Citrus response to various foliar potassium treatments

Abstract

This study aimed to investigate the effects of foliar application of different potassium (K) sources on yield and fruit nutrient uptake in 28-year-old Valencia oranges (Citrus sinensis, L.) grafted onto Trifoliata citrange rootstock. In the trial that was conducted with different foliar potassium sources in the region of Köyceğiz (Turkey) in the years 2016, 2017, and 2018 with 5 replications according to the random blocks trial design for this purpose, in addition to the control group where no foliar treatment was applied, the treatment groups received Potassium Nitrate (KNO3, 46% K2O; 300 g/100L/da), Potassium Thiosulfate (25% K2O; 400 ml/100L/da) and Potassium Phosphite (25% K2O; 500 ml/100 L/da) treatments. For all examined parameters and for all 3 years, the highest results were obtained in the potassium phosphite treatment. This may be due to its higher mobility inside the plant compared to other K sources. The effects of all treatments on yield were found significant, where the yield values for 2016, 2017, and 2018 were found as 139, 143, and 140 kg/tree, respectively. This may be explained with the role of K on promoting the fruit reserves. Regarding the effects of potassium phosphite on all fruit nutrient uptake amounts, the effect of the treatment in all 3 years was found significant except for Fe, Cu, and Mn. In conclusion, among the potassium sources, the most effective fertilizer was determined as potassium phosphite.