Effect of Foliar Application of Cytokinin, Active Dry Yeast and Potassium on Fruit Size, Yield, Fruit Quality and Leaf Mineral Composition of Valencia Orange Trees

A FIELD experiment was conducted during two successive seasons of 2013/2014 and 2014/2015 in a private orchard located at Sharnoob village, El-Behera governorate, Egypt, this study aim to evaluate the effect of foliar application of benzyladenine, yeast extract and potassium solution on yield, fruit quality and leaf mineral content of Valencia orange trees (Citrus sinensis, osbeck) about 50 years old budded on sour orange (C. aurantium, L) rootstock planted in clay soil. The obtained results proved that spraying trees with a mixture of (BA 40 ppm+ yeast 0.4% + K 0.4%) resulted in a higher number of fruit set/branch, although it caused an increase of fruit juice acidity compared with the control and the differences were significant during both seasons of the study. Also, this treatment, significantly increased fruit length and diameter, only in one season. Moreover, benzyladenine spray treatment at 40 ppm, in both seasons, produced the highest number of fruits/tree, an average fruit weight and yield and participated with potassium at either 0.2 or 0.4% to improve fruit shape (fruits were more circular in shape). In most cases, BA 40ppm spraying treatment markedly increased fruit length, and fruit growth rate comparing to control treatment. The data also revealed that Valencia orange trees sprayed with a combination of (BA 20ppm + yeast 0.2% +K 0.2%), in both seasons, gave significantly higher fruit diameter and fruit growth rate in most measuring dates, increased vitamin C content in the fruit juice. Trees sprayed with dry yeast extract at 0.2%, in both seasons, markedly increased total soluble solid percentages in fruit juice. In addition, potassium spray treatment at 0.4% markedly increased fruit diameter, only in one season and participated with benzyladenine at 40ppm and dry yeast extract at 0.2% to improve fruit physical properties (length, diameter, pulp and rind weights, fruit weight and juice volume). Different foliar application increased total nitrogen, phosphorus and potassium in the leaves. Trees sprayed with a mixture of (BA 20ppm+ yeast 0.2%+ K 0.2%) and 0.4% potassium solution treatment, in both seasons, significantly increased leaf total nitrogen content as well as potassium spray treatments at either 0.2% or 0.4%, markedly increased leaf phosphorus and potassium content.