Spatial distribution of available micronutrients in agricultural soils using GIS approach

Abstract:

Hidden hunger in hill soils deficiencies of zinc, boron, and other micronutrients that are invisible until crop yields fall remains a poorly mapped problem across much of the Nepalese Himalayan region. This research assessed the spatial distribution of plant-available zinc (Zn), copper (Cu), iron (Fe), manganese (Mn), and boron (B) in agricultural soils of Kaski district, Nepal, using a Geographic Information System framework. A total of 120 geo-referenced surface soil samples (0-20 cm depth) were collected across four topographic zones valley floor, mid-slope, upland, and ridge top during the pre-Kharif season of 2023. Samples were analysed for DTPA-extractable Zn, Cu, Fe, and Mn, and hot-water-soluble B. Inverse distance weighting interpolation in ArcGIS 10.8 was used to generate thematic maps for each nutrient. Boron showed the widest deficiency (56.8 % of samples below the critical limit), followed by Zn (42.3 %). Micronutrient concentrations declined consistently from valley floor to ridge top, reflecting the combined influence of organic matter content, soil pH, and erosion intensity. The resulting maps offer a practical tool for site-specific fertiliser recommendations in Nepal's hill agriculture.