Effects of biochar on growth and yield of rice in an acidic paddy field: findings from a five-year field trial

Biochar has been widely suggested as an effective amendment to improve crop growth and productivity. However, its long-term effects on rice growth and productivity, especially in acidic paddy are less understood. We conducted a five-year(2015-2019) field experiment with the single factor randomized block design in an acidic paddy of Changsha, Hunan Province, south China. We aim to investigate(1) how do rice growth and productivity respond to different amount of biochar amendment(i.e., 0 t/hm~2(CK), 20 t/hm~2(B20), 40 t/hm~2(B40), 60 t/hm~2(B60), 80 t/hm~2(B80), and 100 t/hm~2(B100)) and(2) how long can the effects of biochar amendment sustain? The results showed that:(1) leaf area index(LAI), the chlorophyll content of the reciprocal fourth leaf, and dry matter accumulation at the heading stage increased with the increasing amount of biochar amendment, so did the rice yield.(2) Biochar amendment showed no significant effects on the chlorophyll content of the flag leaf at the heading stage and the grain-leaf a