The response of alfalfa to water and salinity stress differs during the whole growth period, and water stress has the most severe effects on the yield of alfalfa at the branching stage. However, the presence of soil salt can also enhance its drought resistance and alleviate the impact of water stress on yield. Thus, information on the responses of aboveground biomass, water-use efficiency and osmolytes to water and salinity stress at the branching stages of alfalfa development is urgently required. A pot experiment that combined three irrigation levels of 55–70% (W1), 70–85% (W2) and 85–100% (W3) of field capacity (FC) and four salinity levels was conducted in Dengkou County, Inner Mongolia, China, in 2018 and 2019. The percentage of mixed salt (NaCl:Na₂SO₄ = 1:1 [w/w]) added for the salinity treatments was 0, 2, 4 and 6% of the soil dry weight and was designated as S0–S3, respectively. The water consumption, biomass, osmolytes, such as proline and Na⁺, and the activities of antioxidant enzymes, such as superoxide dismutase (SOD) and peroxidase (POD), of alfalfa were measured during its early flowering stage. In general, the plant height, aboveground biomass, root biomass and water consumption of alfalfa increased with the decrease in soil salinity and increase in the amount of irrigation applied. When the salt >3 g kg⁻¹, alfalfa could improve its stress resistance by increasing the contents of proline and Na⁺ and the activity of POD and decreasing the activity of SOD, but the aboveground biomass and water consumption decreased. However, alfalfa has a certain cross adaptation ability under water and salt stress at the branching stage, particularly when salt is less than 3 g kg⁻¹. Compared with single water stress, adding an appropriate amount of salt (≤3 g kg⁻¹) increased the contents of proline and Na⁺ and the activities of SOD and POD, which led to water consumption and aboveground biomass of alfalfa increases of 11.93% and 17.51%, respectively. In conclusion, the alfalfa was tolerant to moderate (3 g kg⁻¹) salt stress. The alfalfa with higher proline, SOD and POD activity and Na⁺ was better able to yield well under salt stress. Meanwhile, combined with moderate irrigation (70–85% FC), the productivity of alfalfa was improved better. The results can provide a theoretical basis for the utilization of alfalfa in salinized land.

Microorganisms play a crucial role in biogeochemical cycling within wetland ecosystems. Soil-environment-mediated seasonal changes in microbial structure require further investigation. However, the factors driving seasonal variations in the microbial abundance and diversity in the Daihai wetlands remain unclear. This study employed high-throughput sequencing technology to examine the bacterial community structure and diversity in the lakeshore zone of Daihai across different seasons and to explore the seasonal variations in the bacterial community structure and the influence of driving factors. The results indicated that Pseudomonadota and Bacteroidota dominate in spring and Pseudomonadota abundance further increases in summer, while organic-matter-decomposing microorganisms (e.g., Actinobacteriota and Bacteroidota) dominate in autumn. Microbial diversity indices indicated a significantly greater diversity in spring than in summer and autumn (p < 0.05). Changes in environmental variables were strongly associated with bacterial community changes, with variations in total nitrogen, ammonium nitrogen, and soil moisture content being identified as potential key factors influencing seasonal bacterial diversity trends. Furthermore, bacterial community assembly in spring is driven by both stochastic processes and environmental selection, suggesting that abundant nutrients and organic matter promote bacterial diversity. The findings of this study provide a theoretical basis for wetland ecosystem restoration and conservation.

Soil salinization and freshwater scarcity are two of the most pressing challenges limiting sustainable agriculture in arid and semi-arid regions worldwide. Magnetized irrigation has been proposed as a physical water treatment that introduces no chemical additives and may improve water infiltration and mitigate secondary salinization; however, its effectiveness under contrasting irrigation water sources remains poorly understood, particularly in undisturbed saline–alkali soils. This study investigated the effects of magnetized irrigation water from two sources—Yellow River water (HW) and subsurface drainage water (DW)—on soil water infiltration and water–salt transport in the Hetao Irrigation District, Inner Mongolia. Undisturbed soil columns were irrigated under three magnetic field intensities: 0, 3500, and 5000 Gauss (Gs). Cumulative infiltration, infiltration rate, wetting front advancement, soil moisture, salt storage, and ion redistribution were analyzed. Magnetization affected infiltration and water–salt redistribution, and the magnitude of the response differed between the two water sources. Mean infiltration rate increased by 11.6–13.9% under magnetization relative to non-magnetized controls (p < 0.001), and infiltration duration decreased by 6.1–7.1% (p = 0.020), with no significant difference between the 3500 and 5000 Gs treatments (p = 0.903). The water source × magnetic intensity interaction was not significant for infiltration rate or duration. Salt storage in deep layers was reduced under magnetized treatments: by 24.74% at 40–50 cm under HW at 5000 Gs and by 29.18% at 50–60 cm under DW at 3500 Gs (both p < 0.05 relative to the respective non-magnetized controls). Magnetized irrigation was associated with reduced Na⁺ and Cl⁻ accumulation in the 0–30 cm layer and with a higher relative proportion of Ca²⁺ and Mg²⁺ in the soil water extract. These findings provide experimental evidence on how the response to magnetized irrigation varies with irrigation water source in undisturbed saline–alkali soils and support further evaluation of subsurface drainage water reuse in salinized farmland.