Evaluation of the space-time variability of soil salinity by statistical, geostatistical and bayesian maximum entropy methods

This thesis aims to the development of statistical and geostatistical methods for the analysis of space time data and their application to soil salinity. Special emphasis was put on how to characterize soil salinity. Also, the focus was on three groups of methods, i.e. statistical, geostatistical and Bayesian maximum entropy (BME) approaches. Although, the methods were applied to soil salinity, they can be applied to other fields of research as well. In summary, the two main objectives of this study were: - monitoring the temporal change of the spatial pattern of soil salinity using classical statistical methods; - mapping of soil salinity at unobserved space locations and time instants using classical and modern geostatistical methods like the BME

Effect of tillage practices on the soil carbon dioxide flux during fall and spring seasons in a Mediterranean Vertisol

In this study, we assessed the effect of conventional tillage (CT), reduced (RT) and no tillage (NT) practices on the soil CO2 flux of a Mediterranean Vertisol in semi-arid Morocco. The measurements focused on the short term (0 to 96 h) soil CO2 fluxes measured directly after tillage during the fall and spring period. Soil temperature, moisture and soil strength were measured congruently to study their effect on the soil CO2 flux magnitude. Immediately after fall tillage, the CT showed the highest CO2 flux (4.9 g m-2 h-1); RT exhibited an intermediate value (2.1 g m-2 h-1) whereas the lowest flux (0.7 g m-2 h-1) was reported under NT. After spring tillage, similar but smaller impacts of the tillage practices on soil CO2 flux were reported with fluxes ranging from 1.8 g CO2 m-2 h-1 (CT) to less than 0.1 g CO2 m-2 h-1 (NT). Soil strength was significantly correlated with soil CO2 emission; whereas surface soil temperature and moisture were low correlated to the soil CO2 flux. The intensity of rainfall events before fall and spring tillage practices could explain the seasonal CO2 flux trends. The findings promote conservation tillage and more specifically no tillage practices to reduce CO2 losses within these Mediterranean agroecosystems. (Résumé d'auteur

Improving Groat Β-Glucan Content of Developed Hexaploid Oat Lines Derivative of Interspecific Crosses

Oat grains, untapped reservoir of nutrients and phytochemicals, are very beneficial for food and feed. β-glucan content of sixteen derivative hexaploid lines, derivative of interspecific crosses between two tetraploid oat species A. magna and/or A. murphyi with five Moroccan hexaploid oat cultivars of A. sativa, aiming the improvement of their groat nutritive value, was accurately assessed. The new developed lines as well as their hexaploid oat parents were tested for agronomic performance under Moroccan climatic conditions in two different locations. Groat’s composition analysis has revealed that β-glucan content ranged from 1,37% to 6,05%. Significant β-glucan contents were detected for the cultivar Zahri (6,05±1,19) followed by the lines A. magna F11-4 (magxsat) (5,77±0,20)%, F11-5 (magxsat) (5,79±0,31)%, and F11-8 (magxsat) (5,55±0,41)%. The obtained results indicated that these lines are very promising. Furthermore, substantial differences among cultivars and lines over locations were observed and therefore, the genetic variability, the environmental conditions and their interaction has exerted statistically high significant effects on the groat β-glucan content (p < 0,0001). Thus, four among sixteen assessed lines which present high β-glucan content could be conceived for human consumption. These results confirm the success of acheived crosses and enhances the valorization of oats owing to its high content in β-glucans and other nutraceutical substances. Keywords: Oat, β-glucan content, tetraploid oat, A. magna, A. murphyi, hexaploid oat, A. sativa, genotype x environmental conditions

Suivi De La Cinétique Du Développement Racinaire Des Plantes Destinées A La Stabilisation Des Talus Marneux De L’axe Autoroutier Fès-Taza (Nord Du Maroc)

Le passage de l’autoroute Fès-Taza (Maroc) à travers des substrats marneux a engendré des talus particulièrement sensibles à l’érosion hydrique. En effet, sitôt confectionnés, ces talus subissent différentes formes d’érosion avec des sévérités variant avec l’intensité des pluies. Vu que la stabilisation mécanique s’est révélée difficile et trop coûteuse, les auteurs ont envisagé de faire appel au génie biologique mettant en œuvre les plantes qui contribuent au maintien du sol grâce à leur système racinaire. Ce travail concerne l’évaluation de l’effet, sur la stabilité du sol, de plusieurs espèces végétales plantées sur des talus marneux de l’axe autoroutier Fès-Taza. Des espèces prometteuses ont fait l’objet d’un suivi sous conditions contrôlées pour mieux comprendre la cinétique du développement de leurs racines. Il s’agit de: Acacia cyanophylla, Arundo donax, Medicago arborea, Prosopis pubescens, Retama monosperma et Spartium junceum. Ce suivi a été réalisé sur un substrat prélevé à partir des talus marneux de l’autoroute Fès-Taza et mis dans des mini-rhizotrons pour suivre la croissance et l’architecture du système racinaire. Acacia cyanophylla et Arundo donax, sont les espèces qui ont montré les densités racinaires les plus élevées. Medicago arborea est l’espèce qui a enregistré la vitesse moyenne d’allongement racinaire maximale parmi les espèces testées (9,3 cm/mois). Ces six espèces ont montré des caractéristiques complémentaires nécessaires au maintien des talus. On les recommande comme composition floristique dans des conditions similaires

