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FOLIAR APPLICATION OF LOW-BIURET UREA AND FRUIT CANOPY POSITION IN THE TREE INFLUENCE THE LEAF NITROGEN STATUS AND PHYSICO-CHEMICAL CHARACTERISTICS OF KINNOW MANDARIN (CITRUS RETICULATA BLANCO)

AHMAD S. KHAN^1*, A.U. MALIK¹, M.A. PERVEZ¹, B.A. SALEEM¹, I. A. RAJWANA, T. SHAHEEN³ AND R. ANWAR¹

Abstract: Experiments were conducted to study i) the influence of supplemental foliar application of low-biuret urea (LBU) on the leaf nitrogen status and fruit quality and ii) the role of fruit canopy positions in the trees on the physico-chemical characteristics of Kinnow mandarin fruit. In first experiment, foliar application of LBU twice (before blooming and after fruit set) significantly brought the leaf N content of the Kinnow trees from deficient to optimum level as compared to single application before blooming or after fruit set and control trees. Trees sprayed with LBU twice also exhibited higher juice and pulp weight compared to other treatments. However, other quality parameters were not significantly affected with LBU application. Results of second experiment revealed that fruit harvested from inside of the tree canopy exhibited higher fruit volume; fruit, peel and pulp weight in contrast to the fruit harvested from other canopy positions. Highest juice percentage was recorded for fruit harvested either from top or outer periphery of the tree canopy. Soluble solids content (SSC), SSC: titratable acid ratio; reducing, non-reducing and total sugars; ascorbic acid contents were higher for fruit harvested from the top of the tree canopy as compared to the fruit harvested from other canopy positions. In conclusion foliar application of LBU can be used effectively to increase the leaf N status of Kinnow trees. Fruit at different canopy positions vary in their physico-chemical characteristics at harvest and should be harvested separately to have uniform quality and get maximum economic return.

¹Institute of Horticultural Sciences, University of Agriculture, Faisalabad, Pakistan

²University College of Agriculture, Bahauddin Zakariya University Multan, Pakistan

³National Institute for Biotechnology & Genetic Engineering, PO Box 577 Jhang Road, Faisalabad, Pakistan