Supplementation of Potassium and Phosphorus Nutrients to Young Trees Reduced Rind Thickness and Improved Sweetness in ‘Kinnow’ Mandarin Fruit

Young ‘Kinnow’ mandarin orchards have inferior fruit quality in terms of thick rind, less juice and low eating quality. The present research experiment was aimed at evaluating the effect of phosphorus (P) and potassium (K) nutrients on rind and fruit quality at different harvesting times. Young trees (6 years old) were supplied with fertilizers containing P (P 2 O 5 = 552 g and 828 g) and K (K 2 O = 600 g and 900 g) nutrients at the fruit set stage. For yield and physical quality assessment, fruits were harvested at commercial maturity (second harvest). Trees showed maximum yield in terms of fruit number and weight subjected to K 2 O (600 g). Rind thickness was promisingly reduced by soil amendment of K 2 O- 600 g followed by K 2 O- 900 g as compared to control trees. Biochemical, phytochemical and sensory attributes were assessed at three times of harvest. Soluble solids content and sugar acid ratio of fruit were positively increased in K‑treated trees followed by those subjected to P nutrient and gradually increased as harvesting time was prolonged. Among phytochemicals, K 2 O- 600 g showed higher DPPH (2,2-diphenyl-1-picrylhydrazyl) activity and P 2 O 5 - 552 g application increased the total phenolics content of fruit, but declined at third harvest. Sensory properties (taste, flavor, aroma and texture) were improved in all treatments except control. Conclusively, the results revealed that the optimum range of fertilizers containing K and P nutrients can increase the productivity of young trees and improve the fruit quality of ‘Kinnow’ mandarin.