B. Chalise^*, R.L. Shrestha*, K.P. Paudyal^** and H.P. Subedi<sup>*

*</sup>National Citrus Research Program, Paripatle, Dhankuta
^**Horticulture Research Division, Khumaltar, Lalitpur

Abstract

A field experiment was conducted at National Citrus Research Program, Paripatle, Dhankuta during 1^st November, 2004 to 1^st September, 2005 to determine the effect of different doses of GA₃ and nitrogen under open and plastic tunnel condition on growth of trifoliate orange seedling. The experiment was laid out in two Factorial split-plot design consisting three replications of each Treatment. The open and plastic tunnel was considered as the main plot factor (Factor-A) and the combination of different doses of gibberellic acid (GA₃) and nitrogen as sub plot factor (Factor-B). The treatments were applied in seedlings two months after germination. Seedlings were planted at 15x10 cm spacing in 90 cm x80 cm sized experimental plots supplied initially with 5 kg FYM per plot containing 48 plants. White transparent plastic sheets were used for covering the plant in the form of tunnel. GA₃, was applied as foliar spray at one month intervals while nitrogen was applied through urea as soil application at two split doses in 1st April and 1^st May. Ten sample plants were selected for the study from each bed. From the study, it was found that the growth of seedling of trifoliate orange was highly accelerated under the plastic house condition as compared to the open condition. The height of seedling (47.75 cm), number of leaf per plant (25.27) and size of seedling diameter (5.193 mm) were found highest at 300 days after sowing under plastic tunnel condition. Similarly, the highest growth of seedling height (48.81 cm), number of leaf per plant (27.20) and seedling diameter (5.383 mm) were observed in 120 ppm GA₃ and 400 kg nitrogen/ha combination at similar age of the seedling.

Keywords: Poncirus trifoliata, Plastic tunnel, GA₃, nitrogen and accelerated growth