Effects of phosphorus and potassium fertilization and fruit canopy position on sugar accumulation in mangifera indica cv. 'Kent' pulp

Abstract

Sugar content is the key to mango quality and growers are constantly seeking methods to optimize it. In this study, fructose, glucose, sucrose, and maltose sugars were evaluated to determine how phosphorus and potassium fertilizers in varying amounts could affect these sugar levels and how sunlight exposure effects fruit. The experiments were conducted in the KALRO Orchard of Kiambu County, Kenya. Thirty-five healthy 7- to 8-year-old ‘Kent’ trees were selected and divided into five treatment groups with five replicates each. Treatment with 1 kg, 2 kg P, K and combined PK per tree resulted in a significantly higher fructose content than the control. In contrast, neither 1 kg nor 2 kg P resulted in significantly higher glucose contents than the control. Combined PK fertilizers at 0.5+0.5 kg per tree reduced fructose and increased glucose, sucrose, and maltose. A combination of PK fertilizers at 1.0+1.0 kg significantly increased only fructose, but not other sugars. Even after applying P and K fertilizers, the position of the fruit canopy did not affect fructose, glucose, or maltose contents. However, there was a trend towards a higher sucrose content in fruits exposed to sunlight (5.17 g/100 g) than in canopy fruits (2.29g/100g), although this difference was not statistically significant. The same trend was observed for the other sugars. The t-test revealed no significant differences between the two canopy positions (t = 1.01, p = 0.344). A significant difference in sugar content (p < 0.05) between fruits harvested at different canopy positions suggests that fruits harvested at different canopy positions did not ripen simultaneously. In contrast, neither 1 kg nor 2 kg of P produced a significant difference in the glucose content. Combining PK fertilizers at 0.5+0.5 kg per tree decreased fructose while increasing glucose, sucrose, and maltose. A combination of PK fertilizers at a rate of 1.0+1.0 kg significantly increased only fructose but not other sugars. Even after the application of P and K fertilizers, the position of the fruit canopy did not affect fructose, glucose, and maltose contents. However, there was a trend towards a higher sucrose content in fruits exposed to sunlight (5.17 g/100 g) than in crown fruits (2.29 g/100 g), although this difference was not statistically significant. The same trend was observed for the other sugars. The t-test revealed no significant differences between the two canopy positions (t = 1.01, p = 0.344). A significant difference in sugar content (p< 0.05) between fruits harvested at different canopy positions suggests that fruits harvested at different canopy positions did not ripen simultaneously.