Experimental research on spatial variability of soil water at large-field scale

In order to characterize the spatial variability of soil water content at large field-scale in a semi-arid zone, this paper analysed data of 6 layers in depth based on 105 profiles in the Qingshuihe Plain with classical statistics and geostatistic methods. Prominent differences exist in vertical distribution of soil water between rainfed farmland and irrigation field. For the same confidence level and precision, the reasonable sampling number of soil water content of the rainfed farmland is obviously much higher than that of irrigation field and sampling number of the deep layers is higher than that of the shallow layers at the same depth. Spatial relativity of regional soil water content is medium to weak, and high value area of soil water content is coincident with the irrigation area. The results show that in the semi-arid zone, irrigation is not a key factor influencing the spatial variability of soil water. The spatial variability of soil water of irrigation field is weaker than that of rainfed farmland, and the spatial variability of the shallow layers is weaker than that of the deep layers. The spatial distribution of soil water content is consistent with the farmland type.