Decarbonized coal gasification slag (DCGS) is a coal-based solid waste generated from raw coal through the processes of gasification and decarbonization. However, the excessive production of DCGS has caused large-scale environmental problems and seriously affected the sustainable development of coal chemical enterprises. It's urgent to explore a high-value utilization approach. Here, a field trial was conducted to evaluate the feasibility of soil amendment using DCGS in a sandy soil. The 16S rRNA gene sequencing, soil quality approach and partial least squares path modeling were used to assess the responses of soil properties and relative forage value (RFV) of Leymus chinensis to DCGS addition in soil-plant-microbe system. Results showed that DCGS addition significantly increased soil pH, soil organic carbon (22.4 %), alkaline phosphatase (ALP) enzyme activity (16.5 %) and α-diversity of bacterial communities (1.37 %). Soil microbial biomass CNP in DCGS1, DCGS2, DCGS3 and DCGS4 treatments were 10.7 %, 21.3 %, 44.8 % and 69.1 % higher than control check (CK) treatment, respectively. Our study emphasized the β-diversity of bacterial communities and topological parameters of microbial co-occurrence networks were significantly altered after DCGS addition. Ultimately, higher soil quality and RFV of Leymus chinensis were obtained in DCGS addition treatments rather than the CK treatment (p < 0.01). Moreover, soil pH and p_Methylomirabilota were identified as the crucial factors affecting soil quality, while soil ALP and p_Entotheonellaeota were key factors affecting RFV of Leymus chinensis according to Mantel test. Our result further evidenced that there were relatively low ecological risk level after DCGS addition (Ecological Risk Index < 150), thus DCGS addition was considered as a potential method in improving soil quality. Taking into account the impact of DCGS addition on soil microbial community, soil quality, and ecological safety, the recommended application rate for sandy soil is 60 t·ha^-1 (DCGS3). Our findings elucidate that soil amendment with DCGS not only enhance soil quality and RFV of Leymus chinensis, but also provide potential possibility for safe and environmentally friendly utilization of DCGS. These findings deepened our understanding of sustainable development and efficient management of DCGS.

Chemical and plant-based strategies have become increasingly critical for the remediation of saline–alkali soils. However, the underlying mechanisms driving improvements in soil quality and ecological functionality remain insufficiently understood. In this study, we adopted a synergistic remediation approach that integrated multiple switchgrass (Panicum virgatum L.) cultivars with a coal-based soil amendment to enhance saline–alkali land. A field experiment was conducted using five switchgrass varieties (YM-1, YM-2, YM-3, YM-4, and YM-5), each receiving a uniform application of the coal-based soil conditioner at 10 t ha⁻¹. A traditional control group was not included in this study, as the experimental design focused on direct comparisons between varieties. Our results showed that soil ionic composition played a significant role in shaping microbial activity. Notably, we found that YM-5 treatment exhibited the highest relative soil microbial abundance (22.1%) under the condition of soil amendments. Furthermore, the YM-5 treatment significantly reduced soil Na+ content and exchangeable sodium percentage (ESP) (p < 0.05), outperforming other treatments. Compared to YM-2, the YM-5 treatment also resulted in substantial increases in soil organic carbon (SOC) and available potassium (AK), increases of 78.28% and 54.3%, respectively. In addition to enhancing physicochemical parameters, the integration of switchgrass and amendment promoted soil biological vitality. For example, the YM-2 treatment achieved a 7.4% increase in catalase (CAT) activity and a 6.3% reduction in soil pH compared to YM-3, indicating improved redox balance and acid–base regulation. Collectively, these findings provide direct empirical evidence supporting the effectiveness of switchgrass–amendment combinations in saline–alkali soil restoration. Among the tested cultivars, YM-5 demonstrated superior ecological performance and is recommended as the most suitable genotype for saline–alkali soil amelioration when used in conjunction with coal-based amendments.