The effects of biochar on ryegrass growth and microbial diversity in ionic rare earth tailings soil

Ionic rare earth tailings attract considerable attention due to a series of problems related to soil degradation. Biochar has been widely proposed for soil remediation because its favorable sorption capacity and potential nutrient supply. However, the relationships between soil microbial communities in ionic rare earth tailings and biochar amendment have been rarely studied. In this study, the effects of biochar on ryegrass growth and microbial communities were systematically studied. The results indicated that biochar had significant positive effects on the growth of ryegrass, potentially due to increased soil pH and availability of nutrients. The application of biochar resulted in a profound increase in soil organic matter, which was 8.7 to 26.3 times greater than that in the control. Microbial analysis indicated that the relative abundances of plant pathogens (Rhodanobacter and Ralstonia) were substantially decreased, while Sphingomonas and Arthrobacter increased, which likely contributed to the improved phosphorus availability for plant growth. Based on FAPROTAX and FUNGuild analyses, biochar application at 3 %-5 % significantly enhanced ryegrass growth by increasing soil pH, nutrient availability, and promoting beneficial phosphorus-solubilizing bacteria while suppressing plant pathogens. The results of this research will help reveal the biotic and abiotic response mechanisms to biochar in ionic rare earth tailings soil.