A fruit tree has a bearing portion (foliage and fruiting buds) and a support portion (trunk and branchless leaders).
The smaller the size of the tree, the greater is the amount of the bearing portion to the support portion.
(cont from last issue)
In modern high-productive labour-saving orchard systems, tree canopies should be low and narrow, continuous and V-shaped, to allow maximum surface exposure with space between the rows for compact orchard equipment.
Because of its unique geometric shape and high canopy surface area per hectare, the Open-Tatura Ground-Level Production System has the potential to intercept around 70 percent of available PAR.
This means that by managing your trees from the ground, you do not need to compromise between yield efficiency and ease of working, harvesting and spraying.
Benefits of short trees
Research has shown that when light interception is constant, short trees have as great a capacity to bear and size a crop as do tall trees.
With a small tree, more of the space is devoted to bearing and less to support (non-bearing functions).
This aspect enhances orchard efficiency still further when combined with very high tree density and a simple tree structure (two leaders per tree with fruiting units and no branches).
Managing becomes much easier than with large trees, but it must be much more precise.
The efficiency of converting light energy into fruit is a measure of the efficiency of the orchard system to both produce carbohydrates from intercepted sunlight, called assimilation efficiency, and to partition the carbon to the fruit, called partitioning index.
In the long term, the conversion efficiency index incorporates the effects of sunlight on return bloom, fruit set, fruit size, and photosynthetic efficiency.
Measuring conversion efficiency
Experiments have been conducted in the USA measuring conversion efficiency of different tree training systems of apple trees independent of orchard factors such as planting density and light interception.
It was found that trees with V-shaped canopies had the highest conversion efficiency compared with Slender Spindle and Central Leader.
In these studies the V-shaped canopies intercepted about 70 per cent of available PAR, while the slender spindle system intercepted only 55 per cent of PAR in spite of 30 per cent greater tree density.
This illustrates the problem of short trees planted in single rows where light interception is relatively low due to a low ratio of tree height to clear alley.
The V-shape trees which fit conventional orchard equipment, had light interception levels similar to the English bed systems and Dutch multiple row slender spindle, neither of which could be maintained with conventional orchard equipment.
The high light interception of V-shaped canopies is the result of the canopy architecture which allows the tree canopies to grow partially over the tractor alleys.
See this article in Tree Fruit July 2023
This article is from the Orchard Manual: GROUND-LEVEL ORCHARD PRODUCTION
