PECULIARITIES IN THE INITIAL STAGES OF DEVELOPMENT FOR SOME FRUIT TREES, DEPENDING ON THE TEMPERATURE CONDITIONS

Abstract

The last decade has been characterized by an increased frequency of climatic anomalies and their amplitude. These anomalies affect the productivity of crops and orchards, which is directly dependent on agro-meteorological conditions. The registered tendencies to change the hydrothermal conditions in the different regions of the country sometimes are a risk factor for their productivity, especially in the initial phenological stages of the development of the fruit trees. Bud dormancy on the fruit trees from the temperate zones is a phase of development that occurs annually and enables trees to survive cold winters. To estimate the chill requirements of orchards, besides temperature data, three chronological dates must be defined: the chill accumulation start date, the deep dormancy breaking date, and the date of eco dormancy end. This study aims to assess the thermal conditions in the initial stages of development of some stone fruit plants grown in Bulgaria. There were analyzed the conditions during the deep dormancy in the orchards and the permanent transition of the average daily temperature above 5�C. Chilling requirements for breaking dormancy were studied for some peach, cherry, and apricot cultivars, located in the regions for industrial producing of these plants. The Utah chilling unit model was used to measure the accumulation of chilling requirements.