Objective Long-term effects of biochar application on soil acidity amelioration and microbial community at tea plantations were studied.

Method A three-year field positioning experimentation was conducted with the applications on the planting lots of corn straws-derived biochar at the rates of 0 (CK), 5 t·hm⁻² (5T), 10 t·hm⁻² (10T), and 20 t·hm⁻² (20T). Lasting effects of the applications on physicochemical properties and microbial community in soil of the tea plantations were determined by analyses and 16S rRNA gene high-throughput sequencing.

Result After three years of continuous biochar application, the physicochemical properties of the soils were significantly improved. The pH increased from a low of 4.28 to a high of 4.89, and so did the cation exchange capacity as well as the contents of organic matter, available phosphorus, and available potassium. The changes significantly enriched the alpha diversity of the microbial community with higher Chao1 and Shannon indices. They also drove a profound succession in the microbial structure showing an elevated relative abundance on the dominant phyla Proteobacteria and Actinobacteriota accompanied by a significant decline on acidophilic Acidobacteriota. As indicated by the redundancy analysis, soil pH and dissolved organic carbon (DOC) were the most critical environmental factors that led to the positive changes.

Conclusion Applying corn straws-derived biochar in an acidified soil at tea plantations proved to be an effective means to achieve a dose-dependent and lasting effect in curtailing otherwise deteriorating soil at the tea plantations. The underlining mechanism that reshaped the microbial community and improved the ecosystem was attributed to the rises on pH and DOC in soil from the biochar application as well.