Computing fertilizer N dose for rice (Oryza sativa) and wheat (Triticum aestivum) for high yield and profit

A long-term field experiment was conducted at university farm, Ludhiana, for 4 years (1988-92) with rice ( Oryza sativa L,) and wheat ( Triticium aestivum L. emend, Fiori & Paol) in rotation with 20 fertilizer treatments, These treatments comprised 5 levels of N, 4 levels of P and 3 levels of K with and without addition of farmyard manure (in addition to 4 control plots) in 4 artificially created fertility strips of a uniform Held, Both rice and wheat responded significantly to N application, The yield response, value ofthe additional produce over preceding N level, profit/ha and rate of marginal response declined sharply with increase in fertilizer N level. Similarly, marginal rate of return also declined sharply with increase in fertilizer N dose, Considering the marginal rate of return of Rs 2.50 or more for each rupee spent on fertilizer N as optimum, fertilizer N dose was worked out to be 125 and 100 kg N/ha in rice and 125 kg N/ha in wheat without and with farmyard manure respectively. Addition of farmyard manure raised the production potential of both rice and wheat and saved about 25 kg N/ha in rice.