Effect of water regimes and nitrogen levels on rice crop performance and nitrogen uptake

A field trial was carried out to study the effect of different water regimes and nitrogen levels on growth pattern, economics, nitrogen uptake and water saving in rice (Oryza sativa L.) in a silty clay loam soil (Aquic hapludoll) associated with shallow water tables at Horiculture Research Center, Patharchatta located in the campus of G.B.P.U.A. & T, Pantnagar, Uttarakhand. A split plot design with four replications was used with three water regimes (W_cf continuous flooding of 5cm; W_fs= flooding to saturation; W^rf Rainfed) as main plots treatments and four nitrogen levels (N₀=0kgN ha⁻¹;N₆₀=60kgN ha⁻¹; N₁₂₀=120kg N ha⁻¹; N₁₈₀=180kgN ha⁻¹) as subplots treatments. The water table fluctuated between 0.0m-0.35m depths from the surface during rice growing season. The two years data revealed that the rainfed treatment receiving 180kgN ha⁻¹ had better crop growth and nitrogen uptake as compared to the other treatments. Higher tillers no., plant height, dry matter production, leaf area index, panicle m⁻² were recorded under rainfed condition receiving 180kgN ha⁻¹. Grain yield ofrice across water regimes was significantly higher (61.22q ha⁻¹) in rainfed treatment followed by flooding to saturation (57.95q ha⁻¹) and continuous flooding (57.25q ha⁻¹). Similarly, highest grain yield of 70.60q ha⁻¹ was attained with an application of 180 kg N ha⁻¹ The lowest yield (44.12q ha⁻¹) was recorded in the control plot. Rainfed treatment was found to be the most economic with BC ratio 2.05 comparison to flooding to saturation (W_fs) and continuous flooding (We£). Among the nitrogen treatment the highest B: C ratio was observed in the N₁₈₀ kg ha⁻¹ (2.17) followed by N₁₂₀, N₆akg ha⁻¹. The lowest B: C ratio was observed in the N₀kg ha⁻¹ (1.28). The total N uptake was 14.3%, 19.6% lower at active tillering and 6.5%, 10% lower at maturity stages in W_fs and W_cf treatment respectively than the rainfed treatment. The application of 180KgN ha⁻¹ improved the N uptake followed by N₁₂₀ N₆₀ and control. The experimental findings of present study indicated that in the shallow water table conditions higher yield can be obtained under rainfed conditions, thereby, increasing the water use as well as nitrogenuse efficiency in rice.