Aurore Degré

Conventional versus alternative pig production assessed by multicriteria decision analysis

Differentiated quality and respect for the environment seem to be linked implicitly, but there is no demonstration of this concept for pig production. Pig production takes on different forms. Conventional pig production occurs side by side with some productions of “differentiated qualities” that are encouraged by the European Union as well as by nations. At the same time, the EU and nations are imposing environmental limitations concerning, for instance, the management of nitrogen and respect for neighbours. Here, we compared environmental impacts of 3 types of production: conventional production, organic production and free-range production. We took into account the process performances of 21 farms in the Walloon Region, Belgium. We compared the global process performances by multicriteria analysis. A jury of 16 experts was questioned to assign a relative importance to the emissions of ammonia, greenhouse gases, molecular nitrogen, odour and nitrogen to effluents. We found that the highest weighting was assigned to the N content of effluents, then to odour diffusion, the emission of ammonia, the emissions of greenhouse gas and finally, the emission of molecular nitrogen got a weak weighting. Our results showed that the relative ordering obtained was: (1) free-range production, (2) organic production and (3) conventional production. Nevertheless, within every sample a significant variability in the performances was observed. The same method applied within every sample enabled the creation of sub-groups. After reordering, we found that the most effective farms of every system of production were classified as top of the class. Thus, our original approach showed that on average the production of differentiated qualities was more environmentally effective than the conventional production. However, the variability of the performances within a system of production was high and it was quite possible for the conventional farms to reach results comparable with those of the best organic and free-range operations.

Soil-specific calibration of capacitance sensors considering clay content and bulk density

Soil hydrology research requires the accurate measurement of soil water content. Recently, less expensive capacitance sensors (CS) have become popular for the measurement of soil moisture across soil profiles, but these sensors need to be calibrated for precise results. The purpose of the present study was to determine the effect of clay content and bulk density (ρb) on the calibration of CS. Two different CS (10HS and 5TM) were considered for the study. Clay content and ρb of the soils were determined from two different sites and from three different depths (0–5, 25–30 and 50–60 cm) of an experimental field in Gembloux, Belgium. Custom calibration (CC) equations were developed using packed soil columns following the same ρb at sequential volumetric water content (θ) levels. The factory-supplied calibration (FSC) showed an overestimation of θ (0.04–0.07 m3 m–3) with the 10HS sensor, and an underestimation of θ (0.06–0.077 m3 m–3) with the 5TM sensor for the entire calibration range. The variance in raw sensor outputs for different ρb and clay content of soil depths was not highly significant because the soil had limited range of variability in ρb and clay content. However, the CC is recommended in parallel with FSC for the precise measurement of soil moisture with CS.

How pixel size affects a sediment connectivity index in central Belgium

Connectivity has become an increasingly used concept in hydrological and sediment research. In order to quantify it, various indices have been proposed since the start of the 21st century including the index of connectivity. This index is based on a limited number of factors, the most important one being topography. Sediment connectivity indices values probably depend on the digital elevation model (DEM) resolution. The aim of this study was, first, to compare the effect of DEM pixel size (between 0.25 and 10m, using an UAV) in the Belgian loess belt, a lowland area. We show that the index values were lower when the pixel size decreased (a difference of about 20% in value between 0.25 and 10m). In addition, the impact of linear features in the watershed (e.g. grass strip, bank and road) was lower with the largest pixel sizes, and the connectivity pattern was affected with a pixel size of 5m or more. At lower pixel sizes (1m or below), some more disconnected regions appeared. These corresponded with zones where there had been water stagnation during and after rainfalls, and was corroborated by field observations. This confirmed the need for a proper resolution according to the objectives of the study. The second aim of this study was to deduce a minimum pixel size for connectivity study, helping local erosion or sedimentation location and consequent land management decisions. In our context, 1m stands as the optimum DEM resolution. This pixel size permitted location of all ‘key areas’ in terms of erosion. Very high resolutions (<0.5m) did not generate much more information, and their calculation time was far greater. Copyright

Can the pore scale geometry explain soil sample scale hydrodynamic properties

For decades, the development of new visualization techniques has brought incredible insights into our understanding of how soil structure affects soil function. X-ray microtomography is a technique often used by soil scientists but challenges remain with the implementation of the procedure, including how well the samples represent the uniqueness of the pore network and structure and the systemic compromise between sample size and resolution. We, therefore, chose to study soil samples from two perspectives: a macroscopic scale with hydrodynamic characterization and a microscopic scale with structural characterization through the use of X-ray microtomography (X-ray µCT) at a voxel size of 21.5³ µm³ (resampled at 43³ µm³). The objective of this paper is to unravel the relationships between macroscopic soil properties and microscopic soil structure. The twenty-four samples came from an agricultural field (Cutanic Luvisol) and the macroscopic hydrodynamic properties were determined using laboratory measurements of the saturated hydraulic conductivity (Ks), air permeability (ka), and retention curves (SWRC). The X-ray µCT images were segmented using a global method and multiple microscopic measurements were calculated. We used Bayesian statistics to report the credible correlation coefficients and linear regressions models between macro- and microscopic measurements. Due to the small voxel size, we observed unprecedented relationships, such as positive correlations between log(Ks) and a µCT global connectivity indicator, the fractal dimension of the µCT images or the µCT degree of anisotropy. The air permeability measured at a water matric potential of -70 kPa was correlated to the average coordination number and the X-ray µCT porosity, but was best explained by the average pore volume of the smallest pores. Continuous SWRC were better predicted near saturation when the pore-size distributions calculated on the X-ray µCT images were used as model input. We also showed a link between pores of different sizes. Identifying the key geometrical indicators that induce soil hydrodynamic behavior is of major interest for the generation of phenomenological pore network models. These models are useful to test physical equations of fluid transport that ultimately depend on a multitude of processes, and induce numerous biological processes.

International assessment of future low flow regimes and their impact on three water related sectors in the Meuse basin – a collaborative approach

ABSTRACT There is a wide recognition of the watershed scale as the right scale for global water management, notably in the context of the water framework directive. Hence, it often refers to international management and therefore to various pre-existing regional management tools, models or even objectives. In this study, we aim at describing the collaborative assessment of climate changes effect on low-flow regime and the consequences on three water-related sectors: drinking water production, agriculture and electricity production. The paper highlights the choices that were made during the study that involved scientific teams, managers and stakeholders from the four main countries of the Meuse Basin. It shows that the methodological choices were operational and aimed at preserving existing methods and knowledge within each country. They led to hydrological scenarios comparable to the main available ensemble approaches and to methodologies well accepted within the concerned countries. The results of the project highlight and quantify the water scarcity that the three sectors will have to face by the end of the century mainly regarding the electricity production. They also show that common allocation rules are necessary to manage water demand during future low-flow periods.

Distribution des propriétés morphologiques et chimiques d’un sol le long d’un versant forestier

Dans la région ardennaise, la plupart des zones boisées se trouvent sur des terrains dont la pente est relativement importante. La productivité d’une parcelle forestière étant au centre des préoccupations des sylviculteurs, il est intéressant de connaître exactement les paramètres qui peuvent l’influencer et leur évolution le long d’un versant, qu’ils soient du domaine de l’hydrologie, de la pédologie ou autre.