Effects of Potassium Sulfate Soil Drench and Foliar Application of Magnesium Sulfate on Grapevine Tolerance to Artificial and Spring Frostbite

Low temperature, causing heavy damage to vineyards from different regions of the Iran every few years. The use of potassium fertilizer, regardless of other elements, cannot provide proper nutrition for grapevine. The main purpose of this investigation was to study effects balanced nutrition and its effects on vines (Bidaneh Sefid cultivar) tolerance to frostbite. Grapevines have grown in ‘Khazandeh’ training system. In this system, the roots of the plants laid down in a trough (depth: 80 cm and width: 100cm), and the trunk is placed on a small mound formed after digging the streams. The experiment was carried out as randomized complete block design (RCBD) with split plot arrangement with five replications during 2015 and 2016 in vineyards of Shazand, Iran. Different amounts of potassium fertilizer in four levels 0, 0.75, 1.5 and 2.25 kg per vine in main plots and foliar application at three levels 0, 9 and 18 kg of magnesium sulfate salt per 1000 liters of water (In 2 stages after fruit set within 10 days) in sub-plots were used. In the second year of experiment natural frostbite occurs in 4th may 2016 and minimum of absolute temperature was 0˚C and wind speed was 6 m/s. In addition to the occurrence of natural frostbite, two artificial cold stages were applied on the buds of canes at temperatures of -3, -6, -9, and -12 ° C. According to the results, consumption 1.5 kg of potassium sulfate per vine with foliar 9 kg of magnesium sulfate salt per 1000 liters of water increasing tolerance of vines to artificial with the least electrolyte leakage and natural frostbite. The percent of sprouted buds in this treatment was 32% and ratio of potassium to magnesium ions was 5, indicating a balanced ratio between these two elements.