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Groundwater resources in southwestern Tunisia are facing serious quantity and quality degradation. Given that they are the only source used for oasis irrigation, serious impacts on the soil of the region are expected. Accordingly, the main objective of this study is to evaluate the suitability of the sampled water from the Complex Terminal aquifer for irrigation purposes and to determine the potential impacts of their long-term use within the present agricultural practices on soil properties. The calculated ionic ratios indicate different classes ranging from permissible to unsuitable waters with respect to alkalinity standards (sodium adsorption ratio from 3.68 to 9.34, %Na from 36.7 to 61.2, and rill erodibility from 0.48 to 1.43). Water samples present high values of electrical conductivity, total dissolved solids, and potential salinity, about 54.5, 29.4, and 32.2%, respectively, which indicates serious salinity hazard. All the sampled waters may induce corrosion and clogging problems as deduced from the calculated light dynamic penetrometer and total hardness indices. The weighted water quality indices results (Canadian Water Quality Index and the irrigation water quality index) confirm the poor quality of the used irrigation water. The results of this study coupled with field investigations indicate that the cumulative impacts of low water quality and poor agricultural practices have damaged the total oasean ecosystem. K E Y W O R D S agricultural development, Complex Terminal, groundwater quality, land degradation, southern Tunisia oasis Résumé Les ressources en eau souterraine du sud-ouest de la Tunisie sont confrontées à une grave dégradation de la quantité et de la qualité. Étant donné qu'ils sont la seule source utilisée pour l'irrigation des oasis, de graves impacts sur le sol * Durabilité de l'agriculture dans les terres arides du sud de la Tunisie: impacts écologiques de la qualité de l'eau d'irrigation et des pratiques humaines

Given the aesthetic, cultural, ecological, and economic value of the date agro-system in Southwestern Tunisia, different management and conservation strategies have been warrantee to optimize land productivity sustainably. However, the inefficiency of the adopted management actions resulted in a continuous loss of soil fertility and decreasing fruit quality. Thus, the present paper attempts to evaluate accurately the evolution of the principal factors influencing date palm production and agricultural activities sustainability in the region. Integrated approaches of various irrigation water quality indices and geostatistical analysis coupled with field investigation and farming survey were applied to evaluate the evolution of key parameters influencing the development of date palm sustainably. The obtained results of the research indicate that the progressive land degradation is due to the effects of poorquality of water used for irrigation (EC between 674.4 and 5450 µs/cm, SAR exceeding locally 20 and about 80% of all the samples waters are of undoubtful quality according to the calculated indices), inappropriate irrigation scheduling (physiologic drought that might reach 3 months), traditional basin irrigation technique (decreasing of yield productivity, locally of 0.23, 0.23 and 0.25 kg m−3), an indigenous knowledge (sandy amendment, biologic compost, gravity improved irrigation…..). Also climate variability has leaded to furthermore degradation of crop quality. The degradation of date palm culture will be a great challenge for environmental conservation, food security and socio-economic values of the region unless a reasonable management take place, a flexible strategy based on indigenous knowledge of landowner, and scientific-based outlines with climate risks evaluation. The present paper might be useful to policy makers as a multi-disciplinary research covering most of the important aspects of date palm production.

The oasis soils of Tunisia face several climatic and soil constraints. Trying to have cultures that are profitable and beneficial in terms of soil C and N sequestration in such environments is already a challenge. To conduct this, we tested under identical conditions four types of occupation in sub-plots adjacent to the crops; barley alone, alfalfa alone, intercropping barley/alfalfa, and a control fallow in a saline gypseous desert soil poor in organic matter. Field experimentation was carried out in the oasis of Degache, which is very representative of other Tunisian oases. The stocks of C and N of the plot were calculated from the start in September 2019 before the installation of the different crops. After 21 months, the control plot shows a decrease of −41% in its stock of C and −25% in its stock N. However, the best result is that of the barley/alfalfa intercropping with an increase of +126.46% in the C stock and +178.67% in the N stock. After almost two years of experience, the beneficial effect of the intercropping system in the oasis is clear. These results are very motivating and seem to be a solution to the rapid decline in soil organic stocks.