Abstract:  Effect of biochar addition on pH and nitrogen transformation in the acidic red and yellow soils at tea plantations was studied by an aerobic incubation experiment in the lab. Biochar made from clipped tea branches was added to the soils at a rate of H0(0t·hm^-2), H1(8t·hm^-2), H2(16t·hm^-2),H3(32t·hm^-2), or H4(64t·hm^-2). The results showed that, the pH of the red soil raised 0.24 to 1.20 units and that of the yellow soil raised 0.26 to 1.34 units with the biochar. On the other hand, the nitrogen mineralization, net nitrogen mineralization rate, and net mineralization rate, especially the NO₃⁻-N content, of the soils were significantly reduced. The nitrification in soil was inhibited by the additions, and the effect was greater with increasing biochar. Since the nitrogen mineralization, and the rates of mineralization of the red soil were higher than those of the yellow soil, which showed a negative net reduction with the biochar additions, it indicated that a same biochar application would result in much greater effection the nitrogen transformation in the red than the yellow soil. It appeared that, depending upon the application rate and the soil type, by incorporating biochar varying degrees of the inhibitory effect on the nitrogen mineralization and nitrification in the plantation soils could be achieved.