The Mechanisms of Soil Conditioner and Switchgrass in Improving Saline-Alkali Soil: A Field Study in a Semi-Arid Area

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.