Train your trees for the future

Tree architecture and training systems of yesterday, today, and tomorrow. By Grethe Bestbier.

If the orchard is seen as a jigsaw puzzle, then tree architecture is the most important piece. According to Dr Alberto Dorigoni, pomologist at the Edmund Mach Foundation in Italy, changing the tree architecture can affect all the other pieces of the puzzle. Various systems of tree training are seen all over the world. The question is, which of these systems is most suitable for the future?

Tall spindle and solaxe training is the traditional way of doing things. The typical spindle or solaxe training system is based on a single vertical or central leader and some secondary structural branches that are not cut back — this is called long pruning. Structural and permanent wood is often unproductive, serving only to redirect energy from the rootstock and tree outwards. The result is a three-dimensionally shaped tree, with strong peripheral and lateral structure.

Spindle and solaxe training gives good yields and quality, but has a few drawbacks. Pruning spindles is labour-intensive and demands high-level skills. It also requires spacing of four metres or more between rows, and time-consuming bending and spur pruning.

“Another major problem is that you need to thin very aggressively,” Dorigoni added. “This is difficult when trees are pruned long. Even harvest is complex. The complex secondary structures make almost any form of mechanisation impossible.”

Going 2D: the vertical multiple-leader training system

There are different ways of obtaining a two-dimensional tree structure. The most natural is a multi-leader trained structure that exploits the tendency of the tree to grow vertically. This structure consists of two or more permanent vertical leaders and short branches. Mechanisation and lack of skilled labour are favouring these narrower canopy systems.

Dorigoni pointed out that having two leaders divides the volume of the tree and creates new exposed surface. “The ratio of surface to volume is increased,” he said. Greater surface area improves light distribution and reduces shading. In terms of vigour, increasing the number of leaders creates an effect similar to that of a dwarfing rootstock — every added leader causes a reduction in trunk cross-sectional area.

“The number of leaders is an additional variable when we want to choose the right spacing and planting for a given area,” said Dorigoni, “besides the cultivar and the rootstock.”

Up to eight leaders can be used on vigorous rootstocks and still form a narrow canopy. Narrow canopies don’t block the passage between rows in the same way as the secondary structures on spindle and solaxe systems.

The future: Guyot systems and ultra-narrow training

According to Dorigoni, the last step in the evolution of the multi-leader is the Guyot system. The main differences between Guyot and vertical leader training are that, in the Guyot system, the vertical leaders become horizontal, the horizontal branches become vertical and semi-permanent, and there is no further important structure.

There are several benefits to Guyot systems. Removing long and lateral secondary structures allows:

• Better light distribution: Trees remain very flat throughout their lives. Since the crop is uniformly distributed, the fruit experience a better and more even light exposure.
• Mechanisation: Guyot systems facilitate mechanisation and allow transition towards SLIM — Small Light Manageable Intelligent — mechanisation.
• Easy visualisation of fruit: The fruit can easily be seen and removed from the tree. According to Dorigoni, about 95% of fruit are easily spotted without putting a hand on the tree or lifting branches.
• High-efficiency precision horticulture: With a Guyot system, the flat-canopy multiple-leader trees make it possible to calculate exact tonnage. This cannot be done with three-dimensionally shaped trees.
• Harvesting efficiency: The Guyot system offers an impressive harvest speed, easily reaching 300 kilograms per hour per person without expensive machinery.
• Crop protection: “Guyot revolutionises crop protection altogether,” said Dorigoni. “You need less water, pressure and ventilation.”
• Tree rejuvenation: With Guyot systems, replacement of strong vertical branches is possible for the entire life of the orchard.
• Optimal canopy structure: Even though V-shaped Tatura structures are highly productive, they impede mechanisation. According to Dorigoni, vertical Guyot systems can be planted in double rows, which is better from a mechanical and management point of view.

Image: The Guyot system in action: Pink Lady photographed 15 days after mechanical leaf removal.

Supplied by Alberto Dorigoni | Azienda S. Giusto of Dorigoni Brothers.