Long term effect of integrated nutrient management on yield and economics of rice (Oryza sativaL.)-wheat (Triticum aestivumL.) system in north-western Himalaya

The present investigation was carried out to study the integrated effect of nutrient management on rice and wheat yield and its economics in an on-going long term fertilizer experiment initiated during kharif 1991 at CSK Himachal Pradesh Krishi Vishvavidyalaya, Palampur. Eight treatments comprising control, 100% NPK (inorganic) and conjoint use of 50 and 75% NPK with 50 and 25% N substitution either through FYM, wheat straw or green manure Sesbania aculeata to rice (June-October) followed by 100 and 75% NPK through inorganics to wheat (November-May), respectively, were imposed since the inception of the experiment. Grain and straw yields of both the crops were recorded after 20th and 21st cropping cycles (2010–11 and 2011–12). The omission of chemical fertilizers and organics for last 20 years (control) resulted in significantly lower yield in comparison to rest of the treatments. Continuous substitution of 50% N through green manure with 50% NPK produced maximum rice grain (7.37 t/ha) and straw (6.21 t/ha) yield which was 16.8 and 14.8% higher over 100% NPK alone. In case of wheat, highest grain yield (3.64 t/ha) was recorded in treatment where 50% N was substituted through FYM to rice crop every year. The data further revealed that application of (i) 50% NPK+50% N through FYM to rice followed by 100% NPK to wheat, (ii) 100% NPK to both the crops and (iii) 50% NPK+50% N through green manure to rice followed by 100% NPK to wheat gave significantly higher net returns (193, 170 and 163%, respectively) over control. The highest benefit: cost (B: C) ratio of 1.40 was recorded in treatment where 100% NPK was applied to both the crops followed by 1.22 in treatment where 50% NPK+50% N through FYM to rice followed by 100% NPK to wheat was applied.