DOC, CHS extracted with 0.1 mol L-1 NaOH, and CFA from the NaOH extraction at pH 1.0 were determined by potassium dichromate oxidic method (Pereira et al. 2006).
CHA was calculated as the difference in CHS and CFA. Activities of urease and AlkP were measured according to Cang et al. (2009).