Abstract

                                Knowledge on the soil variability of research stations is imperative for the assessment of land capability for specific land use and for the correlation of experimental data generated in various research trials. A study was undertaken in Coconut Research Station, Aliyar Nagar to characterize the spatial variability of available macronutrients (nitrogen (N), phosphorus (P) and potassium (K)) and to compute their respective nutrient indices. Two hundred and fifty eight geo - referenced soil samples were collected from the surface (0-15 cm) and subsurface (15- 30 cm) layers of A, B and C blocks of the farm. The farm soil is predominantly sandy textured belonging to the taxonomic class Typic / Fluventic Ustropept. KMnO4 – N, Olsen P and 1NNH4OAc K were estimated adopting the standard procedures. GIS aided fertility maps were prepared employing Arc-GIS software and nutrient indices were computed. Acute deficiencies of nitrogen and moderate deficiencies of phosphorus and potassium were observed in the soils. Sandy texture of the soil, intensive irrigation systems, paucity of organic matter, low base exchange status and kaolinitic clay mineral with poor potassium binding sites are the potential causes for nutrient deficiencies. Enhancing the organic matter load through residue recycling, split application of N and K fertilizers and water saving irrigation systems can reverse the above effect.

Key words : Fertility mapping, GIS, Nutrient index, Spatial variability.