Spatial characteristics of soil nutrients in the Loess Plateau watershed and its correlation with terrain factors

【Objective】This study investigated the relationship between topographic factors and spatial characteristics of soil nutrients in the Loess Plateau watershed,in order to improve the efficient use of land resources and accurate nutrient management.【Method】Hongyan River watershed in Bin County,Shaanxi province,was selected and a total of 121 soil samples were collected with the use of GPS in 2011.SOM,available N,available P and available K contents were measured.Semivariogram theoretical models and their parameters for soil nutrients in the surface layer were analyzed using geostatistical method.Furthermore,spatial distribution of soil nutrients was plotted using Kriging interpolation,and the correlations between terrain factors such as elevation,gradient,slope direction,slope and soil nutrient contents were statistical analyzed.At last,the interpolation results were verified.【Result】Soil available N showed weak spatial variability while SOM,available P and available K showed strong spatial variability.The spatial distribution of all soil nutrients were spotted,without zonal trend.Generally,all soil nutrients were negatively correlatedwith elevation and gradient,and positively correlated with slope aspect.The correlation with slope shape was not significant.【Conclusion】Random factors played a dominating role in spatial variability of available N,and the variation range was short.The spatial variability of SOM,available P and available K were mainly caused by structural factors,and the variation range was long.In addition,Elevation,gradient and slope aspect showed significant impacts on contents and distribution of soil nutrients.