The assessment of soil health relies on key parameters such as soil aggregates and organic matter content. Therefore, examining the impact of irrigation water ion composition and variations in salinity on soil aggregates and organic matter is imperative, which is key to developing a theoretical basis for the sustainable utilization of saline water resources, particularly in extremely arid regions. This experiment was conducted to investigate the impact of different irrigation water salinity treatments (T3: 3 g/L, T5: 5 g/L, and T7: 7 g/L) on the root zone soil of cotton fields. Each salinity treatment included three variations of the sodium adsorption ratio (SAR) at S10: 10 (mmol/L)^1/2, S15: 15 (mmol/L)^1/2, and S20: 20 (mmol/L)^1/2. Local freshwater irrigation served as the control, resulting in a total of 10 treatments. Our findings show that the soil Ca²⁺ and Mg²⁺ content increased with higher irrigation water salinity but decreased with increasing irrigation water SAR. The relative macroaggregate stability and the content of water-stable macroaggregates and soil organic matter (SOM) decreased as the irrigation water salinity and SAR increased. In comparison to T3S20, T5S10 did not improve the soil Na⁺ content but significantly increased the soil Ca²⁺ content by 147.76%, while the water-stable aggregate and SOM saw a notable increase of 7.66% and 9.86%, respectively. Reducing the SAR in brackish water lessens its negative impact on soil aggregates in cotton fields. This is primarily because Ca²⁺ counteracts the dispersive effect of high Na⁺ concentrations and promotes aggregate formation. Irrigation water with a salinity of 3 g/L and an SAR of 10 (mmol/L)^1/2 positively affected the stabilization of soil aggregates and organic matter.

The yield, quality, and water–fertilizer use efficiency of crops are important parameters for assessing rational water and fertilizer management. For an optimal water and fertilizer system with respect to the nutrient solution irrigation of greenhouse tomatoes using cultivation substrates, a two-year greenhouse cultivation experiment was conducted from 2022 to 2023. Three drip fertigation treatments (T1, T2, and T3) were implemented in the experiment, where nutrient solutions were supplied when the substrate’s water content reached 60%, 70%, and 80%. The frequency of nutrient solution applications is based on weighing coconut coir strips in the morning and evening at 7:00 to determine the daily water consumption of plants. Nutrient solutions were supplied when the substrate’s water content reached the lower limit, and the upper limit for nutrient supply was set at 100% of the substrate water content. The nutrient solution application was carried out multiple times throughout the day, avoiding the midday heat. The nutrient solution formula used was the soilless tomato cultivation formula from South China Agricultural University. The results show that plant height and the leaf area index rapidly increased in the early and middle stages, and later growth tended to stabilize; the daily transpiration of tomatoes increased with an increase in nutrient solution supply, and it was the greatest in the T3 treatment. Between the amount of nutrient solution application and the number of years, the yield increased with the increase of the amount of nutrient solution, showing T3 > T2 > T1. Although the average yield of the T2 treatment was slightly lower than that of the T3 treatment by 3.65%, the average irrigation water use efficiency, water use efficiency, and partial fertilizer productivity of the T2 treatment were significantly higher than those of the T3 treatment by 29.10%, 19.99%, and 28.89%, respectively (p < 0.05). Additionally, soluble solid, vitamin C, and soluble sugar contents and the sugar–acid ratio of tomatoes in the T2 treatment were greater than those in the other two treatments (p < 0.05). Using the TOPSIS (Technique for Order Preference by Similarity to an Ideal Solution) method, it was concluded that the nutrient solution application rate of 70% can significantly increase water and fertilizer use efficiency and markedly improve the nutritional and flavor quality of the fruit without a significant reduction in yield. This finding provides significant guidance for the high-yield, high-quality, and efficient production of coconut coir-based cultivated tomatoes in greenhouses.

