Effect of Potassium Foliar Spray on Two Plum Trees Cultivars: 'Strival' and 'Black Star'

Potassium is an essential mineral nutrient for plum fruit growth and quality. Foliar sprays have begun to be used by fruit growers in addition to soil applications. This study was undertaken in order to evaluate the effects of potassium foliar applications, as the only method of fertilization used, on growth, yield, fruit quality and mineral status of 'Strival' and 'Black Star' plum tree cultivars. Potassium as potassium sulfate was applied by foliar sprays at (50 and 100%) of the tree's estimated requirements. The foliar sprays were split according to the various critical stages of the fruits' growth. Another treatment using fertigation as the potassium fertilization method was also observed. In this treatment, 100% of the potassium tree requirement was given. The results showed that the foliar sprays did not have a significant effect on vegetative growth. The two foliar sprays at 50 and 100% led to an increase of fruit weight. An improvement of solid soluble contents was also observed for the potassium foliar spray treatment. No significant effect was observed on the foliar mineral content for the different mineral elements either between the three treatments or for the two cultivars.