Effects of soil water–heat–salt synergy on cotton growth under drip irrigation in northern Xinjiang: Precision control based on irrigation upper and lower limits

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Context The arid regions of northern Xinjiang face limited water resources and severe soil salinization. Therefore, optimizing irrigation systems to cumulatively regulate soil moisture, temperature, and salinity is essential to advancing cotton growth, improving water–use efficiency, and fostering sustainable development within the regional cotton industry. Accordingly, the current study evaluated the impact of soil water, temperature, and salinity levels on cotton growth and yield. Methods Field trials of drip–irrigated cotton were conducted over two years in the field. Irrigation was controlled within preset upper and lower limits to clarify how various factors interact in crop development. Results High–frequency, low–volume drip irrigation consistently enhanced soil moisture, promoted thermal accumulation, and substantially increased the soil salinity reduction rate ( SR ). Under controlled irrigation limits, 0∼80 cm effective accumulated soil water storage ( SW ) and 0∼80 cm soil accumulated temperature ( SEAT ) increased by 11.86%–40.09% and 1.32%–15.63%, respectively, compared to conventional drip–irrigation treatment (CK). The highest 0∼80 cm SR was achieved when irrigation limits during squaring period, flowering and boll–setting period were maintained at 70–85% and 70–90% field capacity (FC), respectively (F2B3), resulting in a 79.21% increase over CK. The irrigation system ( I m and I t ) exerts a significant positive driving effect on the 0∼80 cm soil environment ( SW, SEAT and SR ) (β = 0.756, p < 0.05), while the soil environment in turn exerts a significant positive influence on Y (β = 0.834, p < 0.05), WUE (β = 0.523, p < 0.05), and crop growth ( H m , D m , G m , and S m ) (β = 0.721). The irrigation system's direct effects on Y , WUE , and crop growth were not significant, indicating that it primarily enhances production efficiency indirectly by improving the soil environment. The model exhibited good overall fit (GOF = 0.43), explaining 57%, 54%, 58%, and 46% of the variance in soil environment, crop growth, Y , and WUE , respectively. It effectively captured the regulatory mechanisms of the irrigation-soil-crop system on cotton production efficiency. The F2B3 treatment produced the highest lint cotton yield and water use efficiency, with respective increases of 29.46% and 52.50% compared to CK. Conclusions Identify a plan that achieves a more balanced overall performance in terms of cotton seed yield–water use efficiency–soil health, it is advised that upper and lower irrigation thresholds for cotton cultivated under plastic–mulched drip irrigation in northern Xinjiang be set at 70–85%FC and 70–90%FC during squaring period, flowering and boll–setting period.

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