Treated wastewater irrigation supports canola (Brassica napus L.) production in arid agroecosystems without exceeding soil salinity limits

Increasing freshwater scarcity and salinity risks in arid regions worldwide necessitate alternative water sources and salt-tolerant crops for sustainable agriculture. However, the effects of such water sources on crop performance and root-zone soil salinity need to be evaluated before advocating the wider use of saline water. This two-year field study used a split plot design to evaluate the effects of saline municipal treated wastewater (TWW) and freshwater (FW, control) (main-plot factor) on the performance of three spring canola ( Brassica napus L.) cultivars (CP930RR, CP955RR, and CP9978TF, subplot factor), and root-zone soil salinity (top 0.6 m). Results indicated that canola seed and straw yields did not differ significantly between TWW and FW across three cultivars. Across treatments, seed yield ranged from 2327 kg ha −1 under FW to 2675 kg ha −1 under TWW for CP9978TF, while the straw yield ranged from 5095 kg ha −1 for CP955RR under TWW to 6471 kg ha −1 for CP930RR under TWW. After two growing seasons, average soil salinity (ECe) increased from a baseline level of 2.3 dS m −1 to 3.5 dS m −1 under FW and 4.6 dS m −1 under TWW, while SAR rose from 4.2 to 5.2 and 7.5, respectively. Despite these increases, ECe and SAR remained well below canola thresholds for salinity (9.7 dS m −1 ) and sodicity (SAR 13). Salinity and sodicity increased with time and depth, particularly under TWW, indicating progressive salt accumulation and redistribution within the soil profile. The findings demonstrated that saline alternative water sources, particularly treated wastewater (TWW), can supplement or partially replace conventional freshwater irrigation and thereby contribute to the sustainability and resilience of irrigated agriculture in water-scarce regions.