The Effect of Foliar Application of Zinc, Potassium, and Boron on Fruit Set and Retention in Kinnow Mandarin

Abstract

The study was conducted to assess the impact of foliar application of zinc (Zn), potassium (K), and boron (B) on the yield and quality of ‘Kinnow’ mandarin during 2023-2024 at the experimental orchard of the Department of Horticulture, CCS Haryana Agricultural University, Hisar. The aim was to address declining yields and fruit drop percentage due to improper nutrient management. The foliar treatments included zinc sulfate (ZnSO₄), potassium sulfate (K₂SO₄), and boric acid, either alone or in combination, applied to 10- year-old Kinnow plants. Key parameters measured included flowering time, fruit set, fruit retention, fruit drop, fruit size, and number of flowers per twig. The results indicated that the combined treatment of zinc sulfate (1.5%), potassium sulfate (0.5%), and boron (0.6%) was superior across all metrics, significantly improving vegetative growth, yield, and decline fruit drop percentage of tree. This treatment enhanced initial fruit set, fruit retention, and fruit size while reducing fruit drop or days taken for flowering. These findings suggest that proper nutrient application can significantly improve the productivity and quality of Kinnow mandarins. Zinc (Zn), boron (B), and potassium (K) are essential nutrients for fruit trees, playing critical roles in growth and fruit quality. Zinc is vital for enzyme activation, protein synthesis, and chlorophyll production, enhancing photosynthesis and reproductive success. Boron is crucial for cell wall formation, pollen tube growth, and nutrient transport, ensuring fruit set and preventing disorders like fruit cracking. Potassium regulates water balance, enzyme activity, and carbohydrate transport, contributing to larger fruit size, improved sugar content, and stress resistance. Together, these nutrients support optimal growth, fruit development, and high-quality fruit production.