104 research outputs found
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 Î-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. ÎČ-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. Groatâs composition analysis has revealed that ÎČ-glucan content ranged from 1,37% to 6,05%. Significant ÎČ-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 ÎČ-glucan content (p < 0,0001). Thus, four among sixteen assessed lines which present high ÎČ-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 ÎČ-glucans and other nutraceutical substances. Keywords: Oat, ÎČ-glucan content, tetraploid oat, A. magna, A. murphyi, hexaploid oat, A. sativa, genotype x environmental conditions
Suivi De La CinĂ©tique Du DĂ©veloppement Racinaire Des Plantes DestinĂ©es A La Stabilisation Des Talus Marneux De Lâaxe Autoroutier FĂšs-Taza (Nord Du Maroc)
Le passage de lâautoroute FĂšs-Taza (Maroc) Ă travers des substrats marneux a engendrĂ© des talus particuliĂšrement sensibles Ă lâĂ©rosion hydrique. En effet, sitĂŽt confectionnĂ©s, ces talus subissent diffĂ©rentes formes dâĂ©rosion avec des sĂ©vĂ©ritĂ©s variant avec lâintensitĂ© des pluies. Vu que la stabilisation mĂ©canique sâest rĂ©vĂ©lĂ©e difficile et trop coĂ»teuse, les auteurs ont envisagĂ© de faire appel au gĂ©nie biologique mettant en Ćuvre les plantes qui contribuent au maintien du sol grĂące Ă leur systĂšme racinaire. Ce travail concerne lâĂ©valuation de lâeffet, sur la stabilitĂ© du sol, de plusieurs espĂšces vĂ©gĂ©tales plantĂ©es sur des talus marneux de lâaxe autoroutier FĂšs-Taza. Des espĂšces prometteuses ont fait lâobjet dâun suivi sous conditions contrĂŽlĂ©es pour mieux comprendre la cinĂ©tique du dĂ©veloppement de leurs racines. Il sâagit de: Acacia cyanophylla, Arundo donax, Medicago arborea, Prosopis pubescens, Retama monosperma et Spartium junceum. Ce suivi a Ă©tĂ© rĂ©alisĂ© sur un substrat prĂ©levĂ© Ă partir des talus marneux de lâautoroute FĂšs-Taza et mis dans des mini-rhizotrons pour suivre la croissance et lâarchitecture du systĂšme racinaire. Acacia cyanophylla et Arundo donax, sont les espĂšces qui ont montrĂ© les densitĂ©s racinaires les plus Ă©levĂ©es. Medicago arborea est lâespĂšce qui a enregistrĂ© la vitesse moyenne dâallongement racinaire maximale parmi les espĂšces testĂ©es (9,3 cm/mois). Ces six espĂšces ont montrĂ© des caractĂ©ristiques complĂ©mentaires nĂ©cessaires 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 MâNASRA REGION (GHARB, MOROCCO)
Mânasra 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 ECaâECe calibrations. Gravimetric soil water content (WC) and soil saturation percentage (SP) were also measured in the soil calibration samples. The ECaâECe calibration equations were highly significant (P 0.1) with WC, and was only significantly correlated (P Morocco (2.2 dS mâ1) > Spain (1.4 dS mâ1) > Turkey (0.45 dS mâ1). 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 mâ1), high in Spain (4.6 dS mâ1), moderate in Morocco (estimated at 2.6 dS mâ1), and low in Turkey (1.4 dS mâ1). 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 20Â cm: H1 and 20 to 40Â 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
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