Response of Indian Mustard (Brassica juncea L.) to Nitrogen and Phosphorus Application in Soils of Variable Texture and Fertility

Field experiments were conduced with Indian mustard to study its response to N and P on cultivators' fields over a period of 4 years on 20 and 17 sites, differing in soil fertility and texture, respectively. The crop responded significantly to applied N in all the soils and to applied P in low P soils. For getting higher profits on N use, relatively higher N doses needed to be applied in fine textured soils testing organic carbon> 0.20 per cent. For economic returns on P use, more P should be applied in low P soils having <0.20 per cent organic carbon. For better prediction of N responses, both organic carbon and KMnO₄-N should be taken into account. Similarly, for predicting P responses both organic carbon and Olsen's extractable P should be considered. The values of critical levels of KMnO₄-N and Ofsen's extractable P below which crop will definitely respond to fertilizer application were 140 and 12 kg ha⁻¹ respectively.