SEASONAL VARIATION OF HEAVY METAL POLLUTION OF GROUNDWATER AND SOIL IN THE M’NASRA REGION (GHARB, MOROCCO)

M’nasra region is well known for increasing levels of heavy metal pollution in the environment, mainly due to waste discharge of Ouled Berjal, the irrational use of fertilizers, and the discharge of waste from several industries. The objective of this study was to access the seasonal variations in the groundwater and soil quality with respect to heavy metal pollution. Water samples from wells and samples from soil near them were taken during wet (January - March 2017) and dry (July 2017) seasons and concentrations of Cd, Cu, Cr, Mn, Ni, Pb, and Zn were determined using an Atomic Absorption Spectrophotometer (AAS). Contamination factor for each heavy metal and Nemerow pollution index was calculated. Results of the study revealed a decrease in pollution degree from wet to dry for soil and an increase in the case of groundwater. Cu had the lowest and Ni had the highest concentration in irrigation water whereas, for soil, Cd had the lowest and Zn had the highest concentration. During the wet season, all the concentrations of heavy metals decreased compared to the dry season, this can be explained by the dilution of these concentrations by precipitation water and therefore to lower absorption of these heavy metals in the water of irrigations and/or soil. Vertical transfer of pollutants from topsoil to groundwater was assessed using Hierarchical Cluster Analysis to identify associations between heavy metals and soil texture. In the case of Ni and Cr, the variables corresponding to the concentrations from soil and groundwater were part of the same cluster, in both seasons, the distribution maps of concentrations confirmed the pattern of transfer. This study can be considered as a baseline for the seasonal variation of heavy metal pollution of groundwater and soil. This study can be used not only for monitoring the study area but also as a tool for the implementation of environmental protection policies

Soil salinity related to physical soil characteristics and irrigation management in four Mediterranean irrigation districts

25 Pag., 6 Tabl., 1 Fig. The definitive version is available at: http://www.sciencedirect.com/science/journal/03783774Irrigated agriculture is threatened by soil salinity in numerous arid and semiarid areas of the Mediterranean basin. The objective of this work was to quantify soil salinity through electromagnetic induction (EMI) techniques and relate it to the physical characteristics and irrigation management of four Mediterranean irrigation districts located in Morocco, Spain, Tunisia and Turkey. The volume and salinity of the main water inputs (irrigation and precipitation) and outputs (crop evapotranspiration and drainage) were measured or estimated in each district. Soil salinity (ECe) maps were obtained through electromagnetic induction surveys (ECa readings) and district-specific ECa–ECe calibrations. Gravimetric soil water content (WC) and soil saturation percentage (SP) were also measured in the soil calibration samples. The ECa–ECe calibration equations were highly significant (P 0.1) with WC, and was only significantly correlated (P Morocco (2.2 dS m−1) > Spain (1.4 dS m−1) > Turkey (0.45 dS m−1). Soil salinity was mainly affected by irrigation water salinity and irrigation efficiency. Drainage water salinity at the exit of each district was mostly affected by soil salinity and irrigation efficiency, with values very high in Tunisia (9.0 dS m−1), high in Spain (4.6 dS m−1), moderate in Morocco (estimated at 2.6 dS m−1), and low in Turkey (1.4 dS m−1). Salt loads in drainage waters, calculated from their salinity (ECdw) and volume (Q), were highest in Tunisia (very high Q and very high ECdw), intermediate in Turkey (extremely high Q and low ECdw) and lowest in Spain (very low Q and high ECdw) (there were no Q data for Morocco). Reduction of these high drainage volumes through sound irrigation management would be the most efficient way to control the off-site salt-pollution caused by these Mediterranean irrigation districts.This study was supported by the European Commission research project INCO-CT-2005-015031.Peer reviewe

Accumulation of Heavy Metals in Soils Irrigated by Treated Wastewater: A Case Study from the Northwest of the Haut Chelif Plain, Algeria

Long-term irrigation by treated wastewater (TWW) can lead to the accumulation of heavy metals (HM) in the soil inducing negative effects on the pedo-environment. In this study, plots irrigated with TWW were studied to estimate the accumulation trends of HM and their impact on the physicochemical properties of the soil over a period of four years under a gravity irrigation system on turf with no fertiliser input. Soil samples were taken at two depths (0 to 20 cm: H1 and 20 to 40 cm: H2). The results of this study show that TWW are a main source of increase in HM in the soil by well-identified conditions, the degradation of the environment in general and on the physicochemical quality of soils in particular. It was concluded that the use of TWW in long-term irrigation enriches the soils with heavy metals, by main factors such as TWW composition, climatic conditions, soil type, and irrigation frequency