Effect of Soil Removal Time from Buried Vine, Timing and Severity of Pruning on Reducing Spring Frost Damage in Vineyards in Cold Regions of Iran

Many vine growers in cold regions of Iran, in the ‘Khazandeh’ vine training system, for protecting vines from freezing in automn and winter, and frost in early spring, bury vines in the autumn and remove soil in mid-April, and postpone pruning until the flower structure appears in the end of May. The aim of this study was to investigate the best time for soil removal of buried vines, timing and severity of pruning of vines following exposure to spring frost to reducing frost damage. Two experiments were carried out in 2015 and 2016 in the cv. ‘Bidaneh Sefid’ vineyard of Javersian, Khondab, Iran. The first experiment was conducted in randomized complete block design with three treatments and six replications. Treatments included: T1: soil removal in 16 March, T2: soil removal 4 April and T3: soil removal in 24 April (control). The second experiment was carried out using randomized complete block design with 10 treatments and three replications. Each treatment was a combination of pruning time (19 March, 7 April and 27 April) and pruning severity based on the number of buds (4, 6 and 8 buds). In both experimentes, the vines experienced spring frost. In the first experiment, the best time for soil removal from buried vines was after 4 April. March 16 with lowest sprouted buds (%65) had the highest frost demage. In the second experiment, the number of cluster per sprouted buds (fertility coefficient) in short prunings (T2L1 and T3L1 with 50.5% and 48.9%, respectively) were significantly higher than the long pruning (T1L3 and T2L3 with 30.7% and 28.4%, respectively). On the other hand, T3L1 with 24.6 tonha-1 had the highest fruit yield. Considering the results of this study in the “Khazandeh” vine training system, when the vines are exposed to spring frost, to obtain a high sprouted buds (%), fertility coefficient and fruit yield, the best time for soil removal from buried vines and pruning is second half of April.