References of "Sirjacobs, Damien"
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See detailAirborne hyperspectral potential for coastal biogeochemistry of the Scheldt estuary and plume
Shimoni, Michal; Sirjacobs, Damien ULg; Borges, Alberto ULg et al

Conference (2003, May)

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See detailInfluence of the Aral Sea negative water balance on its seasonal circulation and ventilation patterns : use of a 3D hydrodynamic model
Sirjacobs, Damien ULg; Grégoire, Marilaure ULg; Delhez, Eric ULg et al

in Geophysical Research Abstracts (2003, April), 5(09052), 2003509052

Within the context of the EU INCO-COPERNICUS program "Desertification in the Aral Sea Region: A study of the Natural and Anthropogenic Impacts" (Contract IAC2-CT-2000-10023), a large-scale 3D hydrodynamic ... [more ▼]

Within the context of the EU INCO-COPERNICUS program "Desertification in the Aral Sea Region: A study of the Natural and Anthropogenic Impacts" (Contract IAC2-CT-2000-10023), a large-scale 3D hydrodynamic model was adapted to address specifically the macroscale processes affecting the Aral Sea water circulation and ventilation. The particular goal of this research is to simulate the effect of lasting negative water balance on the 3D seasonal circulation, temperature, salinity and water-mixing fields of the Aral Sea. The original Aral Sea seasonal hydrodynamism is simulated with the average seasonal forcings corresponding to the period from 1956 to 1960. This first investigation concerns a period of relative stability of the water balance, before the beginning of the drying process. The consequences of the drying process on the hydrodynamic of the Sea will be studied by comparing this first results with the simulation representing the average situation for the years 1981 to 1985, a very low river flow period. For both simulation periods, the forcing considered are the seasonal fluctuations of wind fields, precipitation, evaporation, river discharge and salinity, cloud cover, air temperature and humidity. The meteorological forcings were adapted to the common optimum one-month temporal resolution of the available data sets. Monthly mean kinetic energy flux and surface tensions were calculated from daily ECMWF wind data. Monthly in situ precipitation, surface air temperature and humidity fields were interpolated from data obtained from the Russian Hydrological and Meteorological Institute. Monthly water discharge and average salinity of the river water were considered for both Amu Darya and Syr Darya river over each simulation periods. The water mass conservation routines allowed the simulation of a changing coastline by taking into account local drying and flooding events of particular grid points. Preliminary barotropic runs were realised (for the 1951-1960 situation, before drying up began) in order to get a first experience of the behaviour of the hydrodynamic model. These first runs provide results about the evolution of the following state variables: elevation of the sea surface, 3D fields of vertical and horizontal flows, 2D fields of average horizontal flows and finally the 3D fields of turbulent kinetic energy. The mean seasonal salinity and temperature fields (in-situ data gathered by the Russian Hydrological and Meteorological Institute) are available for the two simulated periods and will allow a first validation of the hydrodynamic model. Various satellites products were identified, collected and processed in the frame of this research project and will be used for the validation of the model outputs. Seasonal level changes measurements derived from water table change will serve for water balance validation and sea surface temperature for hydrodynamics validation. [less ▲]

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See detailOn-line soil mechanical resistance mapping and correlation with soil physical properties for precision agriculture
Sirjacobs, Damien ULg; Hanquet, Bernard; Lebeau, Frédéric ULg et al

in Soil & Tillage Research (2002), 64

Measurement of local soil strength may be used for real time regulation of tillage parameters in precision agriculture. Cartography of soil physical properties will also facilitate the study of their ... [more ▼]

