extend.
Water Resources Research, 2002
Vadose Zone Journal, 2011
Due to the heterogeneity of soil hydraulic properties, there are many ways in which natural soils... more Due to the heterogeneity of soil hydraulic properties, there are many ways in which natural soils respond to rainfall, making upscaling of flow processes from plot to catchment scale difficult. The objectives of this study were to qualitatively characterize the flow pathways on forest and grassland hillslopes and to quantitatively define the relevant parameters controlling surface runoff generation by using infiltration and dye tracer experiments supplemented with measurements of the saturated hydraulic conductivity K sat , the structural porosity n SP , and the pore-size distribution PSD. While infiltration excess overland flow dominates in grassland, forest soil structure characterized by relatively high values of K sat and n SP enhances the infiltrability of the soil and consequently prevents or at least reduces surface runoff. The dye patterns suggest that macropores are more efficient in forest than in grassland soil. The low efficiency of grassland soil macropores in transporting all water vertically downward can be explained by (i) the fine and dense few topsoil layers caused by the land use that limit water flux into the underlying macropores and (ii) their restricted number, their tortuosity, and the restricted interaction between macropores and the matrix below the topsoil layer. The larger root water uptake of forest soil as compared to grassland soil can be viewed as an additional factor enhancing its storage capacity and, consequently, may reduce the generation of surface runoff. It remains unclear, however, what effect the low interaction between macropores and soil matrix in the upper part of the subsoil has on surface runoff in grassland soil; this should be investigated in future studies.
Soil and Tillage Research, 2011
Hydrology and Earth System Sciences, 1997
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Papers by Abdallah Alaoui