National Bureau of Soil Survey and Land Use Planning, Regional Centre, Jorhat, 785 004, Assam
*Corresponding author (Email: reza_ssac@yahoo.co.in
Present address 1National Bureau of Soil Survey and Land Use Planning, Nagpur, 440 030, Maharashtra
Online published on 6 September, 2012.
The objective of this study was to determine, the degree of spatial variability of pH, organic carbon (OC), available nitrogen (AN) and available potassium (AK) of Goalpara district of Assam. A total of 1397 soil samples from a depth of 0–25 cm at an approximate interval of 1 km were collected over the entire district. Data were analyzed both statistically and geostatistically on the basis of semivariogram. Soil properties showed large variability with greatest variation observed in AK (42%) whereas the smallest variation was in pH (16%). The semivariogram for all soil properties were best fitted by exponential models and showed a highest (3.8 km) range for pH and lowest (2.0 km) for AN. The nugget/sill ratio indicates a strong dependence for pH (19%), moderate spatial dependence for OC (60%) and a weak spatial dependence for other soil properties. Evaluation of spatial maps indicated that except for AN, kriging could successfully interpolate other soil properties. Soil pH was significantly negatively correlated with OC (r = -0.434**) and AN (r = -0.228**). A significant positive relationship was observed between OC with AN (r = 0.498**) and AK (r = 0.119**).
Spatial variability, kriging, semivariogram, accuracy assessment, soil properties, Brahmaputra plains