Measurement of local soil strength may be used for real time regulation of tillage parameters in precision agriculture. Cartography of soil physical properties will also facilitate the study of their influence on plant development and yields. The aim of this research was to develop and test in field conditions a sensor measuring on-line soil strength variations. The sensor was constituted of a thin blade pulled in the soil at constant depth and speed and a beam which transferred the soil–blade forces to a transducer fixed on the machine. This transducer measured the draft force (Fx), the vertical force (Fz) and the moment (My). A field experiment was performed in 2 ha field of silt soil (Hesbaye, Belgium). A soil strength map of the field was established by pulling the sensor at 5 m interline separation by a tractor equipped with a DGPS receiver. The relationship between the recorded forces and several soil physical parameters was studied by identifying 10 control plots on the sensor track. In each of them, cone index penetrometry profiles and soil water content were measured. Soil samples were taken in the centre of the plots to determine cohesion and internal friction angle, simple compression resistance, Atterberg limits, granulometry and pF curves. Triaxial tests identified over-consolidated soils in plots situated in the pounds of the field. Based on the parameters measured in the other plots, significant relationships were established between (1) a global penetrometry index and the Fx and My solicitations measured by the sensor; (2) gravimetric water content and the vertical force Fz. Interpolation by inverse distance with a range of 45 m gave the best result for the cartography of the three measured signals (Fx, Fz and My). The confrontation of those maps with pedological and topographic maps together with the statistical relationships and the farmer’s knowledge of the field showed high consistency. The results of this experiment in field conditions are encouraging and show the promising perspective of technological innovations allowing on-line characterisation of soil physical state for precision agriculture. [less ▲]

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See detailFlow interruption effects on intake rate and rill erosion in two soils
Sirjacobs, Damien ULg; Shainberg, Itzhak; Rapp, Ido et al

in Soil Science Society of America Journal (2001), 65

Efficiency of surface irrigation is often low because of poor infiltration uniformity, resulting from relatively long periods of infiltration at the upstream end and short periods of infiltration at the ... [more ▼]

Efficiency of surface irrigation is often low because of poor infiltration uniformity, resulting from relatively long periods of infiltration at the upstream end and short periods of infiltration at the downstream end of the field. Surge irrigation, the intermittent supply of water to furrows, generally reduces soil intake rate (IR) and improves moisture uniformity over the entire field. However, IR reduction varies from one irrigation scheme to another, depends on soil and water properties, and is difficult to predict. A laboratory study using miniflumes was designed to investigate the effect of interrupted flow on IR and soil loss from short rills. Two soils differing in their textures, a silt loam (Calcic Haploxeralf) derived from loess and a clay soil (Typic Haploxerert), were studied. Intake rate in the clay soil was greater than that in the silt loam. Therefore, different inflow rates were applied to the two soils to achieve similar runoff flow rates from the two soils. Cumulative infiltration decreased from 646 mL in continuous flow to 539 mL in interrupted flow for the silt loam and from 1142 to 1068 mL in the clay soil. Interrupted flow also reduced cumulative soil loss by 84% in the clay soil but had only a small effect on soil loss from the silt loam. However, when flow rate was increased from 80 to 320 mL min−1, interrupted flow reduced soil loss in the silt loam as much as in the clay soil. Consolidation of the soil surface and formation of cohesive forces between soil particles of the silt loam with unstable structure during flow interruption was suggested as the explanation for the effect of flow interruption on intake rate and soil detachment. These results need to be verified in field experiments. [less ▲]

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See detailA Soil Mechanical Resistance Sensor For On-Line Application In Precision Agriculture: Soil Strength Mapping And Correlation With Soil Physical Properties
Sirjacobs, Damien ULg; Destain, Marie-France ULg

in Proceedings of the 15th Conference of the International Soil Research Organization (I.S.T.R.O.) (2000, July)

Knowledge of local soil strength variation may permit variation of tillage parameters to produce a more optimal soil structure for root growth and plant development. Soil strength mapping can provide ... [more ▼]

