Biochar Effects on Soil Chemical Properties, Microbial Communities, Tea Quality and Yield in a Strongly Acidic Tea Plantation: A Field Study

Soil acidification severely threatens soil health, tea quality and yield in tea plantations, making it essential to use appropriate soil amendments to address this issue. Biochar can enhance the agricultural soil environment, but its effects on microbial communities, soil fertility, tea quality and yield remain incompletely understood. In this field study, three treatments were applied in a strongly acidic tea plantation: CK (traditional fertilization), BC1 (CK with 4.5 t ha−1 biochar) and BC2 (CK with 9 t ha−1 biochar). Soil chemical properties, microbial communities, tea quality and yield were measured, and their correlations were analyzed. Compared with CK, BC2 significantly increased soil pH from 4.25 to 4.58 and elevated soil total carbon, total nitrogen and ammonium nitrogen by 99.18%, 21.29% and 166.67%, respectively. The BC2 treatment also enhanced soil microbial diversity and increased the relative abundance of potentially beneficial bacterial genera, which were positively correlated with improved tea quality and yield. In particular, BC2 increased free amino acids, water extracts (WE) and tea yield by 10.64%, 13.01% and 13.65%, respectively. Applying biochar at 9 t ha−1 combined with traditional fertilization appears to be a promising management practice under the conditions of this study to improve soil conditions, tea quality and yield in strongly acidic plantations.