Response of young Shahi litchi trees to drip irrigation

Young 2½ years old litchi trees (cv. Shahi) were subjected to 4 drip irrigation treatments, viz. irrigation to replenish 25, 50, 75 and 100% evapotranspiration (ET) losses for two consecutive years (2002–03). The control trees did not receive any supplemental irrigation. Irrigation with a pre-set volume of water was applied by 2 emitters/tree with frequency varying season-wise. In summer (March–June) irrigation was applied at 1 day interval, in autumn (Oct–Nov.) at 4 days interval and in winter (Dec.–Feb) at 7 days interval. Trees did not receive any supplemental irrigation during rainy season (July–Sept.). Irrigation affected tree growth significantly (P< 0.05). All measured parameters (trunk height, trunk perimeter, trunk cross - sectional area and canopy volume) showed marked increase due to irrigation treatments over control. The best response in case of 2½ to 3½ years old trees was observed with 100% ET replacement. For 3½ to 4½ years old trees, effect of 75% ET replacement was comparable to that of 100%. The results indicated that the evaporative demand of the young trees varied with the age. Optimum growth response to applied water required changing the amount of water per unit canopy volume as the trees grew larger. Linear treatment responses were observed during both the years for all the characters, e.g. plant height, trunk girth and canopy volume.