Digital soil fertility mapping of a Pashupathihal-2 micro-watershed in Kundgol taluk, Karnataka state through GIS

The study evaluates the spatial variability of soil fertility in the Pashupathihal-2 micro-watershed (428.8 ha) using remote sensing-assisted digital soil mapping and GIS-based geostatistical techniques to support precision nutrient management. The study revealed considerable spatial variability in soil physicochemical and nutrient characteristics, indicating heterogeneous soil health and fertility status. The soils were primarily slightly to strongly alkaline, with pH values ranging from 8 to 9.16 (mean 8.66). They exhibited non-saline electrical conductivity levels (mean 0.57 dS/m), typical of the black clay vertisols found in the region. Organic carbon levels varied from 0.15 to 0.87 %, with 79.61 % of the area falling into the medium organic carbon category, reflecting moderate organic matter content. Nitrogen levels were predominantly low (mean 140.83 kg/ha), with nearly 30 % of the area classified as very low, suggesting potential nutrient depletion possibly linked to reduced organic matter. Phosphorus availability (mean 27.92 kg/ha) remained within a moderate range, although its uneven distribution suggests the need for site-specific fertilization. Potassium content was generally sufficient (mean 475.32 kg/ha) due to inherent soil properties but showed spatial discrepancies that may affect nutrient balance. Micronutrient assessment revealed a critical deficiency in iron, with 80.56 % of the area below the sufficiency threshold (<4.5 ppm), while manganese, copper and zinc were reported in adequate quantities throughout the watershed. These findings highlight the contribution of geospatial tools in identifying soil constraints, facilitating precision nutrient management and supporting sustainable agricultural practices through informed land-use planning.