The chilling requirement is the most important factor in the awakening of the trees and the beginning of the swelling of the buds in pistachios. It is necessary to know the chilling requirement in order to determine the suitability of a variety for cultivation in a specific area and outside the native areas of cultivation, to determine the timing of horticultural operations such as foliar spraying according to the time of tree emergence and the specific phenological stage faced with the phenomenon. To carry out this research, the phenological stages of four varieties of Akbari, Kale Qouchi, Ahmad Aghaei and Fandghi were recorded during the crop years 1397-1398 to 1399-1400 in the towns of Kerman, Anar, Zarand, Rafsanjan, Sirjan and Shahrbabak of Kerman Province. The cold was calculated in different ways. According to the calculations, more homogeneity and less variability were observed in the bud swelling stage of the dynamic model compared to the Utah model and cold hours, and this phenological stage in the dynamic method has a constant cold unit amount, while the other two models are added. Therefore, using the dynamic model, it is possible to better predict the germination time of pistachio in Kerman province. The data analysis also showed that there is the highest correlation between the capital requirement obtained by the dynamic method and the start date of the germination stage. Ahmad Aghaei cultivar with 59 units, Kale Ghochi and Fandagi cultivars with 58 units and Akbari cultivar with 55 cold units enter the bud swelling stage dynamically. Bud swelling in pistachio varies according to cultivar, climatic characteristics and topography of each region.
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