Optimizing alternate brackish and freshwater drip irrigation with film mulching for cotton production in Southern Xinjiang

【Objective】 Southern Xinjiang has limited freshwater but relatively abundant saline groundwater. To optimize the use of these water resources, we investigate the effect of alternate brackish and freshwater drip irrigation with film mulching on soil water and salt movement, as well as seed yield of cotton. 【Method】 The experiment was conducted at the Xinjiang Alar Modern Agricultural Comprehensive Experimental Station. It compared nine combinations of brackish and freshwater drip irrigation. In each treatment, we measured the spatiotemporal changes in soil water and salt, as well as growth, and seed yield of the cotton. 【Result】 During the growth period of the cotton, soil water and salt increased with increased use of brackish water. When the amount of brackish water used for irrigation was the same, continuous use of freshwater irrigation in the early growth stage of the cotton was effective to reduce salt content in the root zone. Increasing the use of brackish water in irrigation inhibited crop growth. Moderate use of brackish water in the flowering and boll development stages can promote reproductive growth, however, excessive use would significantly reduce the weight of single bolls. Appropriately alternating brackish and freshwater irrigation not only ensures vegetative growth in the early stages but also promotes reproductive growth during flowering and boll development stage of the cotton. 【Conclusion】 In Southern Xinjiang, alternating brackish and freshwater in drip irrigation with film mulching should keep the brackish water ratio below a specific threshold. Its usage should be minimized during the seedling, budding, and early flowering stages, but can be increased during the flowering and boll development stages. In this experiment, the optimal irrigation sequence was freshwater-freshwater-brackish water.