In this study, the effects of biochar and compost on the amelioration of coastal saline soil were investigated through indoor leaching experiments and soil culture experiments. The results revealed that the multivoid structure of biochar and compost, when applied to soil, effectively improved soil hydraulic conductivity, promoted the leaching of salt ions, and reduced soil electrical conductivity. Owing to the high pH value of biochar and the lower pH value of compost, the combined application of the two has a complementary effect on improving the pH value of coastal saline soils. The calcium (Ca²⁺) and magnesium (Mg²⁺) contained in biochar and compost are exchanged with Na⁺ adsorbed by soil colloids, which reduces the sodium (Na⁺) adsorption ratio (SAR) value of the soil. Biochar and compost improve the physical properties of the soil, and the organic matter they contain helps soil particles aggregate with each other and form stable clusters, thus promoting the formation of soil agglomerates, which are conducive to the formation of clusters with a diameter of ≤0.25 mm. Biochar and compost are rich in nutrients, and their application significantly increased the contents of available nutrients and organic matter as well as the activities of urease, phosphatase, and dehydrogenase in saline soils. However, too high of an application rate of biochar increases the soil pH value, and excessive application of compost can lead to greater soil conductivity, which inhibits the activities of soil urease, phosphatase and dehydrogenase. Therefore, rational control of application rates is essential for improving coastal saline soils. Future research should further explore the synergistic effects of biochar and compost in improving soil structure, nutrient effectiveness, and microbial activity to promote their effective application in coastal saline–alkaline soil improvement.

Studying both soil carbon (C) and nitrogen (N) storages in different climate zones and their relationship with climatic factors is of great significance for understanding soil fertility and predicting global climate change. Climate influences soil minerals, which are important for soil organic carbon (SOC) and N retention. However, there are few studies on SOC and soil total nitrogen (STN) storage in different climatic zones, and of the effects of soil oxidation minerals on SOC and STN storage. We measured the storage of SOC and STN and the content of oxidizable minerals in soils from different climatic regions, then obtained climate data from the China Meteorological Data Service Center, and finally investigated the effects of climate factors and soil oxides minerals on SOC and STN. The results showed that climatic factors (mean annual temperature—MAT, mean annual precipitation—MAP, and ≥10 °C mean annual cumulative temperature—MACT) had significant effects on SOC and STN content, and there was significant epistatic clustering of SOC and STN contents in different climatic zones. When MAT, MAP, and MACT increased, SOC and STN storage showed a trend of increasing and then decreasing, and both SOC and STN storages were largest in the middle temperate zone. The content of soil metal oxides (Al₂O₃, Fe₂O₃, Na₂O, MgO, CaO, K₂O, and TiO₂) showed significant positive correlation with climatic factors (MAT, MAP, and MACT). The contents of Al₂O₃, Fe₂O₃, CaO, K₂O, and TiO₂ showed significant negative correlation with SOC and STN contents. In summary, our results showed that, although soil metal oxides (SMO) have a protective effect on SOC and STN to some extent, they do not change the influence of climatic factors on SOC and STN storage.

With the rapid expansion of urban green spaces and the increasing amount of domestic waste, efficient and sustainable treatment of green waste (GW) and kitchen waste (KW) has become a pressing issue. Co-composting offers a green and low-carbon solution, yet a systematic understanding of its greenhouse gas (GHG) emission dynamics remains lacking. This study aims to investigate the impact of varying GW:KW ratios on GHG emissions during composting, in order to identify optimal mixing strategies and sup-port the development of low-carbon urban waste management systems. Six treatments with different GW:KW ratios (10:0, 9:1, 8:2, 7:3, 6:4, and 5:5) were evaluated under continuous aeration for 42 days. Results showed: (1) All treatments exhibited a typical composting temperature profile (mesophilic, thermophilic, cooling, maturation), with final seed germination index (GI) > 95% and significantly reduced E4/E6 ratios, indicating maturity. (2) When kitchen waste (KW) was ≤20%, cumulative GHG emissions slightly increased; KW ≥ 30% led to net reductions, with the 6:4 treatment (A4) achieving the highest decrease (17.44%) in total CO₂-equivalent emissions. In conclusion, maintaining KW at 40–50% optimally balances compost maturity and emission reduction, providing a viable strategy for the high-value utilization of urban organic waste and carbon mitigation.

