According to the analysis data of 173 sampling points in 1982 and 117 sampling points in 2002

the temporal-spatial variability of soil available phosphorus (SAP) of the topsoil(0~20 cm) in Chengdu Plain was expressed by spherical semi-variance model and the ordinary Kriging interpolated method. The results indicated that the average content of SAP changed from 7.1 mg/kg in 1982 to 14.3 mg/kg in 2002

with an increase of 103.40%. Influenced by the differences of agricultural management

the land use type and the soil granule contents during the past 20 years

SAP content of 75.86% of the plain area increased

respectively

which presented decreasing trend from the east to the west. The results of correlation analysis between SAP content and soil particle composition showed that

in 1982

there were highly significant negative correlation between the SAP and soil sand particle (20.02mm) content

and highly significant positive correlation between the SAP and soil clay particle(<0.002 mm)

while no significant correlation between the SAP and soil silt particle(0.020.002mm). The case was different in 2002

SAP was significantly negatively correlated with soil sand particle content

and highly significantly positively correlated with soil silt particle content

while not significantly correlated with soil clay particle content.