Effect of varying fertilization on yield of rice (Oryza sativa)-wheat (Triticum, aestivum) system and soil fertility status

A field experiment was conducted at Almora during 1994-99 to work out the fertilizer requirement of rice (Oryza saliva L.)-wheat (Triticum aestivum L. emend. Fiori & Paol.) system under irrigated conditions. Rice with recommended NPK (P as diammonium phosphate) and wheat with recommended NPK (P as single superphosphate) gave the highest grain yield during all the years. Application of only nitrogen was more detrimental to wheat than rice. Skipping P application drastically reduced the grain yield of wheat in the fourth year, but it did not hold true in case of rice. In the control treatment, rice gave almost 3 times more grain yield (2.67 tonnes/ha) than wheat (0.97 tonne/ha), but both had almost comparable yield level in the highest yield-producing treatments, i e NPK, P as diammonium phosphate in rice (4.71 tonnes/ha) and NPK, P as single superphosphate in wheat (4.92 tonnes/ha). Reducing the recommended fertilizer dose to half along with sunnhemp (Crotalaria juncea L.) green-manuring recorded at par yield of rice with the recommended NPK. None of inorganic fertilizer treatments was capable of maintaining soil fertility except green-manuring with 100 or 50% of NPK.