Extraction and characterization of humic substances in soils of the irrigatedperimeter of Doukkala in Morocco [Extraction et caractérisation des substances humiques des sols du périmetre irrigué des Doukkala au Maroc]

This study consists in extracting and characterizing humic substances that make upthe soil organic matter. it was conducted on soils with contrasting and representative characters of the irrigated perimeter of doukkala (vertisol - isohumic - fersiallitic - immature).among the threehumic compoundsof the four soilsstudied,humin is the most predominant component,followed by humic and fulvic acids. carbon rate of these three humic fractions is high in the vertisol,medium in the isohumicsoil and the immature soil and low in the fersialliticone. this rate varies depending on the depth. the carbon content of the humic acid fraction and the humin decrease with the soil depth while the carbon content of the fulvic acid fraction is stable along the profile. according to elemental analysis,the low ratio ah / af and infraredspectroscopy,the humic acids of the studied soils are polymerized and have functional groups that confirm the nature of humic extracts samples.