To address the scientific challenges of low water–fertilizer use efficiency and the difficulty in achieving the synergistic improvement of the yield and quality in solar greenhouse cucumber production on the North China Plain, this study investigated the effects of varying water and nitrogen supplies on cucumber growth, yields, water–nitrogen use efficiency, and quality. The aim was to establish optimized water and nitrogen management strategies for high-yield, high-quality, and resource-efficient cultivation. A two-factor completely randomized design was implemented, with three irrigation levels (W1: $1.0E_{p-20}$, W2: $0.75E_{p-20}$, and W3: $0.5E_{p-20}$) based on cumulative pan evaporation and four nitrogen application amounts (N1: 432 kg·ha⁻¹, N2: 360 kg·ha⁻¹, N3: 288 kg·ha⁻¹, N4: 216 kg·ha⁻¹). Cucumber growth indicators were observed during the growing season, and the water and nitrogen application rates were scientifically optimized. The results showed that a full water and nitrogen supply enhanced the leaf area index, dry weight accumulation, and yield. Moderate water and nitrogen savings had a minimal impact on plant growth and production while significantly improving the water and fertilizer use efficiency. Using principal component analysis to comprehensively evaluate the cucumber quality, it was found that the irrigation amount had a significant impact on quality, with the quality improving as the irrigation amount decreased. By employing a regression formula and spatial analysis methods, this study optimized the water and nitrogen application rates with the goals of maximizing the cucumber yield, water–nitrogen efficiency, and quality. For spring cucumbers, the recommended combination is an irrigation amount of 225~240 mm and a nitrogen application amount of 350~380 kg·ha⁻¹. For autumn cucumbers, the recommended combination is an irrigation amount of 105~120 mm and a nitrogen application amount of 375~400 kg·ha⁻¹. This research provides theoretical and technical support for high-yield, high-quality, and efficient irrigation and nitrogen management in solar greenhouses in the North China Plain.

Reasonable development and utilization of brackish-water resources can alleviate the pressure of freshwater scarcity in dryland areas and safeguard crop growth, but there are significant differences in brackish-water ions in different regions. Thus, exploring the mechanism of brackish-water irrigation considering brackish-water ionic differences on the growth and development of saline and alkaline dryland crops has an important production guidance value. In this study, the ionic differences in irrigated brackish water were characterized by sodium adsorption ratio using under-membrane drip-irrigated cotton as the research object, and three levels of mineralized irrigation water were designed, which were 3 g·L⁻¹ (T3), 5 g·L⁻¹ (T5), and 7 g·L⁻¹ (T7), respectively. Three different levels of sodium adsorption ratio (SAR) were set under each level of mineralization, which were 10 (mmol·L⁻¹)¹/² (S10), 15 (mmol·L⁻¹)¹/² (S15), and 20 (mmol·L⁻¹)¹/² (S20). The local freshwater irrigation was used as a control treatment. The results showed that brackish-water irrigation increased soil salt accumulation and soil water content, induced oxidative damage and disruption of ionic homeostasis in the cells, and decreased leaf photosynthetic rate. Brackish-water irrigation also significantly reduced dry matter mass by 11.04–50.12%. Reduced irrigation water SAR (S10 and S15) enhanced antioxidant enzyme activities such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), and reduced malondialdehyde (MDA) content by 14.29% and 9.09%, respectively, compared with high irrigation water SAR (S20). Leaf K⁺ uptake was increased by 5.29% and 1.57% in S10 and S15, respectively, compared with S20, while Na⁺ uptake was significantly suppressed. The K⁺/Na⁺ ratio increased by 45.07%, which resulted in improved leaf photosynthetic efficiency by 25.25% and 11.91%, and significantly enhanced dry matter accumulation by 24.81% and 11.20%, respectively. In addition, compared with T3S20, the T5S10 treatment reduced the irrigation water SAR. It contributed to a significant increase in SOD, POD, and CAT activities by 30.42%, 60.70%, and 99.20%, respectively, and in plant K⁺ content and K⁺/Na⁺ by 2.48% and 38.85%, respectively, although the irrigation water mineralization increased by 66.67%. Reducing SAR could enhance photosynthesis and dry matter accumulation through the dual regulation of “antioxidant damage + ion homeostasis” in salt-stressed cotton, laying a foundation for the realization of stable and high yields of cotton under brackish-water irrigation, and providing a new perspective for the management of brackish-water resources and the sustainable development of agriculture in Xinjiang and other arid regions.

