Variability and similarity of soils in Rajkot district, Gujarat

The physical and chemical characteristics of eleven soil series identified during reconnaissance survey of Rajkot district in Gujarat state were used to measure the soil variability in five geomorphologically defined survey units and then to assess their similarities for subsequent identification of soil subgroups. The variability of individual soil properties as defined by coefficient of variation was found to be varying widely in soils occurring in upper piedmonts and in flood plains. The marked differences in soil properties in geomorphic units indicated that the level of sampling intensity is inadequate to estimate mean soil conditions in different survey units. The estimated similarity index values were used to construct dendogram for identifying three distinct soil groups relating closely with the Soil Taxonomy. High degree of similarity was noticed in soil subgroups of Vertisols occurring in lower piedmonts and flood plains as compared to soils occurring in higher topographic units. Examination of soil groups indicated that clay, electrolyte concentration, calcium carbonate and exchangeable sodium contents are considered as diagnostic properties for classification. Results suggested that these soil properties which vary widely may be considered and tested in land evaluation programmes.