Knowledge of local soil strength variation may permit variation of tillage parameters to produce a more optimal soil structure for root growth and plant development. Soil strength mapping can provide another layer of information in precision agriculture. The aim of this research is to develop a sensor able to measure on-line the local soil strength variations. This sensor is designed as follows: a thin blade penetrates the soil to a specific depth while the machine is moving, a beam transfers the soil-blade forces to a transducer fixed on the machine. The transducer measures then the horizontal and vertical forces and the moment. This paper describes a field experiment performed in a 2 ha field of silt soil (Hesbaye, Belgium). The first objective of this research is to establish a map of soil strength variability of the field. For this purpose, the sensor is pulled through the soil in parallel traverses at 5 m separation by a tractor equiped with a DGPS receiver. The second objective of the experiment is to study relation between measured forces and several measured soil physical parameters. Ten homogeneous plots where identified on the sensor track in order to cover as completely as possible the diversity of soil physical conditions encountered. On the median line of each of those plots, 10 Cone Index penetrometry profiles were measured with a mobile automated penetrometer recorder, soil water content was measured in 5 points, ans soil samples were taken in the center of the plot to determine the following parameters: cohesion and internal friction angle, simple compression resistance, Atterberg's limits, granulometry and pF curves. This experiment allowed the first identification of different soil strength areas in the field investigated. [less ▲]

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See detailLa résistance mécanique du sol: mesure en continu et cartographie pour l’agriculture de précision
Sirjacobs, Damien ULg; Destain, Marie-France ULg

in Zwaenepoel, Philippe (Ed.) Agriculture de Précision - Avancées de la recherche technologique et industrielle (2000, May)

La résistance mécanique d'un sol est un paramètre important qui conditionne la croissance racinaire et le développement des plantes. L'objectif de cette recherche est de mettre au point un capteur capable ... [more ▼]

La résistance mécanique d'un sol est un paramètre important qui conditionne la croissance racinaire et le développement des plantes. L'objectif de cette recherche est de mettre au point un capteur capable de mesurer en ligne les variations locales de résistance du sol. Celui-ci est constitué d'un anneau dynamométrique qui enregistre automatiquement les sollicitations (forces horizontales, verticales et couple) générées par la traction uniforme d'un lame dans le sol. Une première expérience a été menée dans un champ limoneux situé en Hesbaye (Belgique). Le géocodage de ces informations via un système DGPS a permis d'identifier des zones de diverses résistance au sein de la parcelle étudiée. [less ▲]

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See detailPAM, sediments, and interrupted flow effects on rill erosion and Intake rate
Sirjacobs, Damien ULg; Shainberg, Itzhak; Rapp, Iddo et al

in Soil Science Society of America Journal (2000), 64

The reduction in the intake rate (IR) during interrupted irrigation is difficult to predict. Sediments in irrigation water decrease the effect of interrupted irrigation on IR. Polyacrylamide (PAM) reduces ... [more ▼]

The reduction in the intake rate (IR) during interrupted irrigation is difficult to predict. Sediments in irrigation water decrease the effect of interrupted irrigation on IR. Polyacrylamide (PAM) reduces rill erosion, but its effect on IR is controversial. The effects of water quality (tap water, tap water containing sediments, and 10 g m−3 PAM solution) and interrupted flow on IR and rill erosion in an Alfisol (Calcic Haploxeralf) and a Vertisol (Typic Chromoxerert) were studied using laboratory miniflumes. Rill erosion in both soils was eliminated by the PAM treatment in both continuous and interrupted flow. The PAM application reduced IR in the Alfisol and increased it in the Vertisol. In the Alfisol, interrupted flow reduced IR of the PAM solution by 37% compared with only 18% for tap water. In the Vertisol, interrupted flow reduced IR only slightly and the decrease was not affected by the polymer. When the water contained sediments, cumulative infiltration was reduced by 22% for the Vertisol and 59% for the Alfisol in comparison with tap water. These reductions were attributed to depositional seal formation. The IR of the Alfisol was more susceptible to depositional seal formation than the Vertisol. The presence of sediments in water was effective in reducing rill erosion. The effects of interrupted flow with PAM on reducing IR were explained by partial blocking of the conducting pores leading to greater suction and compaction of the soil surface. For sediment-laden irrigation water, interrupted flow had no advantage over continuous flow in reducing IR because of depositional seal formation associated with the sediments in the water. [less ▲]

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