Effects of Treated Wastewater Irrigation on Pastoral Plant Growth and Soil Properties in Al-Tamriat, Saudi Arabia

Water scarcity in arid regions has prompted the exploration of alternative irrigation sources, including treated wastewater, to support sustainable rangeland management. This study evaluated the effects of treated wastewater irrigation on the growth performance of native pastoral plants and soil chemical properties in the Al-Tamriat area, Al-Jouf, Saudi Arabia. Four native species—Traganum nudatum (Aldamran), Atriplex leucoclada (Alrughal), Salsola villosa (Al-Rutha), and Ziziphus nummularia (Sidir)—were cultivated under two irrigation regimes: normal water and treated wastewater. In a 12-month period, plant morphological traits (plant height, stem diameter, and canopy width) were monitored monthly, alongside soil chemical properties (pH, electrical conductivity, total organic carbon, organic matter, available phosphorus, exchangeable potassium, and available nitrogen) assessed at two soil depths (0–20 cm and 20–40 cm). Results showed species-specific responses to irrigation water quality where Atriplex leucoclada and Ziziphus nummularia exhibited superior growth performance (average heights of 54.78 cm and 53.09 cm, respectively), compared to the Traganum nudatum and Salsola villosa. Overall, normal water irrigation promoted greater plant growth (mean height: 36.61 cm) compared to treated wastewater (29.60 cm), likely due to salinity stress. In contrast, soil fertility improved under both treatments, with total organic carbon increasing from 0.08 to 0.43% in the top layer (0–20 cm) and from 0.05 to 0.40% in the bottom layer (20–40 cm) after 12 months of experimentation. Statistical analysis (ANOVA, p < 0.05) revealed significant interactive effects between water type, species, and time on plant and soil variables. These findings illustrate the potential of using TW for rangeland irrigation, while also illustrating its potential to limit growth in sensitive species. The results emphasize the importance of choosing the right species and managing water quality when developing TW irrigation plans for arid rangelands.