Spatial distribution and variability of main soil physical and chemical properties in Chongming and affecting factors.

A total of 128 soil samples were collected from the 0-20 cm topsoils of the three islands of Chongming,Shanghai,using the classical statistics and geostatistics for analysis of soil organic matter,total nitrogen,available phosphorus,available potassium,soil electrical conductivity,soil bulk density and pH,and for further study of spatial variation of the physical and chemical properties.Results show that the spatial variabilities of available potassium and soil electrical conductivity were strong,that of pH was weak,and the others were moderate.Soil bulk density and pH demonstrated a strong spatial correlation while soil organic matter,total nitrogen,available phosphorus and available potassium did not,which shows their distributions are strongly affected by stochastic factors.The Kriging interpolation analysis revealed that the distributions of soil organic matter and total N were affected by farming practices and urbanization with high values found in the areas where human activities were intensive.Soil bulk density and pH were in a similar trend,decreasing gradually from the east and west tips of the island to the center.Soil organic matter,total nitrogen and available potassium in Chongming island were significantly correlated(α=0.01).