Assessment of spatial variability in fertility status and nutrient recommendation in alanatha Cluster Villages, Ramanagara District, Karnataka using GIS

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 nitrogen (N), available phosphorus (P), available potassium (K) and secondary and micronutrients in surface soils (0–30 cm depth) of 67 farmers’ fields of Alanatha Cluster Villages, Kanakapura Taluk, Ramanagara District, Karnataka was quantified and the respective thematic maps were prepared on the basis of ratings of nutrients. Arc map with spatial analyst function of Arc GIS software was used to prepare soil fertility maps. Soils were strongly acidic to slightly acidic in reaction with normal electrical conductivity (EC). Soil OC content was low to high, available N low to medium and available P and available K low to high. The soil of sampled area were found to be 100 per cent sufficient in exchangeable calcium, 97 per cent area was found to be sufficient in exchangeable magnesium. Available sulphur status was found to be low to high. The entire area was found to be sufficient in available manganese and copper, 86.5 per cent area was sufficient in zinc and 85.0 per cent area was sufficient in iron in surface soils. The observed spatial variability in soil properties that influence soil fertility was used for deciding nutrient application to finger millet and groundnut. Thus, providing balanced nutrients to crops based on soil of fertility status resulted in enhanced crop productivity and net returns in both groundnut and finger millet cropping systems.