IMPACT OF SPRAYING WASHINGTON NAVEL ORANGE TREES WITH COBALT, SELENIUM AND SILICON SALTS ON VEGETATIVE GROWTH, PRODUCTIVITY AND FRUIT QUALITY

Abstract

A study was carried out during two successive seasons, 2012 and 2013 on 7 years old Washington Navel Orange trees (Citrus sinensis) budded on sour orange rootstock (Citrus aurantium, L.) and planted at 5 x 5 meters under basin irrigation system. The trees are grown in a private orchard located at El-Kalubia Governorate Egypt. The study involved three experiments as follows: The first experiment: Impact of spraying cobalt sulphate on vegetative growth, fruit set%, fruit drop%, productivity, fruit quality, leaf mineral concentrations and enzymes activity of Navel orange trees. This experment inculded five levels of cobalt (0, 5,10,20 and 40 ppm ) as cobalt sulphate (CoSO4). Selected trees were sprayed twice in each season ( the first week of each Mar. and Sept.). The experiment was arranged in a randomized complete block design with four replicates. Results indicated that 20 ppm Co gave the highest values of yield/tree, fruit weight, total soluble solids, leaf N, P, K, Ca, Mg, Zn, Mn and Co content as compared to the control treatment which gained the lowest values. The second experiment: Impact of spraying sodium selenite on vegetative growth, fruit set%, fruit drop%, productivity, fruit quality, leaf mineral concentrations and enzymes activity of Navel orange trees. This experment inculded five levels of selenuim (0, 20,40,80 and 160 ppm) as sodium selenite (20% Se) (Na2SeO3, 5H2O). Selected trees were sprayed twice in each season ( the first week of each Mar. and Sept.). The experiment was arranged in a randomized complete block design with four replicates. Results indicated that 40 ppm selenium gave the highest values of yield/tree, fruit weight, total soluble solids, leaf N, K, Ca, Mg, Fe, Zn, Mn and Se content as compared to the control treatment which gained the lowest values.