The application of biochar to improve the quality of saline soils has attracted widespread attention. However, the impact of saline soil amendments with biochar prepared at different pyrolysis temperatures remains unclear. Therefore, we conducted a two-year (2022–2023) field experiment in the Hetao Irrigation District, China, to evaluate the effects of the biochar pyrolysis temperature (C1: 300 °C, C2: 500 °C, and C3: 700 °C) and application rate (T1: 10 t/ha and T2: 20 t/ha) on the soil quality and maize yield. The results indicated that (1) all biochar treatments significantly decreased the soil bulk density and increased the soil porosity; (2) treatment C3T1 significantly increased the soil moisture content and decreased soil salinity. The C3T2 treatment significantly increased the soil’s organic carbon content, and the soil’s available phosphorus content was greatest in the C1T2 treatment. (3) The maize yield increased linearly with the soil quality index (SQI), which was attributed mainly to improvements in the soil water–salt conditions and increases in the soil organic carbon content. In summary, biochar produced at high pyrolysis temperatures, when applied at a low application rate (C3T1), can result in high corn yields and improve saline soil quality.

The northern foothills of Yinshan Mountain are situated in northern China’s agricultural and pastoral ecotone, serving as a crucial ecological barrier. To comprehensively assess the impact of grassland resource restoration in this region since the initiation of the Grain-for-Green conversion project in 2000, this study analyzes the spatiotemporal characteristics of precipitation use efficiency (PUE) and investigates climate-driven factors during 2001–2021. The results showed that the grassland types at the north foot of Yinshan could be divided into four categories: warm-arid, warm subtropical semidesert (WSS), warm temperate-arid, warm temperate zonal semidesert (WZS), warm temperate-semiarid, warm temperate typical steppe (WTS), and warm temperate-subhumid forest steppe (WFT). The NPP of the four grassland species were 151.34 (WSS), 196.72 (WZS), 283.33 (WTS), and 118.06 gC·m⁻² (WFT), and correspondingly, the PUE of the four grassland species were 0.66 (WSS), 0.66 (WZS), 0.80 (WTS), and 0.57 gC·m⁻²·mm⁻¹ (WFT). From 2001 to 2021, PUE in grassland showed an overall upward trend, rising from 0.57 to 0.99 gC·m⁻²·mm⁻¹. The trend analysis found that the vegetation ecological area of the northern foot of Yinshan became better, of which 54.36% was improved and 15.72% was degraded. It is worth pointing out that WSS had the highest degree of improvement, while WFT was in a degraded state. The climate driving force analysis shows that the regional contribution of precipitation is 19.57%, temperature is 28.33%, potential evapotranspiration is 13.65%, wind speed is 10.79%, and saturated vapor pressure is 27.66%.

This study aimed to explore the characteristics of water and salt transport in saline-alkali grassland, effectively guide the ecological construction of saline-alkali grassland along the Yellow River in western Inner Mongolia, and provide a theoretical basis and technical support for the ecological restoration of saline-alkali grassland and regional environmentally sustainable development. The desalination process of saline-alkali soil under the condition of subsurface pipe drainage was simulated using an indoor soil tank test. The variation in soil leaching water consumption, the salinity of the leaching filtrate with time, the accumulation of the filtrate, and the desalination rate of the filtrate under the condition of continuous leaching with a 25 mm head were analyzed. At the same time, the variation process of soil conductivity at 0~40 cm (upper layer), 40~80 cm (middle layer), and 80~120 cm (lower layer) was analyzed. Subsurface pipe drainage can reduce the soil salt content, while reducing the control area of the subsurface pipes can accelerate the soil desalination rate, thus improving the quality of saline-alkali soil. In addition, the leaching effect under 30 cm partition spacing was better than that under 35, 40, and 45 cm partition spacing, and the corresponding desalination rate was higher. Under stable continuous leaching with a 25 mm head, the entire leaching process can be divided into three stages: the rapid desalination, moderate desalination, and stable stages. During the desalination process, the upper, middle, and lower layers were desalinated synchronously, and the desalination rate of the upper layer was the highest, followed by the desalination rate of the middle and lower layers.

