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

Grape (Vitis vinifera L.) is an important fruit crop and is widely cultivated because of its nutritional and economical values. The 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 (0.0, 1.0 (S.K1), and 2.0 g/L (S.K2)), combined with three levels of humic acid (0.0, 1.0 (H1) and 2.0 (H2) g/L). Morphological, physiological and biochemical characteristics, as well as the microelements of the leaves were measured. The highest yield (10.56 kg/vine) was obtained by simultaneous treatment with S.K2 and H2 solutions. The interactive effects of these two treatments changed the activity of catalase, peroxidase and superoxide dismutase and increased the content of zinc, manganese, iron and copper elements in grape leaves. 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. [ABSTRACT FROM AUTHOR]