Regulation of Soil Water–Salt Dynamics and Cotton Growth in Saline Cotton Fields Through Optimization of Drip Emitter Parameters and Irrigation Quotas

Soil salinization constrains cotton production in arid regions, making the optimization of water and salt regulation in drip irrigation systems crucial for enhancing water use efficiency and yield in saline cotton fields. This study aimed to evaluate the synergistic effects of emitter parameters and irrigation quotas on water-salt regulation and cotton growth in a salinized field. Treatments included conventional and leaching irrigation quotas, combined with emitter flow rates of 1.4–3.0 L/h and emitter spacings of 20–30 cm. Soil water-salt dynamics, cotton growth, and yield responses were monitored. The results indicated that the irrigation quota was the dominant factor regulating root-zone water retention and salt leaching, with leaching quotas significantly enhancing soil moisture and desalination compared to conventional quotas. Emitter parameters significantly modulated water and salt distribution. A moderate flow rate of 2.4 L/h combined with a 30 cm spacing created more uniform soil moisture distribution and more efficient salt leaching within the root zone. Cotton growth and yield responded markedly to this water-salt regulation pattern. The combination of a 2.4 L/h flow rate, 30 cm spacing, and the leaching quota achieved the highest seed cotton yield of 6343.12 kg/hm2. However, increasing the irrigation quota reduced irrigation water productivity from 1.26 kg/m³ to 0.97 kg/m3. An optimization model for yield and salt leaching efficiency, developed based on experimental data, identified an optimal parameter combination for balancing high yield and efficient salt control: emitter flow rate of 2.1–2.4 L/h, spacing of 30 cm, and irrigation quota of 60–66 mm. This combination is projected to achieve a yield of 6356.68 kg/hm2 and a salt leaching efficiency of 6.48%. This study provides a quantitative basis for optimizing drip irrigation system parameters and the management of water and salt in saline cotton fields in the arid region of Xinjiang.