الفهرس 
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Abstract
This study, was carried out during the season of (2000 and 2001), in a private vineyard located at ElDear village near Aga city, ?Dakahlia Governorate,? on 15 years old of Thompson Seedless grapes. The main object of this investigation was to study the effect of potassium fertilization each alone or with summer pruning on bud behavior, vegetative growth, yield, berry quality and leaf petioles and cane nutrient composition, in order to obtain highest yield with best quality of clusters. The obtained results could be summarized as follows: I.? Effect of Potassium application and summer pruning on bud behavior and vegetative growth: ? A.?Bud behavior: Potassium fertilization and summer pruning gave an increase in the percentage of bud burst, bud fertility and fruitfullness, so the treatment of 150gm.k2o/vine with summer pruning gave the highest percentage. B.?Vegetative growth: Potassium fertilization at 150gm.k2o/vine gave the highest effect in trunk growth, leaf area, internodes length and internodes thickness, yet summer pruning gave a little effect in this respect . II.? Effect of Potassium application and summer pruning on yield and berry quality ? A.? Potassium fertilization and summer pruning gave an increase in yield per vine and per feddan, so the treatment of 150gm.k2o with summer pruning gave a higher percentage of yield per vine and per feddan, also gave a higher values in cluster weight and size. B.? Potassium fertilization at 150gm/vine, each alone or with summer pruning significantly increased the berry weight and size, also potassium fertilization at 150gm.k2o/vine gave the highest percentage of SSC , SS/acid ratio and the lowest percentage in total acidity, but the treatment of summer pruning did not gave any effect in this respect. III.? Effect of Potassium application and summer pruning on leaf petioles and cane chemical composition. A.?Leaf petioles chemical composition. Potassium fertilization increased the a mount of NPK in leaf petioles by increasing the level of potassium , but potassium fertilization decreased the a mount of Ca and Mg in leaf petioles by increasing the level of Potassium, where as the treatment of summer pruning did not gave any effect in this respect. B.? cane chemical composition. Potassium fertilization significantly increased total carbohydrates and C/N ratio in canes by increasing the level of potassium fertilization each alone or with summer pruning, also potassium fertilization at 150gm.k2o/vine gave a higher percent of total nitrogen in canes. Yet, summer pruning gave no significant effect in this respect. from the abovementioned results, it can be safely say that, potassium fertilization when treated as soil application at the rate of 150 gm K2O/vine each alone or with summer pruning gave the best effect in bud behavior, vegetative growth, yield, berry quality, leaf petioles, and cans chemical composition under ?Dakahlia Governorate? conditions. So that, we can recommended our growers to added 150 gm K2O/vine with summer pruning in order to improve both productively and quality of Thompson Seedless grapes.