Prediction of blossoming of apple tree (Malus domestica Borkh) BY phenological models

Abstract

Paper discusses the possibilities for predicting date of blossom of apple tree (Malus domestica Borkh) cv. ‘Bobovec’ in Ljubljana.. The study was conducted at the University of Ljubljana, based on phenological observations made by Hydrometeorological institute of Slovenia during the period from 1967 to 1996. Four types of models are shown. Firstly, the model based on accumulated heat expressed  in degree-days (DD) is presented. Secondly, models based on linear multiple regression methods (including input parameters (a) phenological data of autochtonous plants, (b) timing of earlier phenophases of the same fruit tree and (c) environmental parameters) are compared and discussed. The date of flowering is strongly correlated with the time of earlier phenophases of various species: first leaves unfolding and beginning of flowering. The time for first leaves unfolding of birch (Betula pendula Roth) and  linden (Tilia platyphyllos Scop.) were important for flowering of apple, so were the mean March and April air temperatures. The analysis showed that a complex relationship exists between the timing of phenophase occurrence and environmental conditions.