| Based on the materials of soil survey of Chengdu Plain in 1982, sampling scenario in 2002 was devised by grid and stratum sampling approaches. 117 soil samples and 76 underground water samples were sampled and their positions were located by GPS (Global Position System). The regional temporal-spatial variability of soil bulk density, soil organic matter, soil nutrient, nitrate of underground water, soil microbiology and heavy mental were performed by the software ArcGlS8.1 which combined the geographic information system with geostatistics method. Research results were as followed.The soil properties of surface layer in Chengdu Plain in 1982 and 2002 had obviously spatial variability. But their anisotropy and trend effect were various. After 20 years, soil organic matter in 96.4% soil of the regional area increased, and had obviously anisotropy characteristics. Soil total nitrogen in 46.4% soil and available nitrogen in 89.2% soil decreased. Soil available phosphorous increased in 76.4% of the region. Soil available potassium in 76.1% soil increased, but still belonged to deficient level.Nitrate average content of underground water in Chengdu Plain was 4.87 mg L-1, but it in part of region exceeded standard. The contents of heavy mental were not exceeded standard, except that Hg in urban-rural ecotone of Chengdu City and As in tiny area exceeded the standard of soil environmental quality which was ruled by national agricultural bureau. The content of heavy mental and nitrate of underground water had obviously anisotropy and different trend effect. The spatial distribution of nitrate content of underground water gradually decreased from the high value region which was Xinfan Town to outside with strip; most of spatial distribution of heavy mental appeared as strip, a few as lump.The coefficients of variation of soil fungi and bacteria quantities were 1.59 and 1.24, respectively. The random variability of soil fungi was above or amount to 0.90 in spatial variability. but the soil bacteria had obvious structural variability. The quantities of soil fungi were gradually increased from southwest to northeast with strip. The quantities of soil bacteria decreased from the oval center, which was located in the south of Chongzhou and the west of Xinjin, but in the east its trend was decreased firstly, then increased, later decreased again.The soil fertility index values in 70% of the region were 0.50-0.60 in 1982. It distributed in the middle and the west of the area. The region had lowest soil fertility index value in the middle area between Shuangliu and Chongzhou and in the southwest edge of the plain in 2002. Taking the two areas as the center, the index value was gradually increased in circularity. The fertility index values in most parts of the area were above 0.50, it indicated that the whole soil fertility in Chengdu Plain was high.The soil fertility index value in 1982 was lower than that in 2002 as a whole. The area occupied 73.3% of the region of soil fertility index values were increased in the grade map of temporal-spatial variability from 1982 to 2002. This showed that the fertility index values of most of soil in area were gradually increased.The synthesized index values of soil quantity in 2002 were between 0.17 and 0.76. It was divided in five grades. Among the grades, the soil area of grade III was the largest. Following was grade , and thesoil of grade Voccupied the smallest region of the study area. Their percentages were 32.9%, 24.3% and 11.8%, correspondingly. The soil of grade V was mostly distributed in Wenjiang, the southwest of Qionglai and Pujiang, and the east of Longquanyi. The soil quality of Wenjiang and Longquanyi was lower because of the contamination of heavy mental and underground water, but in the southwest of Qionglai and Pujiang that was because of the lower of soil fertility.The balance analysis results of soil nutrient indicated that the fertilization methods of cropland management in Chengdu Plain were firming nitrogen, controlling phosphorus and increasing potassium.
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