Effect of potassium fertilizers and Humic acid on the Pigments and activity of antioxidants in grape Bidaneh Sefid

Grape production with high quality, firm texture and suitable shelf life of the fruit is very important. The purpose of this study, the effect of foliar application of different concentrations (0, 1000 and 2000 mg/liter) of potassium sulfate, potassium nano chelated fertilizer and humic acid on the pigments and antioxidant activity in grape variety 'Bidaneh Sefid' were studied in order to improve the quality of grapes in a completely randomized design in a commercial orchard during 2013-2015. Foliar applications were employed three times, including one before flowering, at fruit set, two weeks after fruit set and one month after the second stage was carried out. Based on the results, potassium sulfate at a concentration of 2000 mg /liter increased the potassium concentrations of leaves, potassium nano chelated fertilizer at a concentration of 1000 mg/liter increased chlorophyll in leaves, anthocyanins in leaf and humic acid with a concentration of 1000 mg /liter increased the phenol concentration, and flavonoid in leaf compared to control. potassium nano chelated fertilizer at a concentration of 1000 mg/liter increased anthocyanins in fruit and superoxide dismutase and also, treatment of potassium nano chelated fertilizer at a concentration of 2000 mg/liter increased the potassium and activity of the enzyme ascorbate, potassium sulfate. Concentration of 1000 mg /liter potassium nano increased the phenol concentrations in fruit, protein and catalase activity. Humic acid at concentration of 1000 mg /liter increased the phenol concentration in leaf, flavonoids in fruit and peroxidase activity compared to control. Results of this study, confirmed a significant effect of treatments, especially potassium nano chelated fertilizer and potassium sulfate at a concentration of 1000 mg/liter on increased enzyme activity. As a result, it strengthens membranes and tissues and thus increased the quality of the fruit.