Efficacy of Foliar Applications of Salicylic Acid, Zinc and Potassium on Reducing Fruit Drop, Yield Improvement and Quality of Balady Mandarins

THE OBJECTIVE of the present study was to evaluate the effects of Salicylic acid (SA), Zinc (Zn) and Potassium (K) on reducing fruit drop and improving fruit quality of Balady mandarin (C. reticulata, Blanco) at flowering initiation, fruit sized 5 mm and at pre-coloring stage. The experiment was conducted in a commercial orchard in Sharnoob, Behera governorate where 30-year- old trees budded on sour orange rootstock were sprayed with SA at 10mg/L, zinc sulfate at 0.02% and potassium sulfate at 0.25% separately or in combinations. The results showed that K applications alone or combined with SA led to the best results regarding the yield evidenced as fruit number or by weight resulting from markedly increased fruit retention  after June drop and final fruit retention percentages. The latter treatment was statistically superior in increasing fruit set followed by Zn or SA solely. All treatments reduced fruit drop, SA separately or plus K or Zn reduced fruit drop than the control treatments. No definite results were obtained concerning fruit physical properties i.e. weight of fruit or peel, fruit length and diameter. However, Zn and Zn plus SA applications significantly increased TSS and TSS/acid ratio, as well as K treatments increased TSS and V.C. as compared to control. Lastly, K or Zn treatments and their combinations with SA resulted in considerable higher values in leaf k and Zn content.