To investigate the effect of four timings of mechanical pruning on yield and fruit quality compared to a hand pruned control in an intensive ‘Gala’ M9 orchard planted as a fruit wall

Abstract

The fruit wall (le mur fruitier) has generated much interest but differing recommendations from other regions in Europe regarding the optimum timing of the mechanical pruning has led to confusion among growers in the UK. In order to determine the effects of different times of pruning and provide growers with robust guidelines, a trial was established in 2012 in a 2-year-old ‘Gala’ (clone Galaxy) orchard planted on M9 at 3.5×0.5 m in the South-East of England. The timings of mechanical pruning were determined by growth stage: pink bud and when 6, 9 or 12 new leaves emerged on the current season’s growth, and these varied by up to 38 days between the different years in the trial. The control was pruned by hand in the dormant season. Half the plots received additional pruning during the dormant season to remove very strong or very weak growth between the trees (inter-tree pruning) in order to investigate whether reducing the branch density affected yields, fruit quality or size. The trial was designed as a fully randomised block consisting of 4 replicates of each treatment. In all years the length of extension growth was related to the time of pruning with later cuts generating the least extension growth. In the first 3 years the yields were greatest in the hand pruned plots but the differences in yield decreased over time. The cumulative yield was highest in the hand pruned control. In the first 2 seasons after the mechanical cuts were imposed, fruit size and sugar content were affected especially in the treatments applied later in the season. These differences reduced in the 3rd and 4th years of the trial. The effects on fruit size, colour and sugar content from inter-tree pruning were small and varied from season to season. Some small differences in fruit mineral content were observed in some years but these were inconsistent and only significant in one or two instances. Nitrogen content of leaves was lower in trees pruned at the two later growth stages. Some modest labour savings were achieved in the mechanically pruned plots.