Liming power of different particle fractions of biochar

The alkalinity given to many biochars by the ash content can be exploited for neutralizing the acidity of peat. Moreover biochar can give to growing media additional benefits, promoting water and nutrient retention and availability, and darkening pale substrates. We studied the effectiveness of an alkaline biochar from pine wood (pH 10.2) in correcting the acidity of a white peat (pH 4.2) both on the 0-10 mm biochar (B0) and on three particle-sized fractions (B1=10-6 mm; B2=6-3.3 mm; B3=<3.3 mm). Seven volumetric percentages of B0 (0, 2.5, 5, 10, 20, 30 and 40%) were tested. The doses 30% and 40% of B0 were the most effective in adjusting peat pH to moderate acidic values and they were used in assessing the role of particle size on liming ability of biochar. The 22 days incubation trial showed that stabilization occurred after 14 days incubation and that the finest fraction had the highest neutralizing power. A comparison between the liming effect of biochar and of calcium carbonate was also performed. We showed that additional benefits of biochar include physical properties such as an increase in air content, a reduction in water availability and a lower shrinkage. These preliminary results suggest that biochar can be used in place of lime in peat based growing media.