Effect of growth regulators and certain formulations on bunch development in banana var. palayankodan

Abstract

The yield of banana in Kerala remains very low inspite of the adoption of proper manuring and other management practices. Investigations have indicated that the main barrier to the increased production in banana is the lack of sufficient leaf area at the active phase of growth of the plants. The present experiment was conducted with the banana cultivar ‘Palayankodan’ under sparsely irrigated conditions with a view to increase the plant growth and ultimate yield by the use of growth regulators and commercially available formulations. The growth regulators viz., 2-4-D and NAA and the commercially available formulation namely ‘Navras Banana Special’ were tried at four different concentrations as given below:- 2,4-D - 5,10,15 and 20 ppm NAA - 20, 30,40 and 50 ppm ‘Navras’ - 0.25, 0.50,0.75 and 1.00 per cent The various chemicals at different concentrations were applied as two foliar sprays at three and four months after planting. A third spray was also given on the bunches immediately after the female phase of flower opening. On an overall analysis, 2,4-D at 20 ppm and ‘Navras’ at 0.50 per cent were found to be more effective in promoting the vegetative growth of plants. With respect to flowering and duration of the crop, the growth regulators alone had significant effects when compared to the commercial preparation ‘Navras’. The effectiveness also depended on the concentrations of the growth regulators. Thus 2,4-D at 20 ppm induced early shooting of plants by about 12 days whereas NAA at 50 ppm caused substantial delay in shooting. The chemicals at their various concentrations were not effective in influencing the bunch maturity, thus indicating that the applied chemicals caused the earliness or delay observed, through their influencedon the vegetative growth only. Consequent to the application of 2,4-D at 20 ppm the crop duration was advanced by 22 days. Contrary to this, NAA at 50 ppm delayed the duration of the crop. The treatments with 2,4-D at 5 to 20 ppm, NAA at 40 and 50 ppm and ‘Navras’ at 1.00 per cent were found to advance the ripening of fruits. The best quality fruits in terms of TSS and total sugars were obtained by the application of 2,4-D at 20 ppm. Among the concentrations of ‘Navras Banana Special’, o.5 per cent gave the best results with respect to the growth and yield of plants. When the concentration was increased further, there was a decrease in the performance of the plants. The optimum doze of ‘Narvas Banana Special’ was worked out to 0.534 per cent. The correlations worked out from the data collected revealed that the vegetative and bunch characters such as girth of psuedostem, number of functional leaves, total leaf area, length of bunch, number of hands and fingers per bunch, number of fingers per hand and weight of hand, length, girth and weight of fingers amply contributed to the overall yield in the form of bunch weight. The yield increase observed in the present study due to the application of 2,4-D at 20 ppm was by 88 per cent and that for ‘Navras’ at 0.5 per cent was by 96 per cent. The benefit/cost ratio worked out for these treatments did not differ and hence application of 2,4-D (20 ppm) and ‘Navras Banana Special’ (0.5 per cent) were equally good for increasing the yield. The present investigations were conducted under sparsely irrigated conditions where, irrigation was given just for the maintence of the crop. Further investigations with rainfed and irrigated ‘Palayankodan’ bananas may be of particular interest.