Soil pH was
determined in a 1: 1 ratio of soil:water; soil organic carbon by using
Walkley method (Walkley, 1947); extractable P by using Bray 2
(Bray and Kurtz, 1945); extractable N by extracting in phosphate
buffer solution (Ogawa et al., 1992); cation exchange capacity and
exchangeable bases by using ammoniumacetate extract method at
pH5.0 and 7.0 (Soil and PlantAnalysis Council, 1999); soil texture by
using pipette method (Soil and Plant Analysis Council, 1999). For
biochar, total carbon and nitrogen content was analyzed with a
tracer mass spectrometer (Tracer Mat, Thermo Quest Co. Ltd.,
Tokyo). Respective properties of biochar and top-soils are shown in
Table 1a and b, respectively.