Study On Spatial Variability And Simulation For Soil Potassium In Chengdu Plain

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 soils that were sampled and their positions were located by GPS (Global Position System) were tested for soil tatal potassium (STK) and soil available potassium (SAK) and other soil properties. The STK and SAK content of 117 soils was analysised by geographic information system software (ArcGIS-version 9.0) and simulated by Monte Carlo Method. Present status STK and SAK was appraised and useful control measures of STK and SAK was advanced. The main results were as follows.The average content of STK in 2002 was between 13.83g kg^-1 and 21.31g kg^-1, which was lower than that in 1982, discrepancy 7.48g kg^-1. The mean content of STK in highest value region was 21.31 g kg^-1 which diffused to east, south and west, including all the area of Pixian county, Wenjiang county and the southeast of Dujiangyan county, the main city zone of Chengdu and the west of Pengzhou county, the north of Shuangliu county. The area was near double as 1982. The mean content of STK in lowest value region was 13.83 g kg^-1 whose distributing area did not changed.The average content of SAK in 2002 was between 47mg kg^-1 and 171mg kg^-1, discrepancy 124 mg kg^-1. The spatial distribution characteristics of SAK content in 2002 apeared as reducing trend from southeast to middle part of the study aera as a whole. The highest value region (15 8²13mg kg^-1, grade II) which appeared as strip station mainly distributed the straitnesss of the southwest of Longquanyi county, and decreasing to the middle of the study area. The lowest value region (24⁵8mg kg^-1, grade V) had been separated into five parts, the area decreased obviously, which had reduced tenth than that of 1982, but the average content had increased a few than that of 1982. The distribution range of the lowest value region was diffusing to the northwest and southwest, contains of the south of Pixian county, the west of Wenjiang county, the south of Qionglai county and Shuangliu county, especially the area in the west and south of Shuangliu county was the largest.Parent material, components of soil particle, soil organic matter and landuse type had impact on the content of soil potassium to some extent. According to the statistical results, the content of soil total potassium in 2002 developed from parent material follows like this: Old alluvium > Grey alluvium > Grey-brown alluvium > Chengdu clay. The content of soil available potassium had the relationship of Chengdu clay > Grey alluvium > Old alluvium > Grey alluvium. There was a obvious positive...