Water scarcity constrains the sustainable development of Chinese agriculture, and deficit irrigation as a new irrigation technology can effectively alleviate the problems of water scarcity and water use inefficiency in agriculture. In this study, the drip irrigation cotton field under film in Xinjiang was taken as the research object. Meta-analysis and machine learning were used to quantitatively analyze the effects of different farm management practices, climate, and soil conditions on cotton yield and water use efficiency under deficit irrigation, to investigate the importance of the effects of different factors on cotton yield and water use efficiency, and to formulate appropriate optimization strategies. The results showed that deficit irrigation significantly increased cotton water use efficiency (7.39%) but decreased cotton yield (−15.00%) compared with full irrigation. All three deficit irrigation levels (80~100% FI, 60~80% FI, and 40~60% FI; FI: full irrigation) showed a significant decrease in cotton yield and a significant increase in water use efficiency. Under deficit irrigation, cotton yield reduction was the smallest and cotton water use efficiency increased the most when planted with one film, two tubes, a six-row cropping pattern, an irrigation frequency ≥10 times, a nitrogen application of 300~400 kg·ha⁻¹, and a crop density ≥240,000 per hectare, and planted with the Xinluzhong series of cotton varieties; deficit irrigation in areas with average annual temperature >10 °C, annual evapotranspiration >2000 mm, annual precipitation <60 mm, and with loam, sandy soil had the least inhibition of cotton yield and the greatest increase in cotton water use efficiency. The results of the random forest showed that the irrigation amount and nitrogen application had the greatest influence on cotton yield and water use efficiency. Rational irrigation based on optimal management practices under conditions of irrigation not less than 90% FI is expected to achieve a win–win situation for both cotton yield and water use efficiency. The above results can provide the best strategy for deficit irrigation and efficient water use in drip irrigation cotton under film in arid areas.

As one global issue, soil salinization has caused soil degradation, thus affecting the sustainable development of irrigated agriculture. A two-year study was conducted in 2018 and 2019 to identify the effects of subsurface drainage spacing on soil salinity and groundwater level, the latter of which is in a high-water table in drip irrigation cotton fields in the Tarim Basin oasis in southern Xinjiang, China. Three subsurface drainage treatments, with a drain spacing of 10 m (W10), 20 m (W20), and 30 m (W30), respectively, and a drainage-absent treatment (CK), are tested. With CK, soil salinity in the 0–60 cm layer was accumulated within a year. In contrast, the subsurface drainage reduced the soil salinity at a leaching rate of 10–25%. When decreasing the drain spacing, it was found that the soil desalination rate increased significantly (p < 0.05) with good repeatability. Experimental results showed that the fitting equation of the soil salinity leaching curve could accurately describe the soil salinity leaching pattern of drip irrigation, and thus could be further used to inversely determine the theoretical drip irrigation leaching quota for those soils with different salinity degrees. As such, subsurface drainage could effectively control the groundwater table. Compared with CK, subsurface drainage deepened the groundwater table and mitigated the fluctuation of the groundwater level. These effects were strengthened by reducing the drain spacing. Correspondingly, the influence of the fluctuation of the groundwater table was reduced.

The effective exploration and utilization of brackish water resources are crucial to alleviating the scarcity of freshwater in arid regions. This study focused on protected tomato plants and set up four irrigation salinity levels: T1 (2 g·L⁻¹), T2 (4 g·L⁻¹), T3 (6 g·L⁻¹), and T4 (8 g·L⁻¹), with freshwater irrigation as a control (CK). The aim was to investigate the effects of continuous brackish water irrigation on soil water-salt transport and tomato yield. The outcomes highlighted that the moisture content in different layers of soil exhibited a “high in the middle, low at both ends” pattern, with the primary accumulation of soil moisture occurring at the 40 cm depth. The range and moisture content of the soil wetted zone increased with elevated salinity levels. Under continuous brackish water irrigation, the range of the soil wetted zone expanded further for the autumn crops, and the moisture content significantly increased compared to the spring crops. The concentration of soil salt gradually decreased with increasing soil depth, exhibiting greater levels in the 0–20 cm layer compared to the 40–80 cm layer. The average salt concentration in the soil at the end of the growth period was significantly higher than before transplantation, and this phenomenon became more pronounced with increasing salinity levels. Initial irrigation with brackish water with a salinity level of 2–4 g·L⁻¹ promoted the growth of the tomatoes planted in the spring and the plant height and stem diameter reached the peak values of 1.68 m and 1.08 mm for the T2 treatment, respectively, which were 7.1% and 9.2% higher than that of the CK treatment, ensuring efficient yield and water usage. However, continuous irrigation with brackish water with a salinity level of 2–4 g·L⁻¹ inhibited the growth and yield of the tomatoes planted in autumn, while the T1 and T2 treatments only yielded 24,427.42 and 16,774.86 kg·hm⁻², respectively, showing a decline of 32.2% and 46.1% compared to the yields of the spring season. Considering the soil water-salt and yield indicators, under the conditions of non-continuous brackish water irrigation, using water with a salinity level of 2–4 g·L⁻¹ is recommended for drip irrigation of protected tomatoes.

Efficient utilization of saline water and yellow sand resources can enhance water and soil resource management while boosting crop yields in Xinjiang. This study conducted a two-season field experiment in Alar City, Xinjiang, from March to July 2023 and August 2023 to January 2024. The objective was to examine the effects of different irrigation water salinities (2, 3, 4, 5, and 6 g·L⁻¹) on the physiology, growth, and yield of sand-cultured tomatoes grown in yellow sand slag. Groundwater irrigation with salinity levels of 0.8–1 g·L⁻¹ was used as the control (CK). The results showed that the salinity of the substrate gradually increased with the salinity of irrigation water in each treatment. The salt accumulation increased by 59.5%, 82.5%, and 99.5% at the end of the experiment for T3 (4 g·L⁻¹), T4 (5 g·L⁻¹), and T5 (6 g·L⁻¹), respectively, compared to CK. As the salinity of irrigation water increased, plant height, stem thickness, chlorophyll content, net photosynthesis rate, stomatal conductance, transpiration rate, and total yield of tomato showed an increasing and then decreasing trend, in which the total tomato yield of the T2 (3 g·L⁻¹) treatment was significantly increased by 35.2% compared with that of CK between the two seasons. In contrast, as the salinity of irrigation water increased, the inter-cellular CO₂ concentration of tomato leaves showed a decreasing and then increasing trend, with the T2 treatment having the lowest inter-cellular CO₂ concentration. Pathway analysis revealed that appropriate salinity levels increased tomato yield by regulating inter-cellular CO₂ concentration. Based on these findings, a 3 g·L⁻¹ salinity level is recommended for irrigating sand-cultured tomatoes to maximize yellow sand resource use, address freshwater shortages, and optimize water and soil management in the Xinjiang region.