Geo-spatial analysis for horizontal and vertical variability of bulk density, particle-size distribution and soil moisture content in Tripura, Northeastern India

The bulk density (BD), particle-size distribution and soil moisture content (SMC) are important properties that govern the physical and mechanical behaviours of the soil and also provide crucial information on the pedogenesis of soils. A total of 153 soil profiles were randomly selected and studied from part of Sepahijala district, Tripura, Northeastern India. The horizon-wise soil property data were converted to fixed-depth data for 0–20, 20–40, 40–60, 60 − 80 and 80–100 cm of soil depth. The result showed that the mean values of BD 1.51, 1.60, 1.59, 1.55 and 1.55 Mg m−3; sand 37.7, 38.1, 36.9, 36.0, and 37.3%; silt 29.1, 26.8, 28.0, 28.3 and 27.2%; clay 33.2, 35.1, 35.1, 35.7 and 35.5%; and SMC 21.4, 20.2, 21.2, 21.3 and 19.4% in the 0 − 20, 20 − 40, 40 − 60, 60 − 80 and 80 − 100 cm depths, respectively. The values of CV for soil variables ranged from 9.4 to 70.0% for all the depths. The CVs indicated that BD had lowest variability, while sand and SMC showed high variability in all the depths. Stein, circular, spherical, exponential and Gaussian models were found to be the best fit for semivariograms of different physical properties for different soil depths. The nugget to sill ratios of the empirical semivariograms for all the layers of BD, clay and SMC indicated moderate spatial dependence, except the 80 − 100 cm of BD and clay and 20 − 40 and 60 − 80 cm of SMC, which showed strong spatial dependence. Soil physical properties exhibited different distribution pattern. Spatial distribution maps of BD showed that except surface layer, the BD is lower in the southern part of the study area, and decreasing towards the northern parts in all the depths may be due to higher clay content in this region. The spatial distribution of SMC closely followed the distribution pattern of sand and clay contents. The developed maps prepared in this study may be useful to farmers, planners and decision-makers for improving soil–water management.