Spatial variability of soil available N，P and K and influencing factors

Studies on the spatial variability characteristic of soil available nutrient contents in county scale could provide a guidance for improving agricultural planning. Geostatistics combined with GIS were used for the analysis of the spatial variability characteristics of soil available nitrogen (AN), available phosphorus (AP) and available potassium (AK) and their influencing factors in Shuangliu county in Sichuan province. The results indicated: 1) AN and AK contents were strongly and spatially dependent, the range of spatial dependence was 77840 m and 75482 m. Structural factors were the main factors which affected the spatial variability of AN and AK contents. AP content had moderate spatial dependence, the range of spatial dependence was 25590 m, and the spatial variability was caused by structural factors and random factors. 2) AN content was decreased from north to south, AP contents was decresed from northeast to southwest and southeast to northwest, whereas AK contents was decreased from southeast to northwest. 3) AN content was significantly different among different soil types or geography; AP content was significantly different among different soil parent materials whereas significantly different among different geomorphologic conditions; AK content was significantly different among different soil parent materials. The fertilizer application rate at the regions with high soil available N，P and K contents were obviously higher than regions with low soil available nutrient contents.