Dynamics of Actual Evapotranspiration of Tomato under Different Irrigation Regimes and Nitrogen Levels in New Alluvial Zone of West Bengal

A field experiment was conducted on a sandy loam soil (Typic Haplustept) during the rabi season of the years 2002–03 and 2003–04, to study the effect of irrigation regimes and nitrogen fertilization on the dynamics of actual evapotranspiration (A₀) of hybrid tomato after determining the various components of field water balance. Three irrigation regimes were maintained by scheduling irrigation at 1.2 (I₁), 1.0 (I₂) and 0.8 (I₃) IW/CPE ratio with 5 cm of irrigation water in combination with three nitrogen levels applied @ 0 (N₀), 80 (N₂) and 160 (N₄) kg ha⁻¹. In both the years, wetter moisture regimes and addition of nitrogen helped the crop to deplete more moisture from the soil profile to meet the evaporative demand. The magnitude of either capillary flux or deep drainage within the rhizosphere during the study period was very less due to presence of deeper water table (3.5 m). In general, periodic evapotranspiration rates under all the irrigation regimes and nitrogen levels were low at initial stages of crop growth, which gradually increased with time and attained maximum during the fruit formation stage (65–75 DAS) and then gradually decreased. However, evapotranspiration rates were always higher under wetter moisture regimes and increasing levels of nitrogen up to 80 kg ha⁻¹. The I₁ irrigation regime produced 12.67 and 24.37% more crop water use than I₂ and I₃ regimes while N₄ nitrogen treatment enhanced only 2.85 and 7.22% over N₂ and N₀ treatments, respectively. Average yield and water use efficiency of tomato also significantly responded to both the irrigation regimes and addition of nitrogen. Wetter moisture regimes (I₁) increased the yield by 12.39 and 26.89% over drier moisture regimes of I₂ and I₃, respectively. Similarly application of 160 kg ha⁻¹ (N₄) improved the yield by 10.25 and 251% over the plot that had received 80 kg ha⁻¹ and no nitrogen.