Biochar application is an important measure to regulate SOC. However, the effects of biochar application on soil respiration and SOC fraction of the saline soil have been scarcely investigated. Therefore, in this study, we monitored the annual SOC, nutrients, temperature, water content, and respiration rate under three maize-straw-derived biochar application doses (0, 15, and 30 t∙hm⁻²). Biochar enriched the soil in terms of fast-acting potassium and phosphorus, alkali-hydrolyzable N, ${\mathrm{NO}}_3^{-}$-N, and ${\mathrm{NH}}_4^{+}$-N to varying degrees. One-time biochar application in the trial year continued to fertilizer retention in the following year. Mineral-associated organic carbon and SOC contents increased with time after biochar application, whereas the changes in particulate organic carbon content were the opposite; soil respiration rate was reduced by 7.7–14.7%, and the reduction increased with the dose as well in successive years. The soil respiration rate and soil temperature showed a significant linear correlation, but the application of a high amount of biochar reduced the correlation between the two. Considering the soil respiration rate and physicochemical properties, the best biochar application rate for saline soil is suggested to be 30 t∙hm⁻². This study is of great significance for soil carbon sequestration, emission reduction in saline areas, and the realization of a “carbon peak” in the sense of farmland.

“Peak carbon and neutrality”, also known as dual carbon, is the key to solving the problems of energy and industrial low-carbon transformation, and is also fundamental to promoting the development of new industries that protect the environment and conserve resources. Among the cities along the Yellow River Basin, the city of Luoyang in Henan province is strategically vital in the coordinated development of the regional economy. Thus, researching the coupling of urbanisation and ecological protection is an important way to realise the dual carbon goal. To explore the coupling and coordination (CC) between urbanisation and the ecological environment, an index system is built for comprehensively assessing urbanisation and ecological environment (UEE) systems in Luoyang, and a coupling model to measure their coordination degree, quantitatively analyzed the CC process and evolution trend of Luoyang’s UEE, and explored the driving factors causing their changes through regression analysis. The results show that the integrated urbanisation development index of Luoyang ranges from 0.7571–0.9497; however, the contribution of the city’s population to urbanisation is the lowest at only 5.231%. Therefore, it is suggested that the government and other institutions should pay more attention to coordinating the human–land relationship when planning for urban development. The integrated ecological environment development index ranges from 0.7512–0.8266. The contribution ratio of the ecological environment state and pressure on the ecological environment is relatively high, at 27.9% and 48.7%, respectively. Therefore, the city of Luoyang city should reduce the emission of industrial pollutants and improve the environmental level. In addition, the CC degree of UEE of Luoyang ranges from 0.8131–0.9296 during 2016–2021, with an overall trend of steady increase, and the coupling correlation coefficient of R² = 0.9335, with a good overall coupling effect. The results show that Luoyang needs to further accelerate its industrial transformation and upgrading and spatial development strategy, and strive to become an environment-optimised city. This study provides scientific and practical suggestions for the CC development of urbanisation and environment in the city of Luoyang, Henan province, and has reference value for accelerating the realisation of the two-carbon strategy.

Soil secondary salinization is a major limiting factor of sustainable agricultural production in arid and semi-arid irrigation zones, yet predictive tools for regional water–salt dynamics remain limited. The Yichang Irrigation District, located within the Hetao Irrigation Area, has experienced persistent salinity challenges due to shallow groundwater tables and intensive irrigation. In this study, we aimed to simulate long-term soil water–salt dynamics in the Yichang Irrigation District and evaluate the effectiveness of different engineering and management scenarios using the SaltMod model. Field monitoring of soil salinity and groundwater levels during summer and fall (2022–2024) was used to calibrate and validate SaltMod parameters, ensuring accurate reproduction of seasonal soil salinity fluctuations. Based on the calibrated model, ten-year scenario simulations were conducted to assess the effects of changes in soil texture, irrigation water quantity, water quality, rainfall, and groundwater table depth on root-zone salinity. Our results show that under baseline management, soil salinity is projected to decline by 5% over the next decade. Increasing fall autumn leaching irrigation further reduces salinity by 5–10% while conserving 50–300 m³·ha⁻¹ of water. Sensitivity analysis indicated groundwater depth and irrigation water salinity as key drivers. Among the engineering strategies, drainage system improvement and groundwater regulation achieved the highest salinity reduction (15–20%), while irrigation regime optimization provided moderate benefits (~10%). This study offers a quantitative basis for integrated water–salt management in the Hetao Irrigation District and similar regions.

