Effect of some Biological Stimulants and Kaolin Particles Sprays on Fruit Retention, Productivity and Fruit Quality of Washington Navel Orange Trees

Abstract

This investigation was performed out during seasons 2016 and 2017 at private grove in El-Salhia El-Gadida, Sharkia Governorate, Egypt on 11 year-old Washington navel orange trees are growing in sandy soil under drip irrigation system. The effects of spraying salicylic acid (SA) (200 and 400 mg/L), Jasmine oil (JO) (2 and 4 ml/L), radish root extract (RRE) (50 and 100 ml/L) and Kaolin particles film (KPF) (5000 and 10000 mg/L) were studied on vegetative growth (leaf area index and leaf chlorophyll value), fruit set, fruit retention, productivity (yield as number and weight per tree), fruit quality parameters (fruit weight, fruit diameter, secondary fruit diameter, peel thickness, firmness, juice content, TSS, TA, TSS/TA ratio, ascorbic acid) and nutritional status (N, P, K and Ca contents). The current study clearly demonstrated that SA at all concentrations especially at 200 mg/L improved leaf area index, fruit retention, fruit number per tree, fruit yield, fruit firmness, juice content percentage, TSS, ascorbic acid and decreased the total acidity in orange juice, as well as increased nutritional status (N and P),. Also, a positive response in fruit retention, fruit weight, peel thickness, leaf area, chlorophyll value and N and P contents by foliar application of KPF at all concentrations under study. Moreover, Foliar sprays with JO at 2 ml/l and RRE at 100 ml/l significantly increased fruit set, fruit weight, fruit diameter, peel thickness, and lowered acidity percentage and increased Ca content.