A five-year successive rice straw-derived biochar(BC) amendment pot trial was conducted to investigate the BC effects on crop growth responses,soil properties and ammonia volatilization in a calcareous alkaline soil from 2010-2015 under the greenhouse condition. We adopted 0(the control; BC_0),2.25 t·hm~(-2)(BC_(2.25)) and 22.5 t·hm~(-2)(BC_(22.5)) for each wheat/millet crop season with an identical dose of NPK fertilizers. The results showed that BC treatments(BC_(2.25) and BC_(22.5)) improved soil fertili...