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Physicochemical and Mineralogical Characterization of the Mediterranean Soils of Triffa Plain (Northeast of Morocco) by the Physicochemical Analysis, X-ray Diffraction and Vis-NIR Spectroscopy

Caractérisation physico-chimique et minéralogique des sols de la plaine des Triffa (Nord du Maroc) par l'utilisation des analyses physico-chimiques, Diffraction par rayon X et spectroscopie visible et proche infrarouge.

Abstract : The soils of the Mediterranean regions, characterized by summer aridity and the strong presence of limestone rocks, are dominated by the presence of calcium or even limestone. The soils of the Triffa plain, located in the northeastern part of Morocco, is a perfect example of the Mediterranean soils. This plain represents one of the most fertile agricultural zones in the northeastern of Morocco, where all cultivated lands are, dominated by high added values irrigated crops such as Citrus and vegetables. The knowledge of soil characteristics is an important task to better manage these crops. In this context, the main objectives of this study are twofold: 1) to determine the physicochemical proprieties of Triffa plain and their mineralogy using the X-ray diffraction and physicochemical laboratory analysis, and 2). to understand the information provided by the VIS-NIR spectroscopy as it relates to soil mineralogy. To reach these objectives, one hundred eighty-one soil samples were collected from the topsoil horizon (0-30cm) in the study area in 2018. These samples were then analyzed for texture, Organic Matter (OM), Calcium Carbonates (CaCO3), pH, electrical conductivity and potassium. The X-ray diffraction and VIS-NIR spectroscopy were used to determine the soil mineralogy. The results of the physicochemical analysis showed that the soils of the study area are generally belonged to the slightly to moderately calcareous soil classes in term of CaCO3 and are generally basic in term of pH. Concerning the soil organic matter (OM), the study area is characterized by low to medium values of OM content. The soil texture of Triffa plain is dominated by a silt-loam texture. The results of X-ray patterns indicate the dominance of the kaolinite, illite, vermiculite and chlorite, while the mineralogical associations are formed by complex mixtures of carbonates, gypsum, quartz, feldspars and goethite in variable proportions depending on the soil types. Mineralogical diagnostic of VIS-NIR spectroscopy data showed that the absorption bands centered on long waves of 450, 850, 1450, 1950, and 2200 nm are the best bands to be used to study soil mineralogy.