Soil salinization is a major factor threatening global food security. Soil improvement strategies are therefore of great importance in mitigating the adverse effect of salt stress. Our study aimed to evaluate the effect of biochar (BC) and nitric acid-modified biochar (HBC) (1%, 2%, and 3%; m/m) on the properties of salinized soils and the morphological and physiological characteristics of pakchoi. Compared with BC, HBC exhibited a lower pH and released more alkaline elements, reflected in reduced contents of K+, Ca2+, and Mg2+, while its hydrophilicity and polarity increased. Additionally, the microporous structure of HBC was altered, showing a rougher surface, larger pore size, pore volume, specific surface area, and carboxyl and aliphatic carbon content, along with lower aromatic carbon content and crystallinity. Moreover, HBC application abated the pH of saline soil. Both BC and HBC treatments decreased the sodium absorption rate (SAR) of saline soil as their concentration increased. Conversely, both types of biochar enhanced the cation exchange capacity (CEC), organic matter, alkali-hydrolyzable nitrogen, and available phosphorus and potassium content in saline soils, with HBC demonstrating a more potent improvement effect. Furthermore, biochar application promoted the growth-related parameters in pakchoi, and reduced proline and Na+ content, whilst increasing leaf K+ content under salt stress. Biochar also enhanced the activity of key antioxidant enzymes (superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)) in leaves, and reduced hydrogen peroxide (H2O2) and malondialdehyde (MDA) content. Collectively, modified biochar can enhance soil quality and promote plant growth in saline soils.

Salt damage affects crop yields and wastes limited water resources. Implementing water-saving and salt-controlling strategies along with amendments can enhance crop productivity and support the development of salinized soils towards. In this study, we used Jia Liang 0987 maize as the test material, and a two-factor split block design was executed to investigate the effects of synergistic management of irrigation volume (W1: 360 mm, W2: 450 mm, and W3: 540 mm) and amendments (T1: microbial agent 816.33 kghm-2, T2: humic acid 6122.45 kghm-2, T3: microsilica powder 612.25 kghm-2) on water, salt and soil indices, and growth characteristics. The combination of 450 mm of irrigation with humic acid (W2T2) or with microsilica powder (W2T3) significantly lowered the groundwater level by 0.24 m and 0.19 m, respectively. The soil mineralization was significantly reduced by 2.60 g/L and 1.75 g/L with W2T2 and 540 mm of irrigation combined with humic acid (W3T2), respectively. The soil moisture content increased with depth and over time, showing the greatest improvement with W2T2. This combination also showed optimal results for pH and total salt, organic matter, available phosphorus, quick-acting potassium, Cl-, and SO42- contents. W2T2 and W3T2 improved soil field capacity and HCO3- contents, and significantly increased total nitrogen and phosphorus content, improving the soil nutrient grade. W2T2 showed the greatest maize plant height (323.67 cm) and stem thickness (21.54 mm for diameter), enhancing above-ground dry biomass (72,985.49 kghm-2) and grain yield (14,646.57 kghm-2). Implementing water-saving and salt-controlling strategies with amendments effectively improved soil fertility and crop yield in salinized soils, and the amendments factor played a major role. In saline-alkali soils in the northwest of China, 450 mm of irrigation combined with humic acid is especially helpful for enhancing soil fertility and maize productivity.

Salinized soil is an important reserved arable land resource in China. The management and utilization of salinized soil can safeguard the current size of arable land and a stable grain yield. Salt accumulation will lead to the deterioration of soil properties, destroy soil production potential and damage soil ecological functions, which in turn will threaten global water and soil resources and food security, and affect sustainable socio-economic development. Microorganisms are important components of salinized soil. Microbial remediation is an important research tool in improving salinized soil and is key to realizing sustainable development of agriculture and the ecosystem. Knowledge about the impact of salinization on soil properties and measures using microorganisms in remediation of salinized soil has grown over time. However, the mechanisms governing these impacts and the ecological principles for microbial remediation are scarce. Thus, it is imperative to summarize the effects of salinization on soil physical, chemical, and microbial properties, and then review the related mechanisms of halophilic and halotolerant microorganisms in salinized soil remediation via direct and indirect pathways. The stability, persistence, and safety of the microbial remediation effect is also highlighted in this review to further promote the application of microbial remediation in salinized soil. The objective of this review is to provide reference and theoretical support for the improvement and utilization of salinized soil.