Abstract

                                Delineation of available macronutrients was carried out by randomly collecting geo referenced surface (0-0.15m) soil samples representing different soil units as per the soil map prepared on 1:50,000 scale from 598 sites in Theni district, Tamil Nadu using Global Positioning System (GPS). The soil samples were analysed for available macronutrients. The available N status ranged from 129 to 322 kg ha -1 while the available P and K status varied from 7.34 to 65 kg ha - 1 and 122 to 697 kg ha-1 respectively. Analytical results and the GPS data were used for the preparation of thematic map showing spatial distribution of macronutrients status block wise in the district. Locations of soil sampling sites of Theni district were marked on base map on 1:50,000 scale prepared from State Revenue Maps and digitized using Arc-info GIS. The delineation study clearly indicated that the available N was found to be low in 73.71 percent of soils of Theni district while phosphorus is in medium status. Nearly 70 per cent of the surface soil of Theni district was high in available K status.

Key words : Available Nitrogen, Phosphorus, Potassium, GPS, GIS, Thematic maps.