and light penetration is improved, resulting in better quality fruit. Labour costs are also reduced and pruning, training and thinning is made simpler.
Ultimately, orchards are managed as ‘fruiting walls’ making harvest easier as well, especially since it allows for increased automation and
mechanization, enhancing productivity, quality and efficiency.
Tannant recommends growers use 12-foot pressure-treated posts that are at least four inches in diameter and go at least three feet into the ground. “Although it’s sometimes difficult to get the posts three feet into the ground, it is important because the ground strengthens the post and helps prevent it from tipping over,” he explained. The top wire (12.5 gauge, high-tensile, class 3 galvanized wire) should be nine feet above the ground, allowing the top foliage to grow to 10 feet or so. The lowest wire should be three feet above the ground, and the three other wires should be two feet from each other, with a little less space before the top one, if necessary.
Posts should be 30 feet apart; closer
on hilly ground.
To ensure quality, CSA 080 posts should be used. “The rot zone at ground level is where the hardest bending and the highest loads are. Rot is not visually detectable at first, but it can result in an 80 per cent loss in strength,” he warned.
With normal weather, that quality of post should last for 25 years with occasional exposure to rain. He noted that a four-inch post has 75 per cent more strength than a three-inch post, and a six-inch post is even stronger. Most important, is design of the end- post bracing structure.
Larger posts should be used there, so for the H-system, six-inch diameter posts, 14 feet long are recommended, and they should go four feet into the ground, with an eight-foot minimum brace between the two end posts, 54 inches above the ground.
A double high-tensile wire should then be installed between the brace at the second post, at a maximum angle of 25 degrees, so it is attached to the end post six inches above the ground, with 500 pounds of tension. A four-foot brace is no good as it doesn’t give you the best angle for that angled support wire, he added.
Alternatively, Tannant says a better system is to use a three-foot deep soil anchor, placed eight feet from the end post at a 30 degree angle, or less, attached to the end post 54 inches above the ground.
The post could be on a 10 per cent or six-inch angle outwards from the trellis and there could be 2,000 pounds of load on the wire.
Growers were excited about another suggestion from Tannant, that instead of having to deal with the problem of wires sticking out eight feet beyond the end of each row, where the tractor is constantly turning or people are trying to walk by the end of the row—instead, add another post beyond the end-post, using up bits of leftover wire, 20 feet away.
“That way, you gain trees and remove a hazard,” he advised.
Once the trellis system has been installed and trees planted, the work is not done.
Regular maintenance is needed to ensure the correct tension is maintained on the wires, so each spring, before the trees get loaded with fruit, growers need to snug wires, tighten any that have loosened and tweak the system to make sure there are no weak points.
British Columbia FRUIT GROWER • Summer 2018
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