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Leaf and fruit nitrogen, potassium, and calcium concentrations in relation to fruit yield, quality, and severity of anthracnose in mango (Mangifera indica L.)
Thesis Abstract:
The effect of pre-harvest nitrogen fertilization on the post-harvest disease, yield, and fruit quality was determined on 10–15-year-old ‘Carabao’ mango trees. The treatments included four levels of nitrogen (0, 100, 200, and 300 g) and two foliar fertilizers (2.4% potassium nitrate (KNO3) and 3% calcium nitrate (Ca(NO3)2) as supplementary nitrogen sources.
The application of KNO3 and Ca(NO3)2 increased the number of fruits per panicle. The highest yield was obtained from trees treated with 200 g N tree-1. Fruit weight, flesh weight, and peel weight significantly increased with nitrogen levels and its combination with KNO3 and Ca(NO3)2 foliar applications.
Nitrogen fertilization did not significantly affect leaf nitrogen concentration but was highest (1.47%) in 300 g N tree-1. Nitrogen fertilizer and its combinations with KNO3 and Ca(NO3)2 also did not affect the leaf K and Mg concentration. Higher leaf Ca concentration was observed when trees were sprayed with Ca(NO3)2. Peel analysis showed no significant variations on the peel nutrient concentrations as affected by different treatments. All trees treated with KNO3 resulted to higher peel K concentration.
The quality of fruits was significantly affected by nitrogen fertilization and its combination with foliar Ca(NO3)2 and KNO3 application. Higher nitrogen fertilization increased the total soluble solids of fruit and decreased fruit pH. Nitrogen fertilization did not affect the titratable acidity. Fruits were relatively firmer and slower to ripen in 300g N tree-1 + Ca(NO3)2 than other treatments. Longer shelf life (nine days) resulted from CaNO3 foliar spray.
The incidence and severity of anthracnose were highest in the fruits obtained from higher levels of nitrogen but those were reduced when N was combined with Ca(NO3)2. The severity and incidence of stem-end rot fluctuated with N fertilization and its combinations with KNO3 and Ca(NO3)2 foliar applications. No relationship was established between leaf and peel nutrient concentrations, and incidence and severity of post-harvest disease.