[Objective] Soil microorganisms are the most active parts in soil and are sensitive to soil additives. This study aimed to clarify the impacts of the addition of biomass materials (corn straw and biochar) and nitrogen application on the compositions of the soil microbial community in moderately saline soils (salt content was 0.4%). [Method] Indoor constant-temperature cultivation experiments were conducted to study the effects of biomass materials and nitrogen application on the microbial diversity and community structure in moderately saline soils. This experiment had a two-way factorial design, with the biomass materials and nitrogen application rates as the treatments. The biomass materials included no addition of biomass materials as a control (C0), corn straw (C1, 0.64 g/pot), and biochar (C2, 0.85 g/pot), and the nitrogen application rates included 0 g N (N0), 0.015 g N (N1), and 0.03 g N (N2). There were nine treatments, as follows: C0N0, C0N1, C0N2, C1N0, C1N1, C1N2, C2N0, C2N1, and C2N2. [Results] (1) The different biomass materials and nitrogen application levels significantly influenced the α-diversity and composition of the bacterial community. At the initial stage of cultivation, the soil bacterial diversity was relatively high, and it significantly decreased after 35 days of cultivation. Moreover, the improvement of the bacterial community structure by the biochar treatment was better than that of corn straw. After 35 days of cultivation, the relative abundance of Actinobacteria, Bacteroidetes, and Firmicutes in the soil significantly increased, while the relative abundance of Gemmatimonadete, Chloroflexi, Acidobacteria, Planctomycetes, and Patescibacteria significantly decreased. Ammonium nitrogen, nitrate nitrogen, and nitrate reductase were the main environmental factors affecting the bacterial community. (2) The different biomass materials and nitrogen treatments significantly affected the richness of the fungal communities. The fungal richness index significantly increased after adding the corn straw and biochar treatments, and the addition of corn straw promoted an increase in the beneficial bacterial abundance in the moderately saline soil. Soil nitrate reductase and ammonium nitrogen were the main environmental factors affecting the fungal community. [Conclusions] In summary, biomass materials and nitrogen application can effectively increase the diversity of soil microbial communities and optimize the structure of microbial communities, thereby ameliorating the ecosystem health of moderately saline soil.

Microorganisms adapt to saline environments by utilizing energy to produce organic osmolytes. However, their energy requirements may fluctuate with varying soil salinity levels. The study focused on maize cultivation in soils with slight and moderate salinity (S1 and S2; Electrical Conductivity [EC] of 0.46 and 1.07 dS∙m^-1 , respectively). Six treatments were applied: CK (no fertilization); U1 (urea); and U₃O₁, U₁O₁, U₁O₃, and O1, where different proportions of urea nitrogen were substituted with organic fertilizers. As soil salinity increased, soil microbial biomass and microbial activity decreased. MBC, MBN, and soil respiration flux were 12.01%-68.81%, 14.31%-58.58%, and 11.75%-54.71% lower in the S₂ soil than in S₁ soil. In both soils, soil microbial biomass and microbial activity were significantly increased when the appropriate proportion of organic fertilizer was applied. MBC, MBN, in the S₁ soil were higher under U₁O₁ treatment than under U₁ treatment—by 48.44%, 42.50%, and 31.74%, respectively (P ⪅ 0.05). In the S2 soil, MBC, MBN, and soil respiration flux were significantly higher under O₁ treatment than under U₁ treatment—by 68.07%, 48.99%, and 45.19%, respectively (P ⪅ 0.05). Correlation analysis revealed significant positive correlations between soil respiration and soil microbial biomass (P ⪅ 0.01). Soil temperature and nitrogen content were positively correlated with soil respiration and soil microbial biomass (P ⪅ 0.05).