Objective  In order to examine the amelioration effects of the biochars generated from canola straws planted in different soils, the acidity and pH buffering capacity (pHBC) were determined in two red soils.

  Method  Red soils mixed with different rates of canola straw biochars and then incubated for 30 days. Soil pH, pHBC, exchangeable base cations, and exchangeable acidity before and after incubation experiment were tested.

  Result  The addition of canola straw biochars significantly increased soil pH, pHBC, exchangeable base cations and significantly reduced the content of soil exchangeable acidity, which suggested that canola straw biochar cannot only ameliorate soil acidity, but also increase the resistance of red soils to acidification and inhibit soil re-acidification. The biochar generated from canola straw planted in alkaline soil showed a greater amelioration effect on soil acidity and better improvement on soil pHBC than that planted in acidic soil, which was consistent with the fact that the alkalinity and number of functional groups of the biochar generated from canola straw planted in alkaline soil were greater than that in acidic soil. At addition rate of 5%, the pH values of soils in Hunan and Huaian were increased by 37.4% and 22.4%. Correspondingly, the pHBCs of them were increased by 41.4% and 37.3%.

  Conclusion  The biochar generated from canola straw planted in alkaline soil was a better amendment for acidic red soils than that planted in acidic soil.