Impact de l’irrigation sur la distribution spatiale du carbone organique dans les sols d’une palmerie dans la région de Ghardaïa (cas d’El-Atteuf)

Abstract

Soil organic matter plays a fundamental role in fertility, structural stability, and water retention, especially in arid regions where it is essential for the sustainability of agricultural systems. This study was conducted in the vicinity of the El-Ahbass Dam in El-Atteuf (Ghardaïa, southern Algeria), an oasis area characterized by an arid climate and soils low in organic carbon, irrigated using a traditional system. The main objective of this study was to evaluate the impact of irrigation on soil organic carbon (SOC) and selected physicochemical properties. To this end, 80 soil samples were collected around 40 palm trees at a depth of 0–30 cm, both before and after irrigation. The analysis of physicochemical parameters to assess the quality of irrigation water revealed that the groundwater is neutral to slightly alkaline (pH 7.2), but exhibits high salinity (EC = 6.06 dS/m), which may pose problems for irrigation, particularly for salt-sensitive crops. A Sodium Adsorption Ratio (SAR) of 4.24 indicates a moderate risk of soil sodification. The results showed an increase in SOC content in several irrigated areas, reaching up to 1.13%, especially beneath palm trees where moisture and organic residues accumulate. The soils are generally alkaline, with a pH ranging from 8 to 9, and showed an increase in electrical conductivity (from 0.2 to 0.31 dS/m), indicating salt buildup following irrigation. Spatial analysis revealed a redistribution of SOC: losses were observed in areas near the well and on sloping land, particularly from the northwest toward the south, due to surface runoff, while higher concentrations were found in lower-lying areas. These findings confirm that irrigation, while enhancing moisture and biological activity locally, can also result in carbon leaching depending on topography and runoff dynamics. The study underscores the importance of integrated water and organic matter management in arid regions to maintain soil quality and support long-term resilience.