Abstract
Two field experiments, each repeating for three times, were conducted to determine the influence of paclobutrazol, urea and potassium nitrate on the regularity in bearing, yield and quality of mango cvs. Khirsapat and Ashwina at the Regional Horticulture Research Station, Chapai Nawabganj during 2006 to 2008. The first experiment comprised six treatments, viz., Control, paclobutrazol @ 10 g a.i/tree, paclobutrazol @ 10 g a.i/tree +2% KNO3, paclobutrazol @ 10 g a.i/tree + 2% urea, 2% KNO3 and 2% urea which were applied to the mango tree cv. Khirsapat. Wide variations were observed among the treatments in respect of morphology, flowering, fruiting, yield, fruit quality and regularity in bearing of mango. The treatments, paclobutrazol @ 10 g a.i/tree + 2% KNO3 and paclobutrazol @ 10 g a.i/tree + 2% urea produced the highest percentage of uniform flowering followed by application of paclobutrazol @ 10 g a.i/tree compared to control in both the 'on and off years of mango production during 2006 to 2008. Maximum fruit yield in terms of number and weight per tree was produced by the same treatments in all the experimental years. All the paclobutrazol treatments (paclobutrazol @ 10 g a.i/tree, paclobutrazol @ 10 g a.i/tree + 2% KNO3 and paclobutrazol @ 10 g a.i/tree + 2% urea) exhibited higher number of fruit set per panicle and higher percentage of fruit retention, but reduced tree vigour, individual fruit weight and fruit size and enhanced fruit quality. Age of tree and dose of paclobutrazol in cv. Ashwina of experiment no.2 had also significant influence on the above parameters. Paclobutrazol @ 1.5 g a.i/m canopy dia caused reduction in shoot and inter-nodal length, leaf size, leaf area and also tree vigour. It advanced bud initiation as well as flowering in mango trees by about two weeks over control treatment. Paclobutrazol increased the percentage of flowering in both the 'on and off years of mango production irrespective of doses used. Higher percentages of fruit retention both at marble and harvest stages were observed by the lower dose of paclobutrazol (1.0 g a.i/m canopy dia). Application of paclobutrazol at both doses (paclobutrazol @ 1.5 g a.i/m canopy dia and paclobutrazol @ 1.0 g a.i/m canopy dia) increased the fruit yield in terms of both number and weight per tree. Higher dose of paclobutrazol caused more reduction in fruit weight, fruit size and stone weight, but produced more adverse effects on vigour in younger trees. It caused earlier harvesting of fruits but reduced the shelf life of mango fruit. The effects of the treatments on the above parameters were found in the order of paclobutrazol @ 10 g a.i/tree + 2% KNO3 > paclobutrazol @ 10 g a.i/tree + 2% urea > paclobutrazol @ 10 g a.i/tree > 2% KNO3 > 2% urea > control. The application of paclobutrazol enhanced regularity in bearing especially in older mango trees.