Improving Quantitative and Qualitative Traits of Table Grapes cv. ‘Fakhri’ with Foliar Application of Potassium Silicate and Humic Acid

Abstract

Foliar application of nutrients improves the performance and quality of grapes, and silicon is recently classified as an essential element for plants. For this purpose, a factorial experiment was conducted in a complete randomized design with three replications on grapes cv. ‘Fakhri’. The treatments included three levels of potassium silicate (0, 1000 [S.K1], and 2000 mg.L− 1 [S.K2]), combined with three levels of humic acid (0, 1000 [H1], and 2000 [H2] mg.L− 1). Morphological, physiological, and biochemical characteristics, as well as leaf microelements, were measured. The highest yield (10.56 kg/vine) was obtained with 2000 mg.L− 1 K2SO3×2000 mg.L− 1 humic acid. The interactive effects of these two treatments changed the activity of catalase, peroxidase, and superoxide dismutase, and the content of zinc, manganese, iron, and copper elements in grape leaves increased. This result indicates that potassium silicate and humic acid had a synergistic effect and increased all quantitative and qualitative indices of ‘Fakhri’ grapes studied in this experiment.