KR Gade, G Manjulatha, N Vikram
Soil fertility heterogeneity at micro-spatial scales remains a major constraint to efficient nutrient management in intensively cultivated systems. The present study assessed the spatial distribution and status of soil macro- and micronutrients at the Agricultural Research Station using geo-referenced soil analysis. A total of 43 surface soil samples (0–15 cm) were collected and analysed for physicochemical properties and available nutrients. Spatial interpolation was performed using inverse distance weighting (IDW) in a GIS environment to delineate nutrient variability across the study area. The soils were slightly acidic to neutral (pH 5.41–7.65), non-saline, and moderately supplied with organic carbon. Available nitrogen was predominantly deficient, whereas phosphorus and potassium were mostly in medium to high categories, indicating nutrient imbalance. Sulphur was uniformly sufficient, while boron was deficient throughout the study area and iron deficiency was observed in a considerable portion of the farm. Correlation analysis revealed that soil pH exerted a strong influence on micronutrient availability, showing significant negative relationships with Fe, Mn, and Cu. Positive associations among these micronutrients suggested common geochemical controls. Principal Component Analysis (PCA) indicated that the first two components explained 43.5% of the total variance, with Fe, Mn, Cu, and available phosphorus contributing substantially to soil variability. The integration of geo-referenced sampling, multivariate analysis, and GIS-based spatial mapping enabled precise identification of nutrient-deficient zones. The study highlights the need for site-specific nutrient management, particularly targeted nitrogen and boron fertilization, to improve nutrient use efficiency, sustain soil health, and enhance crop productivity under semi-arid conditions.