Shoot growth on young Smitten trees with different crop loads

2019-03-19 | Stephen Tancred | Future Orchards® trial report, Stanthorpe, Queensland

This Stanthorpe trial investigated how crop load affects vegetative growth in young Smitten apple trees that had not yet filled their allotted canopy. Trees on M26 rootstocks, planted at 3.4 m by 0.4 m and trained to two leaders, were compared under three crop-load treatments: no hand thinning, thinning to eight apples per leader, or complete crop removal.

The trial also compared two winter pruning methods – cutting lateral shoots with secateurs and manually breaking them – but found no consistent differences between those pruning treatments. Crop load had a much clearer effect. Partially thinned trees produced leaders about 14 per cent longer than unthinned trees, while complete fruit removal increased leader length by about 23 per cent.

Importantly, removing all fruit produced only about a further 9 per cent leader-length increase over partial thinning. The report therefore concludes that retaining eight apples per leader, approximately 16 apples per tree and around 20 t/ha, could provide a better commercial balance between obtaining a crop and still achieving useful canopy growth.

Thinning also increased lateral shoot growth, but the very close planting meant extremely long laterals were not required. The work supports the principle that young orchards can carry some crop while still building canopy, provided crop load is deliberately restricted.