Mapping of soil test-based spatial fertilizer recommendations for paddy and maize using GIS, GPS and STCR approaches in a micro-watershed of Karnataka, India

A case study was undertaken at the Honnavalli microwatershed of Hassan district, Karnataka, India, to prepare digital maps for site-specific fertilizer recommendations for the major crops (paddy and maize) using STCR approach. The map shows that the recommended dose of N fertilizer for paddy is 148, 111, 82, 54, 26, -8, -67 and -108 kg ha-1 for the soil available N status <200, 200-250, 250-280, 280-325, 325-375, 375-425, 425-500 and >500 kg respectively. Similarly, for maize it is 290, 286, 283, 281, 279, 276, 268 and 259 kg ha-1 for <250, 250-275, 275-300, 300-325, 325-350, 350-400, 400-500 and >500 kg ha-1 respectively. Therefore, the study has implications on reducing consumption of fertilizers (24-45% for N; 12-15% for P and 8-32% for K), thereby reducing the cost of cultivation besides achieving higher nutrient use efficiency.