The simulation of multiphase fluid flow in the subsurface of soil requires that the pressure-saturation (P-S) relations of the porous medium be known for all fluid pairs. The objective of this study ...was 1) to develop a technique for routinely measuring the pressure-saturation (PS) curves of undisturbed soil samples saturated with NAPL 2) to build a database using the measured P-S curves and the physical, chemical properties of the soils; and 3) to establish the dependence of nonaqueous phase liquids (NAPL) retention on the other soil properties. The soils in this investigation were taken from 35 horizons of 12 soil profiles in Hungary. Undisturbed soil samples were collected from each horizon with a core sampler. The P-S curves with NAPL were determined by using a modified pressure cell apparatus, which was designed and constructed by our laboratory. Statistical analysis was performed involving selected soil parameters and the measured NAPL retention data. By the application of the linear regression equations, the NAPL retention curves can be calculated directly from the mechanical fractions, bulk density, and humus content values of the soil in question. The comparison of estimated and measured NAPL retention data demonstrates the improvement gained by using the regression approach instead of the Leverett type scaling method. The scaling method significantly underestimates the NAPL retention. The accuracy of this new estimation method (after extending the database) can be useful for modeling NAPL fate and migration or mapping the organic contaminant sensitivity of the soils.
Despite the increasing interest in applying composts as soil amendments worldwide, there is a lack of knowledge on short-term effects of compost amendments on soil structural and hydraulic ...properties. Our goal was to study the effect of compost and vermicompost-based soil amendments on soil structure, soil water retention characteristics, aggregate stability and plant water use efficiency compared to that of mineral fertilizers and food-waste digestate and examine if these effects are evident within a short time after application. We set up a pot experiment with spring wheat using a sandy and a loamy soil receiving either mineral fertilizer (MF); dewatered digestate from anaerobic digestion of food waste (DG), vermicomposted digestate (VC_DG); sewage sludge-based compost (C_SS) and sewage sludge-based vermicompost (VC_SS). We then monitored and calculated the soil water balance components (irrigation, outflow, evaporation, transpiration, and soil water content). At harvest, we measured shoot biomass, soil texture, bulk density, water retention characteristics and aggregate stability. The irrigation use efficiency (IE) and the plant water use efficiency (WUE) were calculated for each treatment by dividing the transpiration and the dry shoot biomass with the amount of water used for irrigation, respectively. For the sandy soil, we used X-Ray computed tomography to visualise the pore system after applying organic amendments and to derive metrics of the pore-network such as its fractal dimension, imaged macroporosity and critical pore diameter. X-Ray tomography indicated that composting and vermicomposting resulted in more complex and diverse porous system and increased soil macroporosity. The increased fractal dimensions also indicated that compost and vermicompost can contribute to structure formation and stabilization within a short time after their application. Despite the small application rate and short incubation time, the application of organic amendments to the two different soil types resulted in improved soil water holding capacity and water use efficiency. Composting and vermicomposting appeared to have the best effect at reducing the irrigation demand and evaporation losses and increasing the water use efficiency of the plant, likely through their effect on soil structure and the pore-size distribution.
Spatially explicit, quantitative information on soil hydraulic properties is required in various modelling schemes. At European scale, EU-SoilHydroGrids proved its applicability in a number of ...studies, in ecological predictions, geological and hydrological hazard assessment, agri-environmental models, among others. Inspired by its continental antecedent, an analogous, but larger scale, national, 3D soil hydraulic database was elaborated for the territory of Hungary (HU-SoilHydroGrids) supported by various improvements (i–iv) in the computation process. Pedotransfer functions (PTFs) were built in the form of i) advanced machine learning methods and ensemble models, and trained on the ii) national soil hydrophysical dataset. The set of predictors used in PTFs was supplemented by iii) additional environmental auxiliary variables. Spatial layers of the soil hydraulic parameters were generated using iv) 100 m resolution information on primary soil properties, namely DOSoReMI.hu. HU-SoilHydroGrids provides information on the most frequently required soil hydraulic properties (water content at saturation, field capacity and wilting point, saturated hydraulic conductivity and van Genuchten parameters for the description of the moisture retention curve) with national coverage at 100 m spatial resolution down to 2 m depth for six GSM standard depth layers. The HU-SoilHydroGrids has significantly lower squared error in the case of describing the moisture retention curve and hydraulic conductivity than the EU-SoilHydroGrids. The derived 3D soil hydraulic database (ver1.0) is presently available in National Laboratory for Water Science and Water Safety for project partners in order to test its functional performance in describing hydrological and ecological processes.
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•3D soil hydraulic database was derived for the territory of Hungary up to 2 m depth.•HU-SoilHydroGrids performs significantly better than EU-SoilHydroGrids.•PTFs were derived with four machine learning methods and four ensemble models.•Ensemble model performed better if only the best performing MLs were included.•The PTFs were applied on available environmental data to compute the maps.
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