| According to the data of organic matter (OM), total nitrogen (TN), available phosphrus (AP) and available potassium (AK) of topsoil samples (0-20cm) collected from 135 sites in 2007, the spatial distribution characteristics of the main soil nutrients in Chongming three islands (Chong-ming island, Changxing island and Hengsha island) were analyzed using the methods of geostatistics and overlay analysis in the software of ArcGIS 9.1.(1) The results showed that the contents of SOM, TN and AK were relatively low in general, however, the AP was at a high level. The coefficient of variation (CV) of SOM, TN and AK was 0.5096, 0.4886 and 0.679, respectively, but the CV of AP was more than 100%. The semivariogram of TN and AP was simulated by the model of Spherical, and the semivariogram of SOM and AK, Gaussian. The ratio of nugget to sill of TN, SOM, AK and AP was 0.625, 0.653, 0.733 and 0.999, respectively, indicating that the spatial autocorrelation of soil nutrients was moderately interdependent, respectively.(2) From the areas with higher SOM and TN contents distributing in Chenqiao and Bao town to the vicinity, the values of SOM and TN decreased gradually. Xisha, Dongtan and Beihu were low-vaule areas. The distribution trends of AP and AK were basically complementary.(3) The statistic result of soil nutrient showed that the organic matter and available P of soil surface increased respectively in Chongming, however, the total N and available K, decreased. The increasing of available P was mainly relevant to the application rate of fertilizer, but ignoring the application of N and K resulted in the reduction of soil N and K.(4) The study of soil fertility quality under different land use pattern showed that tillage, land use pattern and the field management were important factors among many influential factors of soil fertility quality. Soil parent material was also regarded as an important factor influencing on the soil fertility.
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