With the increasing output of coal fly ash (CFA) and garden waste, it is of great significance for environmental protection and resource utilization to establish if it can be recycled. The saline soil is widely distributed in the coastal areas of northern China, with high salt content and poor physical and chemical properties, which seriously affects the development of local agriculture and forestry and causes the waste of arable land. If CFA and garden waste compost (GWC) can be applied to saline soil improvement, it not only improves the local soil problem, but also helps environmental protection. Leaching salt is an important measure to reduce salt content in saline-alkali soil. The purpose of this study was to explore the effect of CFA and GWC on salt leaching of coastal saline-alkali soil through a soil column simulation test. The use of CFA and GWC promoted leaching and reduced leaching time. The addition of CFA and GWC to the soil suppressed the increase of HCO3- and CO32- during leaching, but increased the salt ion content of the soil after leaching. The addition of CFA to the soil reduced the ion retention of GWC in the soil, but the application of CFA and GWC had no significant effect on the leaching sequence of salt ions. CFA and GWC added to the soil improved the physicochemical properties and the quality of saline soils, but GWC was less effective than CFA in improving soil physicochemical properties. Application of CFA reduced the leaching time of soil salt ions by about 25%, as well as reduced the pH, EC, SAR, and total salt ion content of the soil by 2.18%, 20.83%, 56.63%, and 38.95%, respectively.

Soil salinization severely threatens agricultural productivity and ecosystem sustainability, particularly in coastal regions. Halophyte-based phytoremediation is a promising strategy, yet how rhizosphere soil legacy effects at different restoration ages influence subsequent plant growth and microbial communities remains poorly understood. Here, rhizosphere soils of Nitraria tangutorum at 1- (BC-1), 2- (BC-2), and 3-year (BC-3) restoration stages and non-rhizosphere bulk soil (CK) were sampled, with alfalfa cultivated as a bioindicator to assess soil physicochemical properties, plant growth, stress physiology, and rhizosphere microbiota. With increasing restoration age, rhizosphere soil shifted from a state of salt accumulation and nutrient deficiency to one of salt depletion and nutrient enrichment, with BC-3 exhibiting the highest soil organic matter, total phosphorus, and alkali-hydrolyzable nitrogen and the lowest total salt and soluble Na⁺. Alfalfa growth was suppressed in BC-1 and BC-2 soils, but significantly promoted in BC-3, accompanied by the lowest malondialdehyde and proline content, indicating effective alleviation of oxidative and osmotic stress. Microbial diversity peaked at BC-2, whereas the total proportion of halotolerant bacteria declined from 0.44 (BC-1) to 0.34 in BC-3 (significantly lower than CK), suggesting a successional shift from a stress-dominated community toward a functionally specialized consortium. Regression analyses identified soluble sodium as the variable most strongly associated with growth inhibition (R² > 0.80) for plant height and root length. We suggest soluble sodium may represent the principal factor associated with growth inhibition and that a positive-feedback loop among plant Na⁺ sequestration, microbial carbon sequestration, and soil maturation may sustain long-term saline–alkali soil improvement. These findings suggest a three-stage successional mechanism and highlight the critical role of restoration age in mediating plant–microbe–soil synergistic remediation of coastal saline soils.

Soil salinization is a major global issue that inhibits plant growth, disrupts rhizosphere microbial ecology, and compromises plant health. Utilizing salt-tolerant, plant-growth-promoting microorganisms offers a promising strategy for mitigating salt stress and improving soil productivity. In this study, a salt-tolerant, phosphate-solubilizing fungal strain was isolated from coastal saline-alkaline soil and designated as Penicillium oxalicum PF1. Its salt tolerance and phosphorus mobilizing capacity were characterized, and pot experiments were conducted to elucidate its effects on plant salt tolerance and the underlying mechanisms. The results showed it could survive up to 17 % (w/v) NaCl in culture medium and solubilized different insoluble phosphorus sources in the order Ca-P > Mg-P > Fe-P, with a maximum solubilization of 980.09 mg/L when Ca-P was supplied. Pot experiments and metagenomic analysis revealed that PF1 significantly promoted alfalfa growth in saline soil, it triggered significant restructuring of the alfalfa rhizosphere microbiome, promoting the functional transformation of rhizosphere microbial communities, thereby alleviating salt stress imposed on alfalfa. In summary, P. oxalicum PF1 exhibits robust salt tolerance and high phosphate-solubilizing activity, restructures the alfalfa rhizosphere microbiome, enhances host stress resistance, mitigates salt-induced physiological damage, and ultimately promotes plant growth in saline soil.