This research provides a comprehensive analysis of the spatiotemporal evolution of the regional cropping structure and its influencing factors. Using Landsat satellite images, field surveys, and yearbook data, we developed a planting structure extraction model employing the classification regression tree algorithm to obtain data on the major crop cultivation and structural characteristics of Alar reclamation from 1990 to 2023. A dynamic model and transfer matrix were used to analyze temporal changes, and a centroid migration model was used to study spatial changes in the cropping structure. Nonparametric mutation tests and through-traffic coefficient analysis were utilized to quantify the main driving factors influencing the cropping structure. During the period of 1990–2023, the cotton area in the Alar reclamation region expanded by 722.08 km², while the jujube exhibited an initial increase followed by a decrease in the same period. The primary reasons are linked to the cost of purchase, agricultural mechanization, and crop compatibility. In the Alar reclamation area, cotton, chili, and jujube are the primary cultivated crops. Cotton is mainly grown on the southern side of the Tarim River, while chili cultivation is concentrated on the northern bank of the river. Over the years, there has been a noticeable spatial complementarity in the distribution and density of rice and cotton crops in this region. In the Alar reclamation, the main factors influencing the change in cultivated land area are cotton price, agricultural machinery gross power, and population. Consequently, implementing measures such as providing planting subsidies and other policy incentives to enhance planting income can effectively stimulate farmers’ willingness to engage in planting activities.

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.

In global drought-prone cotton-growing (Gossypium hirsutum L.) areas, saline water irrigation has become a key strategy to alleviate the shortage of freshwater resources. Against this backdrop, the synergistic effect of mineralization degree (MD) and sodium adsorption ratio (SAR) on the rhizosphere microecological regulation mechanism remains unclear. To address this issue, this study constructed an experimental framework of the interaction between MD and SAR, aiming to explore their effects on the bacterial community structure in the rhizosphere of cotton and the soil environment. The soil type in the study area is saline–sodic sandy loam. In the experimental design, three MD levels (3 g/L, 5 g/L, 7 g/L) were set, and under each mineralization condition, three SAR levels (10 (mmol/L)^1/2, 15 (mmol/L)^1/2, 20 (mmol/L)^1/2) were arranged. In addition, local freshwater irrigation was used as the control group (CG), resulting in a total of 10 treatment schemes. The aim of this study was to investigate the effects of varying levels of irrigation water MD and SAR on the structure of bacterial communities in cotton rhizosphere soil and the soil environment. The results indicated that saline water irrigation could enhance the diversity and richness of the bacterial community in the rhizosphere soil of cotton and alter its community structure. Under treatment with the MD of 3 g/L and the SAR of 10 (mmol/L)^1/2, the diversity and richness of the bacterial community in the cotton rhizosphere reached their peak levels. Compared with the CG, the Chao1 index significantly increased by 260 units, while the Shannon index increased by 0.464. When the MD does not exceed 5 g/L, reducing SAR can enhance the diversity and network stability of the rhizosphere bacterial community, thereby synergistically promoting the accumulation of soil nutrients. The key soil environmental factors driving changes in the rhizosphere bacterial community structure mainly include soil moisture content, total nitrogen, nitrate nitrogen, and total organic carbon. The concentrations of total nitrogen, nitrate nitrogen, available phosphorus, and available potassium significantly increased by 19.66%, 26.10%, 89.41%, and 49.76% respectively (p < 0.05). This study provides a theoretical basis for sustainable irrigation and microbial regulation strategies in saline–alkali cotton fields at the theoretical level, and offers a new perspective for revealing the mutual feedback mechanism between bacterial community assembly and soil environment under saline conditions. From a practical perspective, this research offers valuable hands-on experience for optimizing agricultural ecological management in saline–alkali sandy loam soils, thereby contributing to the sustainable development of agriculture on such lands.

Regulated deficit irrigation is a vital method for developing water-saving agriculture. The degree of and the period of water deficit are two key factors determining the effectiveness of regulated deficit irrigation. In this study, winter wheat was used as the experimental material, and water deficit was imposed by reducing the irrigation lower limit. Three water deficit treatments were established, with irrigation lower limits set at 65%, 55%, and 45% of field capacity, respectively. There were three stages of water deficit: the jointing stage, the heading-anthesis stage, and the ripening stage; full irrigation (with a minimum irrigation level of 75% field capacity) served as the control. The physiological and growth indicators were measured, including plant water status, osmotic regulation, antioxidant activity, leaf gas exchange and yield. The variation patterns of physiological indicators during the irrigation cycle under reduced irrigation lower limits at different growth stages were explored. The synergistic response relationships among physiological indicators were analyzed; the physiological mechanism by which the degree and stage of water deficit jointly influence winter wheat yield was elucidated. The results indicate that lowering the lower limit of irrigation reduces net photosynthesis prior to irrigation. When the lower irrigation threshold exceeds 55%, chlorophyll content remains largely unaffected. However, increased stomatal conductance following irrigation results in higher net photosynthesis under the low irrigation threshold treatment compared to the control. When the irrigation lower limit is below 55%, chlorophyll content decreases significantly, resulting in net photosynthesis remaining markedly lower than the control even after irrigation. During the jointing stage and heading-anthesis stage, plants exhibit weaker osmotic regulation and antioxidant capacity, and the chlorophyll content is greatly affected by water deficit, resulting in reduced net photosynthesis before and after irrigation, leading to a greater decrease in winter wheat yield. The results on the physiological and biochemical characters (excluding gas exchange parameters) are limited to one year. The research findings provide the theoretical reference for regulated deficit irrigation of winter wheat.

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.