Effect of Foliar Application with Potassium Rates and Zinc Sources on Washington Navel Orange Trees

This investigation was carried out during two successive seasons (2020 and 2021) to study the effect of foliar application of potassium sulfate rates combined and different sources of zinc on Washington Navel orange (Citrus sinensis) trees grafted on sour orange rootstock (Citrus aurantium). Seven foliar spray treatments are conducted as follows: three different concentrations of potassium sulfate at 1, 2, and 3% combined with two sources of zinc: sugar alcohol zinc (SA-Zn) at 0.5% and chelated zinc (Zn-EDTA) at 0.5%, in addition to the control treatment. The best results were obtained by spraying potassium sulfate at 2% and sugar alcohol zinc (SA-Zn) at 0.5%, which was superior to improving tree nutritional status, fruit set percentage, yield efficiency, bio-chemical contents, mineral content of leaves and fruit quality.