Effect of KNO3 sprays to flowering mango trees on fruit retention, fruit size, tree yield, and fruit quality

In South Africa, the mango cultivars 'Tommy Atkins,' 'Kent,' and 'Heidi' retain few fruit relative to the cultivars 'Sensation,' 'Irwin,' and 'Keitt.' In the present study, the effect on fruit retention, fruit size, tree yield, and fruit quality of applications of KNO3 to trees of the former cultivars whilst they were flowering was investigated. A KNO3 spray at 2 or 4% was administered either once during the flowering period, i.e., when the inflorescences were in bloom, or twice during this period, i.e., when the inflorescences were actively extending and subsequently when they were in bloom. In 'Tommy Atkins', the greatest increase in fruit retention occurred following the single application at 4%. In 'Heidi', two applications at 4% each gave rise to the greatest increase, and in 'Kent', two applications at 2% each increased fruit retention the most. In every cultivar, slight reductions in average fruit weight (final fruit size) were associated with the increases in fruit retention found. KNO3 increased tree yield in each cultivar. The greatest increases in yield corresponded with the greatest increases in fruit retention found. There was no apparent effect of the KNO3 sprays on fruit quality (ground skin colouration, total soluble solids content, pH, or taste on ripening). Inflorescence application of KNO3 to the cultivars in question is now adopted commercially in South Africa.