Changes in alluvial soil quality under long-term irrigation with two marginal water sources in an arid environment

Abstract

Soil is one of the most vital natural resources affecting human life (Iscan and Guler, 2021). It contributes to ecosystem services through several functions, including biomass production, improving ground and surface water quality, carbon capture for climate mitigation, limiting emissions of the greenhouse gas, and biodiversity protection and enhancement (Chalhoub et al., 2020). The term “soil quality”is a concept describing soil competence to perform those functions. Thus, securing soil quality is essential for future planning due to its importance in achieving land-related sustainable development goals (Bouma, 2020). In Egypt, the total cultivated area is 3.6 million ha, of which 89% are alluvial soils in the Nile Valley (43%) and Delta (65%)(Mohamed, 2019). However, water availability remains the major constraint for sustainable agricultural production (Zohry and Ouda, 2020). Egypt is one of the most arid regions of the world, where nearly 86% of its total land is hyper-arid and 14% is arid and semiarid (Embabi, 2020). Thus, the country depends entirely on irrigated agriculture which consumes more than 85% of the available freshwater (Abdelhafez et al., 2020). This accelerates the dependence on alternative water sources in irrigation, including agricultural drainage water and treated sewage water (Elbana et al., 2019; Bassouny et al., 2020; Farid et al., 2020) T CURRENT work aimed at verifying the modifications in chemical, physical, fertility, and environmental quality of alluvial soils south east of the Nile Delta of Egypt following 25-years irrigation using two marginal water sources; agricultural drainage water (ADW) and sewage effluent water (SEW). Two sites irrigated with ADW and SEW were chosen and compared with a nearby site irrigated with the Nile freshwater. At each site, ten samples of irrigation water and adjacent (around 50m) top soil (0 – 30 cm) were collected and analyzed. Marginal water irrigation caused slight changes in soil properties. The soil chemical quality index was adversely affected through increasing the pH, electrical conductivity, and exchangeable sodium percentage. Available micro-nutrients (Fe, Mn, Zn, and Cu) and P in SEW-irrigated soils were increased. The physical quality index was also increased, but mainly due to inherent soil properties (particle size distribution) rather than irrigation water. Parent materials governed soil total contents of Cr, Co and Ni, while contents of Cd, Cu, Pb, and Zn were closely related to irrigation water. The environmental quality index showed increasing trend in the ADW-irrigated soils, while a decrease in the SEW-irrigated soils. The marginal water irrigation resulted in positive changes in soil quality index exhibiting increases of 14 and 21% in the ADWand SEW-irrigated soils over the Nile freshwater-irrigated soils, respectively. It is recommended to perform periodic monitoring for irrigation water and soil quality in the studied area. Proper in-situ remediation scenarios and on-farm practices should be considered in future management.