The low ECEC (7.48 cmol kg21) observed in the control plot 12 WAP
(Table 9) compared to its initial level of 9.80 cmol kg21 (Table 2) could be attributed to extraction by crops and heavy rainfall, hence leaching of the
cations and perhaps reaction with soil colloids without replenishment.
The exchange acidity (EA) did not follow any specific trend compared
with the ECEC, which gradually increased from 7.48 cmol kg21 in the
control plot to 13.82 cmol kg21 in the plot treated with optimum level of
RHA (Table 9). Although very highly variable, the EA and ECEC had relatively
strong positive linear correlations with increase in the rate of RHA;
r ¼ 0.56 for EA and r ¼ 0.73 for ECEC (Table 9).