A GIS-based approach to identify the spatial variability of salt affected soil properties and delineation of site-specific management zones: A case study from Egypt

Electrical conductivity of the soil saturated paste extract (ECe), pH and exchangeable sodium percentage (ESP) are most important soil properties to determine and design methods of salt-affected soil reclamation. Surface soil samples from 125 locations in Sahl El-Husseinia, El-Sharkia Governorate, Egypt were taken using hand auger and analyzed for ECe, pH, SAR, ESP and CEC. GPS device was used to record the latitude and longitude of each sampling point. Principal component analysis (PCA) was used to summarize soil properties. ArcGIS software was used to assess spatial distribution pattern of different soil properties. Interpolation mapping to estimate the values of soil properties at un-sampled locations was conducted using ordinary kriging procedure and semi-variogram models were evaluated. Agglomerative hierarchical clustering technique was utilized to define soil management zones. Observed positive strong significant correlation between ECe and other attributes of soil (i.e. ESP, SAR and CEC) with the exception of pH. The PCA resulted that there are two principal components (PCs) explained 80.27% of the total variance of soil properties. The first PC (explained 59.64% of variability) was strongly influenced by soil ECe, SAR, ESP and CEC whereas the second PC showed a more intense relation with pH only. Soil ECe, pH and CEC were pentaspherical, exponential and stable respectively as a best-fit model. Meanwhile, the Spherical model was the best-fit model to SAR and ESP. Based on agglomerative hierarchical clustering, three soil management zones (SMZ) were selected differing significantly with respect to studied soil properties. Calculations for each SMZ concerning gypsum requirements (GR) to reduce ESP to 10 as well as water amount were carried out to reduce ECe to 2 dS m(-1). The amounts of GR are 6.10, 7.05 and 13.37 Mg ha(-1) for SMZ1, SMZ2 and SMZ3, respectively. The amounts of leaching water requirements (LR) for leaching salts from the soil are 2.98, 4.25 and 5.57 m(3) ha(-1) (x1000) for SMZ1, SMZ2 and SMZ3 respectively.