Ten years old ‘Balady’ mandarin trees, grown under sandy soil conditions in Egypt, were sprayed with 1% or 2% potassium nitrate or di-potassium hydrogen phosphate twice at the beginning of April and ten weeks later (mid June) and treated with girdling before blossoming (late Dec.). The experiment was arranged in a complete randomized design with three replicates, each consisted of three trees. Results concluded that girdling plus potassium sprays specially potassium nitrate at any concentration had a positive effect on nitrogen and potassium percentages, total carbohydrate, total chlorophyll and chlorophyll (a) content in the leaves, which reflected on increasing fruit weight, number of fruits per tree and finally yield weight per tree. In this 2-years trial, spraying trees with potassium nitrate either at 1% or 2% increased yield per tree on average with 23% and 26%, respectively, compared to girdling only (Table 1 and 2). The potassium treatments also enhanced fruit volume, soluble solids content and SSC/acid ratio. Results showed that at any concentration KNO3 outperformed K2HPO4 in terms of yield and number of fruits per tree in both seasons.
Table 1. Effect of girdling and different potassium sprays on yield and fruit characteristics of Balady mandarin trees during 2002.
Table 2. Effect of girdling and different potassium sprays on yield and fruit characteristics of Balady mandarin trees during 2003.