A five-year research project has been looking at what effect the timing of pruning has on tree growth and the size and quality of fruit in fruit-wall systems. The Gala orchard being used in the trial is a Galaxy clone on M9 and was planted in winter 2010.
Conventional winter hand-pruning has been compared with mechanical pruning at four different growth stages using a tractor-mounted mechanical cutter bar - pink bud, when extension growth has produced six, nine or 12 new leaves. As the trees have responded to the mechanically pruned treatments, more fruiting wood developed and the trees were better furnished, resulting in increased cropping in the narrower tree canopy. However, cumulative yields were still highest in the hand-pruned trees.
In strongly growing orchards, and where tree vigour control is important, it could be better to delay mechanical pruning to the nineor 12-leaf stage. Where limited regrowth and improved fruit bud formation are required, pruning at the nine-leaf stage appears to be best. Where trees are not vigorous and are in balance, pruning at pink bud may benefit fruit size and sugar content, but this will encourage more growth
Modern intensive orchards are already simpler and easier to prune than traditionally planted ones but it can still take up to 40 hours of labour per hectare. In fruit-wall orchards, mechanical pruning work rates are 1.5-2.5 hours per hectare, so even though some hand-pruning will be needed there is potential to save around £3,000 per hectare over an orchard's 15-year life.
Growers will need to weigh up the benefits of the increased cumulative yield from winter hand-pruning early in the life of a fruit wall against any labour savings from mechanical pruning.
For details on all AHDB Horticulture activity, see horticulture.ahdb.org.uk