Spatial variability of topsoil chemical properties

Soil properties vary spatially and temporally because of soil formation processes, land use pattern, fertilizations etc. Geo-statistics, remote sensing and GIS offer some of the best tools and techniques to capture the spatial variability of soil properties. Study area chosen for the investigation is situated in the coastal zone, covering a part of Dakshina Kannada and Udupi Districts, Karnataka. Study area predominantly consists of sandy, loamy sand and gravelly elay soils. Harvested agricultural paddy fields were identified as soil sampling locations. A total of 260 soil samples were collected from top 0-20 cm of soil surface and were air dried. Measurement of topsoil chemical properties such as Organic Matter (OM), pH, Electrical Conductivity (EC), Nitrogen (N), Phosphorus (P), Potassium (K), Calcium (Ca) and Iron Oxide (Fe2O3) were carried out as per Indian Standard Codes. Descriptive statistics were computed, correlation between the soil properties was explored and also soil properties were interpolated and mapped using IDW interpolation method. Soil properties have very large variability. In this region topography and vegetation is homogeneous, and no erosion activity is observed. So the only reason for the high variability of soil properties is agricultural practices. Correlation among soil properties is not consistent. There is no significant influence of soil type on soil properties range. Restoration of small scale farmers is important in food security point of view.