Agricultural residues are generated during the production and processing of agricultural crops. Under modern date palm plantation practices, field operations generate huge quantities of residues, which are discarded with little valorization. The date palm agro-industry produces significant amounts of waste. The accumulation of these residues can cause ecological damage to the oasis ecosystems. There is a lack of comprehensive data on long-term research studies that aim to assess the impact of date palm waste management practices. Composting and/or pyrolysis of date palm residues showed benefits for improving soil physical and chemical properties, particularly in sandy soils. This claim holds particular significance for arid and semi-arid regions, which are characterized by low fertility and are susceptible to soil degradation, accentuated by ongoing climate change. This review summarizes the existing literature concerning the valorization of date palm residues with regards to compost and pyrolysis processes, as well as the impact of their application on soil quality. Further research is required to assess the effects of using date palm residues for better soil amendment management. Research should focus on composting and biochar technologies for date palm residues and their application in arid and semi-arid regions to combat soil erosion and degradation. Increasing the beneficial uses of date palm residues could lead to sustainable and economic growth in dry areas.

Generally, soils of arid and semi-arid regions have low water retention properties due to high sand and low organic carbon contents. This study aimed at quantifying the effect of date palm-based organic amendments (OAs) on the water retention properties of two soils (sandy loam and silty loam), as well as the influence of sand supplementation (0.5–2 mm) on the magnitude of the effect of OAs. Different grain size distributions were obtained by adding sand to natural soils. For this purpose, sand was added to the two soils (1/3 and 2/3) and different soil-OA combinations were tested at a dose of 3% by mass: compost alone, biochar alone and a mixture of biochar and compost (50:50 in mass), in addition to unamended control soils. Soil water contents were measured at nine matric potentials ranging from the saturation to the permanent wilting point. Biochar was more efficient than compost at improving soil water retention. The effect of organic amendments on water retention increased with sand content. In most cases, soil water content values were significantly higher for biochar-amended soils than for unamended or compost-amended soils. The weakness of the effect of compost addition (if alone) was probably due to its properties and notably its high mineral content and electrical conductivity. Soil sand supplementation led to higher differences between the OA-amended soils and unamended soils. Changes in available water capacity reached +26% and +80% in a sandy loamy soil enriched with 2/3 sand and amended with compost and with biochar, respectively, compared to the unamended soil. These results show that sand content (and more generally, soil texture) influences the effect of OA application. Thus, the application of biochar from date palm residues in soil seems to be an effective solution to improve the water retention properties of coarse textured soils and contribute to optimizing the use of water resources in irrigated areas.

The Kara River watershed (KRW), northern Togo, is facing climate-change impacts that have never been clearly characterized. Six decades of rainfall data (1961–2020) from six measuring stations ideally distributed across the watershed were used in this study. The flow records from two stations situated in contrasting locations on the KRW were also used. Statistical tests were conducted to assess the spatial and temporal variability of the rainfall and to detect tendencies within these meteorological series. The water balance method and calculation of the dry-off coefficient and of the groundwater volume drained by rivers allowed evaluating the impact of climatic evolution on surface flow and on groundwater volumes during the six decades studied. The results showed contrasting spatiotemporal variability of rainfall (and of aquifer recharge) over the watershed with a decreasing tendency upstream and an increasing one downstream. At the same time, the water volume drained by the aquifer to sustain the river’s base flow decreased from −22% to −36% depending on the measuring station. These results constitute a decision-making tool for Togolese water resource managers and are of primary importance for characterizing the fate of water resources worldwide in regions subject to severe droughts.