Spatial variability of soil total nitrogen,available phosphorus and available potassium in Huanghuadianzi watershed

The spatial autocorrelation,semi-variograms and Kriging interpolation were used to study the spatial variations of total nitrogen,available phosphorus and available potassium in Huanghuadianzi watershed in Aohan Chifeng,Inner Mongolia based on the field sampling. The results showed that total nitrogen,available phosphorus and available potassium were in island distribution on the whole. Total nitrogen and available phosphorus showed a scattered fertile islandsdistribution,while available potassium showed an obvious island distribution. The spatial autocorrelation of nutrients increased with the decrease of lag distance. There were positively and negatively correlated regions,corresponding to the spatial clustering and spatial isolation,respectively. The C0/( C + C0) value of available phosphorus was 17. 21%,belonging to a strong spatial correlation. Such values for total nitrogen and available potassium were 27. 03% and 44. 99%,respectively,belonging to a moderate spatial correlation. Both spatial autocorrelation distance and range were in order of total nitrogen available phosphorus available potassium. The nutrient contents under different land-use types were in order of cropland forestland grassland. Human activity was the main factor influencing the spatial variability of nutrients in the study area.