Improving available phosphorus in acidic soil using biochar

Understanding of phosphorus (P) retention and release mechanisms provides crucial information for the effective management of phosphorus to enhance crop production and sustain soil. In acidic soil, available phosphorus is fixed by aluminum and iron. To overcome this problem, soils are limed to fix aluminum and iron. But this practice is not economical for small scale farmers and also it is not environmentally friendly. This study was conducted to improve phosphorus availability using biochar produced from coffee husk and corn cob to fix aluminum and iron instead of phosphorus. Acidic soil samples were mixed with biochar applied at the rates of 0, 5, 10 and 15 t ha-1 and incubated in laboratory for 2 months at ambient temperature. The results showed significant effects (p<0.01) on selected soil chemical properties by increasing soil pH and reduced exchangeable acidity, exchangeable aluminum, and exchangeable iron in a way that enhanced the availability of phosphorus. Due to the incorporation of biochar the available P level increased to a level ranging 3.64±0.34 -23.21±0.07 mg/kg after an incubation period of 2 months and it increased by 84.3% available phosphorus when coffee husk biochar produced at 500°C temperature was applied at a rate of 15t/ha.  Moreover, further field researches are needed to evaluate the effect of biochar on availability, the fate and uptake of available P in soil.   Key words: Fixation, biochar, feedstock, acidic soil, pyrolysis temperature.