FRUIT SET AND QUALITY OF 'NAVELINA' ORANGES UNDER DIFFERENT TREATMENTS

Generally, in citrus production in moderate climates flowering is abundant, however fruit set is often low, rarely exceeding 10% of formed flowers. Therefore, this work was done aiming to increase fruit set of citrus trees ‘Navelina’ by using different treatments to increase fruit set and measuring effects in different geographical quadrants of the trees. The experiment was carried out in Maçambará/RS at 29°7’57”S, 56°10’38” W and an altitude of 57 m. An orchard of Navelina grafted on trifoliate lemon was used during two consecutive crops. The orchard was planted in 2004 at 5×4 m spacing (500 tree/ha). According to the classification of Köppen the local climate is Cfa. A completely randomized design with three replications in a 7×4 factorial arranged distributed of seven treatments was used: 1) Control, 2) branch girdling, 3) promalin phytoregulator (benzyladenine + giberellins + AG₄ + AG₇), 4) Boron, 5) Boron + branch girdling, 6) Boron + Promalin, and 7) Boron + Promalin + branch girdling and four geographical quadrants (North, South, East and West). According to the results an interaction among treatments for fruit set was verified. In general, treatment 5 (Boron + branch girdling) showed the best fruit set results, except in the East quadrant. Other variables measured did not show significant differences. Fruit height and diameter averaged 78.1 and 85.2 mm, respectively; fruit weight was 214 g; total soluble solids was 12.5°Brix and fresh and dry matter of flesh had values of 270.5 and 13.4 g, respectively. For the different quadrants, the best results regarding different treatments occurred in the East and South. The use of Boron + girdling improved fruit set of ‘Navelina’, the use of Promalin provided fruit with thinner peel and the combination of Boron + Promalin + branches girdling had the highest yield.