Effect of potassium and boron nutrition on some quantitative and qualitative characteristics of grape cv. Askari

Optimal nutrition of grapevine is one of the most important factors that affect the quantity, quality and time of fruit ripening. In order to increase the quantity and quality of ‘Askari’ cultivar, a factorial experiment in a randomized complete block design with three replications was conducted at Shahrekord in 2010. Treatments consisted of four levels of potassium sulfate fertilizer (0, 300, 600 and 900 g per vine) and four levels of boric acid fertilizer (0, 1000, 2000, and 3000 ppm). The results showed that potassium had a significant effect on yield and yield components. Different levels of potassium sulfate and boric acid increased cluster (number, weight, length, width) and fruit soluble solids. With increasing potassium levels, the number of clusters (14, 18 and 25) and content of total soluble solid (0.54, 1.45 and 1.53%) were significantly increased in comparison with control, respectively. Also, total soluble solids of berries were increased significantly (0.76, 0.75 and 1.25%) with boron treatment compared to control. The highest TSS (18.8) obtained in 900 mg of potassium sulfate per square meter, while it caused the greatest reduction in fruit acidity compared with the control. Fruits pH was decreased by 0.3 units with application of 3000 ppm of boric acid. The results of this experiment showed that nutrient treatments, especially potassium sulfate accelerated fruit ripening and increased fruit yield and sugar content.