MSc

The experiment on ‘Chemical regulation of cropping in mango’ was taken up at Department of Pomology and Floriculture, college of Horticulture, Vellanikkara during September 2008 to June 2010.

The objective of the experiment was to regulate flowering and fruiting in mango varieties Prior and Alphonso using growth regulators and chemicals for sustained crop production and to ensure market supply. Alphonso and Prior varieties were selected for the study since they have alternate/irregular bearing habit but at the same time are superior and popular varieties in Kerala.

The treatments involved ethrel application alone and in combination with NAA, potassium nitrate alone and in combination with NAA, paclobutrazol alone and in combination with NAA as well as with KNO3. Paclobutrazol was applied as soil drench and all the other chemicals in the form of foliar sprays. Ethrel, potassium nitrate and paclobutrazol were applied once during September. NAA application at full bloom stage was included as treatments to tackle the premature fruit drop.

In both varieties, paclobutrazol treatments induced early and profuse flowering compared to control. The percentage of hermaphrodite flowers produced in an inflorescence was not affected by treatments in Prior. Paclobutrazol treatments significantly influenced the number of hermaphrodite flowers produced in the inflorescence of Alphonso. Inflorescence size was significantly influenced by different treatments in both varieties however, ethrel and potassium nitrate treatments were found effective in Prior and paclobutrazol treatments were the best in Alphonso.

Paclobutrazol treatments improved the initial fruit set in both varieties and were also highly effective in controlling fruit drop at different stages after fruit set. Fruit drop at 60 days after set ranged from 81.74 to 95.13% in variety Prior and 84.31 to 96.77% in variety Alphonso, the minimum values being recorded by paclobutrazol treatments.

During the second year of experiment (2009-10), rainfall during October-November resulted in poor flowering of mango in the state. The results of the present experiment showed that in trees under paclobutrazol treatments, flowering was good in both the varieties even under adverse climatic conditions which gives an indication that though weather conditions go unfavourable for flowering, the trees can be induced to get substantially good flowering by this chemical.

In the present study, quantitative (fruit weight, length, breadth and stone weight) and qualitative parameters (TSS, total sugars and acidity) of the fruits were not influenced by the different treatments in a specific pattern in both the varieties.

Irrespective of treatments and varieties, Carbohydrate/nitrogen ratio increased at monthly intervals after treatment and recorded maximum value just before flowering and finally reduced at the time of flowering. Paclobutrazol treatments recorded significantly higher values for this parameter in both varieties.

Overall perusal of the results clearly indicates the potential of paclobutrazol application @ 5g/tree to regulate flowering and fruiting in mango varieties Prior and Alphonso. The beneficial effects of the chemical noticed were early and profuse flowering, increased fruit set and reduced fruit drop in turn resulting in higher yield in both the varieties. Further trials involving other varieties of mangoes of different age groups at same location as well as in different locations are suggested as the future line of work in this aspect.