The average soil pH was shown in Fig.1. Statistical analysis
revealed that fertilization treatments led to a significant increase in
soil pH compared with the CK treatment (P,0.05). The soil pH
was the lowest in CK with an average of 5.33 units and highest in
NPK treatment with 5.89 units. In OM. treatment, the soil pH
was relatively higher than CK (reaching 5.63 units).
During 1998 to 2009, the soil pH in NPK treatment appeared
relatively stable despite some slight drop with the time (Fig.2).
However, the values in other treatments showed a clear decline
trend with time despite some variations. In the beginning years
after fertilization, there was no evident difference in pH among all
treatments, but eventually the soil pH in CK reduced dramatically
and declined sharply from 5.71 to 5.03 (0.68 units lower). In SR,
GM and OM treatments, the soil pH values declined by 0.57, 0.57
and 0.27 units respectively during the experimental period.