Effect of Midterm Drainage on Yield and Fertilizer Nitrogen Use Efficiency on Two High Yielding Varieties of Rice

A field experiment was carried out in kharif season at the Indian Agricultural Research Institute farm, New Delhi, to assess the effect of midterm drainage on yield and fertilizer N use efficiency on rice using ¹⁵N labelled sources on two high yielding varieties of rice (Padma and IR-22). Ammonium sulphate and urea were similar in their effect on grain and straw yield. Continuous flooding was better than midterm drainage treatment. Varietal differences were significant in yield. Percentage utilisation of fertilizer nitrogen was more under continuous flooding than under midterm drainage. It was more in ammonium sulphate than in urea treatment. Varieties differed in their utilisation of fertilizer nitrogen. Utilisation of fertilizer nitrogen was more at primordial initiation stage than at transplanting.