Irrigation with ionized brackish water affects cotton yield and water use efficiency

Irrigation agriculture, which is commonly applied in the arid area in Northwest China, faces multiple threats, including drought, shortage of freshwater supply to irrigation districts and soil salination. Reducing salinity damage to plant growth and, improving irrigation water productivity with ionized brackish water are crucial for sustaining the agricultural production in the region. In the current study, we determined the responses of cotton (Gossypium hirsutum L.) growth, yield and, water productivity for several irrigation amounts and ionized treatments at southern Xinjiang, China. We applied five drip irrigation treatments: (W1, 262.5 mm; W2, 337.5 mm; W3, 412.5 mm; W4, 487.5 mm; and W5, 562.5 mm) of non-ionized and ionized brackish water, resulting in total of 10 treatments, (NIW1, NIW2, NIW3, NIW4, NIW5, IW1, IW2, IW3, IW4 and IW5). The experimental design incorporated 10 irrigation treatments in a randomized block design with four replicates. Results demonstrated the improvements in plant height, leaf area index, shoot dry matter, boll number per plant and chlorophyll content resulting from the ionized treatment. Moreover, the ionized treatment effectively reduced salt accumulation amount from late seedling stage to harvest by 12.8%-65%, especially in 562.5 mm of ionized brackish water treatment. The maximum cotton yield was obtained in 487.5 mm of ionized brackish water treatment, with increases of an average of 19% compared to 487.5 mm of non-ionized brackish water treatment. Water use efficiency increased significantly under the ionized brackish water treatments. A quadratic relationship was observed between irrigation amount and the cotton yield. Based on the soil salt, cotton yield and irrigation water use efficiency, the irrigation amount was optimized at 487.5 mm for ionized brackish water-drip irrigation plastic film mulching systems. This study provides valuable guidance on the use of brackish water irrigation to improve water productivity while maintaining an acceptable cotton yield in the arid area.