Soil salinity and water deficit are important challenges for sustainable agricultural development in arid and semi-arid regions. While soil salinity and water deficits may result in lower crop yields, they may improve crop quality. The quantitative relationship between water–salt stress, crop yield, and quality is key to achieving stable yield and enhanced quality through the coordinated regulation of soil water and salt. The interaction between soil salinity and deficit irrigation on tomato quality needs to be further understood, and the model simulating the response of tomato quality to deficit irrigation under simulated soil salinity needs to be further optimized. In this study, a two-year experiment was conducted in northwest China consisting of combinations of three soil salinity levels (0 g, 3 g, and 5 g mixed salt added to 1000 g air-dried soil, respectively) and four water regimes relative to the field capacity (θ_f) (W0, W1, W2, and W3 refer to 95% θ_f, 80% θ_f, 70% θ_f, and 60% θ_f as the upper limit of soil water content, respectively). The responses of plant stem water potential (φ), fruit osmotic potential (φ_π), fruit Na⁺ content, fruit fresh weight, fruit water content, total soluble solids (TSS), lycopene (Ly), soluble sugars content (SSC), and color index (CI) to the degree of water deficit and the stage of water deficit were analyzed under soil salinity. The results show that both soil salinity and water deficit significantly reduced φ, but there is no significant interaction. TSS, SSC, and CI are all significantly affected by soil salinity, degree of water deficit, and stage of water deficit, and there is a significant interaction between the degree of water deficit and soil salinity. Fruit fresh weight, TSS, Ly, SSC, and CI are all strongly correlated with φ, and the straight lines of regression of each index with φ are significantly affected by soil salinity content. Soil salinity significantly increased the Na⁺ content in the fruit, and water deficit significantly enhanced the effect of soil salinity on the Na⁺ content of tomato fruit. A functional model to simulate fruit quality was developed based on the response of fruit quality parameters to φ and the effect of fruit Na⁺ accumulation under the compound effect of soil salinity and water deficit. The validation results of the model show that this function model effectively simulates tomato fruit quality under the combined effects of soil salinity and water deficit, providing a theoretical basis for soil water–salt management in arid and semi-arid regions.

Mulching and irrigation are key practices for improving cotton yield and soil conditions, especially in Xinjiang, China. This study investigated the combined effects of mulching width and irrigation depth on cotton growth and rhizosphere microorganisms. Two mulching widths—conventional (M1) and ultra-wide (M2)—and three irrigation depths, 0.8 ETc (W1), 1.0 ETc (W2), and 1.2 ETc (W3), were tested. The impacts on cotton growth, soil environment, and rhizosphere microbial communities were analyzed. Results showed that under the same irrigation depth, M2 significantly increased soil moisture and reduced salt accumulation. Soil temperature under M2 was higher than M1, with increases of 0.55 °C and 1.65 °C during the budding and flowering–boll stages. M2 also increased root length (3.52–10.72%) and root surface area (5.8–7.51%). The beneficial fungus Cladosporium was enriched, while the pathogen Fusarium was suppressed under M2. With the same mulching width, increasing irrigation improved soil moisture, reduced electrical conductivity, and decreased soil temperature. Root diameter and volume increased by 7.67–47% and 9.43–10.36%, respectively. Mulching width and irrigation depth significantly affected bacterial α-diversity. M2W3 showed the highest microbial richness and functional diversity. This study offers guidance for efficient cotton cultivation in southern Xinjiang.