Spatial Variability Analysis on Soil Nutrients in Semi-Arid Agro-Pastoral Transition Area—A Case Study in EjinHolo Banner,Inner Mongolia

Ejin Holo Banner in the west of the Inner Mongolia Autonomous Region,China,is a typical semi-arid agro-pastoral transition area.In this paper,a case study on comparing different methods of interpolation and finding the best prediction map were carried on in Ejin Holo Banner based on the application of GIS.Then the spatial variation of soil nutrients was analyzed because it was the foundation of planning agricultural position and environmental reconstruction.Comparing the prediction values with actual values, Inverse Distance Weighted for soil organic matter(O.M),exponential model of Ordinary Kriging for total nitrogen(Total.N) and Gauss model of Ordinary Kriging for soil available K(Avail K) was respectively the best method for their interpolations.Geo-statistical analysis showed that the spatial autocorrelation ranges of O.M,Total.N and Avail.K were 11853m,8932.2m and 732.99m.And the ratio of nugget and sill indicated that the spatial autocorrelation of Total.N and Avail.K was medium.However,the spatial autocorrelation of O.M was weak.The prediction map of O.M showed that its content was low(10g/kg) in 90% of areas,and the areas with relative high value were scattered,the cause of which was related with peculiar topography.The distributions of total nitrogen and soil organic matter were analogical.The content of Total.N was low(0.75g/kg) in 70% areas,but the content of Avail.K was universal medium(102.04-103.31mg/kg).In three subregions,the order on the situation of soil nutrient was Wushen Lowland subregion Mu Us Sandland subregion Loess Hill subregion.