Efficacy of slow release nitrogen-fertilizers to rice (Oryza sativa) and their residual effect on wheat (Triticum aestivum)

A field experiment was conducted during 1989-91 on sandy clay loam soil at Ranchi to study the efficiency of forms of urea, viz, prilled (PU), lac-coa ted (LCU), rock phosphate-coated (RCU), karanj cake-coated (KCU) and neem c ake-coated (NCU) at varying N rates (0, 40, 80, 120 kg/ha) on the productiv ity of rice (Oryza sativa L.) and their residual effect on succeeding wheat ( Triticum aestivum L. emend. Fiori & Paol.). The LCU, NCU, and KCU gave 2 4, 14.2 and 12.7% more grain yield of rice respectively than PU. Each incre mental N levels recorded higher grain yield over its preceeding levels. How ever, nitrogen-use efficiency decreased with increasing N level. Applicatio n of LCU, NCU and KCU favourably affected soil-available N after rice which consequently exhibited more residual effect on the productivity of succeed ing wheat. Rice fertilized with 120 kg N/ha also recorded maximum grain yie ld of succeeding wheat (23.1 q/ha).