2.5. Soil properties measurement after incubation
After incubation, soil exchangeable acidity and exchangeable
Al3+ were measured by titrating with 0.25M NaOH to pH of
7.0 after extraction by 1.0M KCl. Soil CEC was measured with the
ammonium acetate compulsory displacement method (Penget al., 2011). Soil exchangeable base cations were extracted by
1.0M ammonium acetate (pH 7.0). Then, Ca2+ and Mg2+ contents
were measured with atomic absorption spectrometry (AA-700,
PerkinElmer, USA), and K+ and Na+ contents were measured with
flame photometry (FP640, Shanghai Precision Instrument Co.,
China) (Pansu and Gautheyrou, 2006).