Effects of brackish water irrigation on the physiological characteristics, yield and quality of mulched drip irrigation cotton under different soil textures

Using brackish water for irrigation in arid and semi-arid areas can alleviate the supply-demand contradiction of freshwater resources. However, the correlation between its irrigation effect and soil texture remains to be studied. This study investigated the effects of irrigation mineralization on the growth and development of drip-irrigated cotton with different soil textures and the yield and fiber quality of seed cotton. In 2022, a barrel planting experiment was conducted to study two common cotton field soil textures (sandy loam soil T1 and sandy soil T2) and four irrigation mineralization degrees (0.85 (S0), 2.00 (S1), 5.00 (S2), and 8.00 g/L (S3)) in the Manas River Basin. Under different treatments, eight experimental treatments were used to study cotton photosynthetic indicators, plant height, stem diameter, yield, and quality. The results showed that as the mineralization degree of irrigation increased, the plant height, stem diameter, net photosynthetic rate, transpiration rate, single boll weight, number of bolls per plant, yield, irrigation water use efficiency, and fracture ratio intensity of cotton seedlings in sandy soil showed a decreasing trend after the seedling stage. The transpiration rate of S3 treatment decreased by 10.61% compared to S0 during the bud stage. Under sandy loam conditions, all indicators showed an increasing and decreasing trend. The net photosynthetic rate of S1 treatment increased by 8.40% compared to S0. As irrigation's mineralization degree increases, underground cotton's maximum fluorescence in two soil types decreases, while nonphotochemical quenching shows an increasing trend. It can be concluded through regression analysis that there is a negative correlation between cotton yield and irrigation mineralization in sandy soil cotton fields. However, irrigation water less than 3.69 g/L in sandy loam cotton fields will not reduce cotton yield. Using path analysis, it can be concluded that cotton stem diameter and transpiration rate are the main factors affecting yield under sandy loam conditions. Plant height is the main factor affecting the micronaire value. Under sandy soil conditions, the nonphotochemical quenching coefficient and transpiration rate are the main factors affecting yield. In contrast, plant height and transpiration rate are the main factors affecting micronaire value. This study can provide a theoretical basis and technical support for the rational utilization of brackish water resources in cotton fields with different soil types in the Manas River Basin.