To address the imbalance between the supply and demand of water resources and compensate for the shortage of freshwater resources, the use of brackish and saline water for irrigation has become crucial. Simultaneously, the effects of different sodium adsorption ratios (SAR) on cotton growth and yield can vary under the same degree of mineralization in irrigation water. Therefore, to further explore the effects of irrigation water mineralization and SAR on cotton, we established three mineralization treatments at 3 g·L-1(T3), 5 g·L-1(T5), and 7 g·L-1(T7). Additionally, we designed three SAR treatments at 10 (mmol·L)1/2(S10), 15 (mmol·L)1/2(S15), and 20 (mmol·L)1/2(S20). Local freshwater irrigation served as a control (CK). In total, 10 treatments were conducted in this experiment to examine the combined effects of irrigation water mineralization and SAR costress on soil salinity, cotton growth, plant ion accumulation, yield, and water use efficiency. The results indicated that soil salinity increased with higher irrigation water mineralization or SAR, initially rising before decreasing with increasing soil depth. Plant Na+ content increased with increasing irrigation water mineralization or SAR, with the interaction effect between these factors being highly significant. Conversely, plant K+, K+/Na+, and N content decreased as irrigation water mineralization or SAR increased. Additionally, plant height, stem thickness, leaf area index, and dry matter mass all showed a significant decreasing trend with increased irrigation water mineralization and SAR, with significant inhibition of dry matter accumulation observed. Irrigation water mineralization and SAR significantly affected the number of bolls per plant, boll weight, seed cotton yield, and water consumption (ET). Moreover, irrigation water SAR significantly affected water use efficiency (WUE). Compared to the CK treatment, yield and WUE increased by 3.27% and 1.09% in T3S10, 2.54% and 0.47% in T5S10, and 1.18% in T3S15, respectively. This increase indicated that moderately reducing the irrigation water SAR can help mitigate yield reduction in cotton due to increased mineralization. Different levels of mineralization and SAR in irrigation water increased the Na+ content in cotton plants while reduced K+ and N nutrient uptake, and increased the K+/Na+ ratio. Consequently, cotton plant height, stem thickness, leaf area, and dry matter accumulation gradually decreased as irrigation water mineralization or SAR increased. The number of bolls per plant and boll weight increased in the T3S10, T3S15, and T5S10 treatments compared to the CK treatment. In conclusion, using brackish water with an irrigation water mineralization of 3 g·L-1 and SAR below 15 (mmol·L-1)1/2, or an irrigation water mineralization of 5 g·L-1 with SAR below 10 (mmol·L-1)1/2, can ensure cotton yield. These findings provide a theoretical basis and reference for the efficient use of brackish water in Xinjiang and other extreme arid regions.