This study examined groundwater dynamics under saline–alkali improvement measures in a 3.66 × 10⁷ m² study area in Wuyuan County, Hetao Irrigation District, where agricultural sustainability is constrained by soil salinization. This work investigated the spatiotemporal evolution patterns and influencing factors of the groundwater environment in the context of soil salinity–alkalinity improvement, as well as the impact of irrigation on the ionic characteristics of groundwater. Furthermore, based on this analysis, a groundwater numerical model and a prediction model for the study area were developed using Visual MODFLOW Flex 6.1 software to forecast the future groundwater levels in the study area and evaluate the effects of varying irrigation scenarios on these levels. The key findings are as follows: (1) The groundwater depth stabilized at 1.63 ± 0.15 m (0.4 m increase) post-improvement measures, maintaining equilibrium under current irrigation but increasing with reductions in water supply. The groundwater salinity increased by 0.59–1.2 g/L across the crop growth period. (2) Spring irrigation raised the groundwater total dissolved solids by 15.6%, as influenced by rock weathering (38.2%), evaporation (31.5%), and cation exchange (30.3%). (3) Maintaining current irrigation systems and planting structures could stabilize groundwater levels at 1.60–1.65 m over the next decade, confirming the sustainable hydrological effects of soil improvement measures. Reducing irrigation to 80% of the current water supply of the Yellow River enables groundwater level stabilization (2.05 ± 0.12 m burial depth) within 5–7 years. This approach decreases river water dependency by 20% while boosting crop water efficiency by 18.7% and reducing root zone salt stress by 32.4%.

The ameliorative mechanism of biochar in reducing soil greenhouse gas emissions in arid saline farmland remains unclear. A two-year field study in sorghum farmland in China’s Hetao Irrigation District was conducted to assess the influence of corn straw-derived biochar on GHG emissions and explore the role of soil physicochemical properties in regulating GHG fluxes. Four different biochar application rates were tested: 0 (CK), 15 (C15), 30 (C30), and 45 t hm⁻² (C45). Compared to CK, C15 reduced CH₄ emissions by 15.2% and seasonal CH₄ flux by 77.0%. The N₂O flux followed CK > C45 > C30 > C15 from 2021 to 2022. C15 and C30 significantly decreased GWP, mitigating GHG emission intensity. Biochar application enhanced sorghum grain yield. Soil temperature was the primary determinant of CH₄ flux (total effect = 0.92). In the second year, biochar’s influence on CH₄ emissions increased by 0.76. Multivariate SEM identified soil moisture (total effect = −0.72) and soil temperature (total effect = −0.70) as primary negative regulators of N₂O fluxes. C40 lead to salt accumulation, which increases CH₄ emissions but inhibits N₂O emissions. Averaged over two years, GWP under C15 and C30 decreased by 76.5–106.7% and 5.3–56.1%, respectively, compared to CK. Overall, the application of biochar at a rate of 15 t hm⁻² significantly reduced CH₄ and N₂O emissions and increased sorghum yield.

Introduction: Freshwater scarcity and soil salinization constrain agricultural production in arid and semi-arid regions. Freezing saline water irrigation (FSWI) offers a potential strategy for using saline water during the freeze-thaw period, but the optimal irrigation amount and its yield-driving mechanisms remain unclear. Methods: Here, a three-year field experiment was conducted from 2022 to 2024 in Dalad Banner, Inner Mongolia, China, with four FSWI treatments of 0, 90, 180 and 270 mm. We evaluated pre-sowing soil hydrothermal, salinity and microbial functional indicators, and assessed sunflower growth, yield and seed quality under uniform agronomic management. Results: Among the treatments, FSWI180 showed the best overall performance. It maintained favorable pre-sowing soil moisture and salinity conditions, increased yield by 93% relative to the non-irrigated control, and improved seed oil content to 43.96%. It also achieved the highest comprehensive growth and quality indices, with mean GI and QI values of 2.126 and 1.182, respectively. XGBoost-SHAP analysis identified soil moisture, total salinity, electrical conductivity and community robustness as the main yield-driving factors, together accounting for 74.75% of the total contribution. Discussion: These results indicate that 180 mm FSWI can coordinate soil water storage, salinity regulation and microbial functional stability, thereby supporting stable yield improvement and high-quality sunflower production in cold arid saline-alkali regions.