Spatial Variability in Fertility Status of Surface Soils

Knowledge of spatial variability in soil fertility is important for site specific nutrient management. In this study, spatial variability in properties that influence soil fertility such as soil organic carbon (OC), available N, available P O and available K O in surface soils of 154 farmers' fields of Karlawad village in 2 5 2 Navalgund taluk of Dharwad district of Karnataka (India) were quantified and the respective thematic maps were prepared on the basis of ratings of nutrients. Soils sampled (0-20 cm depth) at 154 locations in an area of 1032.15 ha were analyzed for their composition. Arc Map 9.0 with spatial analyst function of Arc GIS software was used to prepare soil fertility maps. Interpolation method employed was spline. Soils were moderately alkaline in reaction with normal Electrical Conductivity (EC). The coefficient of variation (CV) values for soil OC, available N and available P O were 0.35, 0.32 and 0.30 respectively, in the study area and it was lower (0.16) in 2 5 case of available K O. Organic carbon content in the soils was low in majority of the area (683 ha) while it was 2 medium in the remaining area (350 ha). Available nitrogen content was low in 488 ha and medium in 544 ha. Available phosphorus was medium in 622 ha and low in 256 ha and high in the remaining area of 154 ha. The soils in the study area were high in available potassium status. The observed spatial variability in various soil properties that influence soil fertility will help farmers in making crop management decisions.