Optimization of Fertilizers at Varying Soil Test Values and Crop Seasonal Rainfall for Fingermillet under Semi-Arid Alfisols

: Based on a sudy conducted on finger millet at Bangalore during 1984 to 2006, an attempt is made to develop soil test and crop seasonal rainfall based optimum fertilizer doses for sustainable yield under semi-arid alfisols. The effects of soil nutrients on finger millet productivity and its sustainability have been modeled and a suitable fertilizer treatment for enhancing soil fertility of nutrients has been identified. The models of N, P and K nutrients were calibrated separately for < 500, 500–750, 750–1000 and 1000–1250 mm rainfall situations. The models gave a predictability in the range of 0.42 to 0.78 under FYM block and 0.21 to 0.83 under maize residue block. Based on the models, soil test based optimum fertilizer doses were derived for each rainfall situation. The optimum doses ranged from 22to 32 kg ha⁻¹ of N; 10to 49 kg ha⁻¹ of P and 12to 22 kg ha⁻¹ of K under crop seasonal rainfall of 750–1000 mm for attaining a sustainable grain yield of 3086 kg ha⁻¹ under FYM block. Similarly they ranged from 0 to 70 kg ha⁻¹ of N, -0 to 97 kg ha⁻¹ of P and 3 to 33 kg ha⁻¹ of K for attaining a yield of 4305 kg ha⁻¹ under maize residue block.