GROWTH, FLOWERING AND CORM PRODUCTION OF GLADIOLUS (Gladiolus grandiflorus L.) AS INFLUENCED BY NITROGEN AND PHOSPHORUS
An experiment entitled “Growth, flowering and corm production of gladiolus (Gladiolus grandiflorus L.) as influenced by nitrogen and phosphorus” was carried out in the Experimental Farm, Department of Horticulture, Assam Agricultural University, Jorhat during 2019-2020. The treatments referred to four levels of nitrogen viz., 0, 5, 10 and 15 g/m2, four levels of phosphorus viz., 0, 3, 6 and 9 g/m2 and a constant dose of potassium viz., 6 g/m2. Hence, there were sixteen (4×4) combinations of various treatments of nitrogen and phosphorus and one additional treatment i.e. RDF (NPK::1:2:2 @ 56 g/m2) and each treatment was replicated three times in a Factorial Randomized Block Design. The mean performance of growth and yield parameters revealed that nitrogen level N3 (N 15 g/m2) recorded the maximum values for most of the growth as well as yield attributing characters viz. plant height (144.47 cm), number of leaves (8.14), breadth of leaves (5.35 cm), number of spikes per plant (1.78), length of spike (104.18 cm), flower diameter (10.36 cm), highest self-life (16.00 days) and vase life (11.33 days) and highest fresh weight of spike (90.93 g). In case of corm parameters, N3 (N 15 g/m2) also recorded maximum number of corms (1.87) and cormels (29.90) and highest weight (91.03 g) of corm. In respect of phosphorus levels, P3 (P2O5 9 g/m2) recorded the highest pant height (137.26 cm), number of leaves (7.82), breadth of leaves (4.92 cm), maximum number of spikes per plant (1.70), highest length of spike (100.35 cm), flower diameter (10.22 cm), self-life (15.39 days) and vase life (10.83 days), fresh weight of spike (84.62) and maximum weight of corm (84.28 g). Interaction between nitrogen and phosphorus showed that, N3P3 (N:P2O5 @ 15:9 g/m2) was superior in respect of the key parameters like plant height (147.24 cm), number of leaves (9.21), number of florets per spike (18.27), length of spike (107.52 cm), fresh weight of spike (97.46 g), self-life (16.80 days) and vase life (11.86 days) of spike and weight of corm (102.24 g) and cormels (13.65 g). From economic point of view, combination of N3P3 (N:P2O5 @ 15:9 g/m2) recorded the highest B:C ratio of 3.15 against the lowest B:C ratio of 1.52 in control treatment. Hence considering the best values in respect of vegetative, floral, corm characteristics and benefit-cost ratio, the treatment combination of nitrogen at 15 g/m2, phosphorus at 9 g/m2 and potassium at 6 g/m2 (Urea, SSP and MOP @ 32.6 g, 56.25 g and 10 g/m2) could be considered as the best treatment and can be effectively applied for commercial cultivation of gladiolus under Assam (Jorhat) conditions.