Effect of biochar-doped rare earth tailing on soil properties and plant growth in reclaimed shale gas sites

The soil in reclaimed shale gas sites is compacted and suffers from issues like poor drainage, drought conditions, and nutrient deficiency, posing challenges for agricultural production. In this study, rare earth tailings were incorporated into biochar at different mass ratios (rare earth tailings: biochar = 1:1, 1:2, 1:3, 1:4). Subsequently, a series of rare earth tailings-doped biochar materials (REE-BC) were prepared by calcination at 700°C. The impact of REE-BC on the soil in reclaimed shale gas sites was evaluated by pot experiment. The results showed that the pH, moisture content, nutrients (N, P, K), organic matter, and enzyme activities in the treated soil were all increased, while the soil bulk density was decreased. At the same time, the chlorophyll, soluble sugar, soluble protein, and activities of antioxidant enzymes in Chinese cabbage were increased, while the malondialdehyde content was decreased. Additionally, FT-IR analysis detected an absorption peak at 550 cm−1, indicating the successful loading of Ce onto the biochar. SEM-EDS and BET analyses showed that the biochar modified by secondary pyrolysis had a larger specific surface area and pore volume, which was conducive to increasing soil porosity and water retention. This study demonstrates the potential of REE-BC in improving soil properties and promoting Chinese cabbage growth, providing theoretical basis for novel approach for reclaiming shale gas-affected soils.