Spatial Variability of Some Soil Characteristics in Lands of Zanjan University

 Assessing the spatial variability trend of various soil properties is a helpful procedure to access to the efficient site-specific management of this ecosystem vital component. Aimed to investigate the spatial soil variability in lands of Zanjan University, 48 topsoil (0-25) samples were collected based on a regular grid of 250 meter. Soil samples were analyzed for some physical properties, including bulk density, available water capacity, saturated hydraulic conductivity, mean weight diameter and clay, sand, organic carbon and equivalent calcium carbonate percentage. Identifying the spatial structure of selected properties, ordinary kriging was used to estimate the values of soil properties in un-sampled locations and continuous maps were prepared. The results showed that saturated hydraulic conductivity (43.28%) and bulk density (5.53%) had the maximum and minimum coefficients of variations, respectively. The spherical model was performed well to describe the spatial structure of organic carbon and carbonate calcium equivalent; whereas exponential model showed the best fit to the remained soil properties. Saturated hydraulic conductivity showed a strong correlation class; whereas spatial structure of other studied properties was moderately correlated. Interpolated maps revealed that increasing clay percentage from the south to the north of study area led to the decreased contents of saturated hydraulic conductivity and increased values of available water capacity. This observation indicated that considering soil youthfulness and less-developed soil structure, most of the soil physical properties are mainly influenced by soil texture. It is also observed that cultivated crops in the south of studied area and apple trees in the north, resulted in the soil organic carbon to be increased to more than 1%, in turn, led to the significant increase in mean weight diameter of soil aggregates in these areas.