Abstract: Acidification of tea garden soil is an important factor that restricts sustainable production of tea plants. Field plot experiments were conducted to study the effects of several improvement measures on acidified tea soils, which would provide scientific basis to improve the soil quality. The experiment involved several treatments: (1) pure chemical fertilizer (routine fertilization, NPK), (2) chemical fertilizer plus 10 t•hm^-2 biochar (NPK+BC10), (3) organic manure substituted 50% of chemical fertilizer (OM50), (4) organic manure substituted 50% of chemical fertilizer plus lime (OM50+Lime), (5) organic manure substituted 50% of chemical fertilizer plus 10 t•hm^-2 biochar (OM50+BC10), (6) organic manure substituted 50% of chemical fertilizer plus 20 t•hm^-2 biochar (OM50+BC20), and (7) organic manure substituted 50% of chemical fertilizer plus 40 t•hm^-2 biochar (OM50+BC40). After two years of continuous application, soil samples were taken to determine the soil acidity, the nutrient contents, and the microbial community. The microbial community structure was measured using phospholipid fatty acid (PLFA) and Biolog technology. Compared with NPK, soil pH were significantly increased by 1.10, 0.49 and 0.68 units, and base saturation were significantly increased by 114.01%, 55.92% and 58.62% in OM50+Lime, OM50+BC20, and OM50+BC40 treatments, respectively. Compared with NPK, soil organic carbon contents under OM50+BC10, OM50+BC20 and OM50+BC40 treatments were significantly increased by 29.68%, 41.04% and 59.37%, respectively. All treatments had no significant effect on soil nitrate nitrogen content, while the ammonium nitrogen contents under OM50, OM50+BC20 and OM50+BC40 treatments were significantly increased by 40.27%, 44.77% and 41.77% compared with NPK. NPK+BC10, OM50+BC10, OM50+BC20 and OM50+BC40 significantly increased soil microbial activity, species richness, diversity and homogeneity of microbial community. OM50+BC10, OM50+BC20 and OM50+BC40 treatments significantly reduced the ratios of fungi to bacteria, indicating that they increased the stability of soil ecosystem in the short term. The ratio of gram-negative bacteria to gram-positive bacteria under OM50+Lime treatment was significantly lower than that under NPK, which indicates that soil microorganism under OM50+Lime suffered the greater environmental stress than that under other treatments. In summary, OM50+Lime, OM50+BC20 and OM50+BC40 had obvious improvement effect on acidified tea garden soil, while OM50+BC20 and OM50+BC40 had better improvement effect on soil microbial community properties than OM50+Lime. Simultaneous considering ameliorative effect and cost of economy, OM50+BC20 was the best improvement scheme.

Key words: tea garden soils, acidification, soil microbial community, biochar, lime, organic manure