SPRAY APPLICATION OF KNO3, LOW BIURET UREA, AND GROWTH REGULATORS AND HORMONES DURING AND AFTER FLOWERING ON FRUIT RETENTION, FRUIT SIZE AND YIELD OF MANGO

S.A. Oosthuyse
In a first experiment, the effect of foliar spray applications on 10-year-old ‘Tommy Atkins’ trees of potassium nitrate (KNO3), low biuret urea, GA3, CPPU, and NAA on fruit retention, average fruit weight, and tree yield at harvest was evaluated. Urea or KNO3 were sprayed during the inflorescence development period twice, and the growth regulators or hormones after flowering (fruits a pea size), but before the commencement of natural fruit drop shortly after flowering. KNO3 was applied at 4% (w/v), LB urea at 1% (w/v), GA3 at 40 ppm, NAA at 40 ppm and CPPU at 10 ppm, Applications were made singly or in combination. Pruning of the inflorescences during their development to prevent them from becoming large was also evaluated, as was a Boron formulation applied twice on the inflorescences they were developing.
In a second experiment, KNO3, LB urea, and growth regular and hormone spray applications on 10-year-old ‘Tommy Atkins’ trees were made after flowering just prior to the onset of fruit drop, when the fruits were “marble” size, with the same objective as the first experiment.
In a third experiment, KNO3 at 2 or 4% (w/v) was sprayed once or twice during the inflorescence development period on young ‘Tommy Atkins’, ‘Heidi’ or ‘Kent’ trees, again with the same objective as the first and second experiment.
In the first, the only treatment to result in a clear increase in fruit retention, fruit size and yield was inflorescence application of KNO3. Low biuret urea was phytotoxic, causing blackening of the flowers and developing ovaries. KNO3 + NAA + GA3 also noticeably increased fruit retention, but not tree yield. Inflorescence pruning gave rise to an increase in fruit size, but not retention. Boron application had no apparent effect. In the second experiment, CPPU + GA3 or NAA spraying apparently increased fruit retention. Both treatments increased yield. In the third experiment, KNO3 spray application always increased yield in increasing fruit retention.
KNO3 spray application during the inflorescence development period was considered the best option to reduce fruit drop after flowering and to increase tree yield.
Oosthuyse, S.A. (2015). SPRAY APPLICATION OF KNO3, LOW BIURET UREA, AND GROWTH REGULATORS AND HORMONES DURING AND AFTER FLOWERING ON FRUIT RETENTION, FRUIT SIZE AND YIELD OF MANGO. Acta Hortic. 1075, 135-141
DOI: 10.17660/ActaHortic.2015.1075.14
https://doi.org/10.17660/ActaHortic.2015.1075.14
NAA, GA3, CPPU, auxin, gibberellin, cytokinin, inflorescence, fruit drop
English

Acta Horticulturae