Statistical analysis
SPSS®11.0 (SPSS Inc.) was used for the statistical
analysis. Preliminary analysis was first conducted and
indicated that the soil data were normally distributed.
Therefore, parametric statistics of ANOVA analysis
were used to test the significance among the agricultural
land use types at p < 0.05. If the effects of agricultural
land use types are significant, mean separations were
achieved by using a protected least significant difference
(LSD) test at p < 0.05.
following the order of vegetable field > orchard > cropland
in the soil depths from 0 to 25 cm (Table 2). There
are no significant differences between orchard and vegetable
field. However, for the soil depths of 0–25 cm, the
TP contents in vegetable field are significantly higher
than that in the cropland. For the deeper soil layers
(40–70 cm), the TP is significantly higher in orchard
than that in the other two agricultural land use types (p <
0.05).
Following the same pattern as observed for the SOC
and TN, the TP contents in each agricultural land use
type decrease generally with soil depths increase, in particularly
in the soil profile of 0–40 cm (Table 2). Correspondingly,
the TP contents in the depths of 25–100 cm
range from 0.51 to 0.70 g/kg in these land use types.
The available phosphorus in vegetable field is the
highest (Table 3), corresponding well to the highest P
fertilizer inputs and frequent irrigation (Table 1). In the
depths from 0 to 40 cm, the available phosphorus contents
in vegetable field range from 22.03 mg/kg to 66.10