Effect of P-K Fertilizer Rate and Fruit Canopy Position on Fruit Quality and Vitamins of Mangifera Indica Cv. 'Kent'

Abstract

Mango production in Kenya is hindered by poor fruit quality and imbalanced fertilizer application, hence the need to investigate the long-term effects of different fertilizer regimes on nutrient cycling, and overall mango orchard sustainability. This study aimed to determine the effects of phosphorus (P) and potassium (K) fertilizers, as well as fruit canopy position, on the nutritional content and morphological characteristics of 'Kent' mango fruits. Seven treatments, P1kg, K1kg, P2kg, K2kg, PK1kg, PK2kg, and control, were repeated five times, resulting in 35 test trees of the "Kent" cultivar, aged 7-8 years. The results indicated that increasing P application significantly boosted β-carotene levels (p ≤ 0.05), while ascorbic acid levels were reduced. However, both β-carotene and α-tocopherol levels were higher in control trees compared to fertilized trees, regardless of the fertilizer type or rate. A weak negative correlation between ascorbic acid and α-tocopherol was observed (r=-0.48, P≤0.05), suggesting a potential trade-off between these two antioxidants. Additionally, fruit weight was strongly correlated with skin weight, stone thickness, and seed thickness. Fruits from within the canopy generally exhibited higher levels of antioxidants than those exposed to direct sunlight. The study provides valuable insights into the influence of P and K fertilizers and canopy position on mango fruit quality. However, further research is needed to optimize fertilizer management practices for sustainable mango production in Kenya.