Spatial variability and mapping of selected soil properties in Kaligaudanahalli Microwatershed, Gundlupet Taluk, Chamarajanagar District, under hot semi arid agrosubregion of Central Karnataka Plateau, India

Abstract

The soil attributes of spatially structured data were often measured in Central plateau, of Karnataka, but often poorly defined spatial variability of soil attributes important for land management under hot semiarid agroecological environment. The Kaligaudanahalli microwatershed (612 ha) divided into 250 m × 250 m square grids using ArcGIS and collected surface soils (0–15 cm) at 89 locations. The results of cluster analysis with average linkage method revealed four soil typologies viz., slightly alkaline, sandy clay loam texture showing high coefficient of variation for all soil variables in cluster-I, but neutral, sandy clay loam with high variability for DTPA-extractable Cu in cluster-II, moderately alkaline sandy clay loam to clay texture with high variability for EC, OC, available K2O, B and Cu for cluster-III and IV. The study concluded that the measured soil properties in regular gird sampling at given scale were enough to capture spatial dependence using ordinary and cokriging techniques and in deriving thematic maps for efficient soil management strategies at watershed level. The results of spatial dependence of each soil property, using ordinary kriging showed that there is strong spatial dependence of pH, EC, K2O, B, Cu, Fe and Mn with nugget-to-sill ratio [(C0/C0 + C)] less than 0.25 showing strong spatial distribution where DTPA-extractable Zn had a nugget/sill more than 0.75, displaying a weak spatial autocorrelation. The results showed that cokriging is the best fit and strongly correlated with EC, P2O5, K2O, Fe and Mn using pH as ancillary variable over ordinary kriging to derive thematic maps.