Spatial Distribution Characteristics of Available Microelement Contents in Oasis Cropland Soils of Arid Areas

The method of geostatistics combined with GIS was applied to study the spatial variability characteristics,distribution laws and influencing factors of available Fe,Cu,Zn,Mn,Ni and Co contents in farmland topsoils from the Shandan and Minle Counties of Zhangye City,Gansu Province.The results showed that the soils relatively lacked available Fe and Zn concentrations,and the six microelements all belonged to moderate variability level.Better theoretical semivariogram models of available microelements were the spherical model for Cu,Zn and Ni,the exponential model for Fe and Co,and the Gaussian model for Mn.Available concentrations of Fe,Cu,Mn,Ni and Co had strong spatial correlations.The contents of available Zn had a moderate spatial correlation.The variation range of the six microelements available contents followed the order Fe Ni Zn Co Mn Cu.The contents of available Fe and Ni presented clear continuous zonal distribution,and a decreasing trend was found from south to north.The distributions of Mn and Co presented an island shape.The contents of available Fe and Zn were moderate or poor in the soils,while the contents of available Cu,Mn and Ni were moderate or rich in the soils.Moreover,the contents of available microelements,except for Cu,were mostly influenced by organic matter in the study area.