When it comes to installing trellising, it’s best to adopt the “do it right, do it once” motto. With all the material available and growing systems out there, how do you, as a grower, know you’ve set your trellis properly?
This is the exact challenge a grower-driven research grant from the Washington Tree Fruit Research Commission sought to answer led by Mark De Kleine of De Kleine Machine Co., with Karen Lewis and Chuck Pezeshki of Washington State University, and Paul Booker P.E., of Steep Consulting.In an initial research study, the team discovered 90% of trellis failures occurred in orchards aged 10 years or younger.
“Of that 90%, something close to 80% of them were less than seven years old,” De Kleine, an agricultural and biological systems engineer, said. “That gives us a good idea that even with newer material, you can still have these failures.”
De Kleine said during this project, he visited an orchard where the grower didn’t adjust for the addition of shadecloth and the subsequent force of the wind.
“The trellis just snapped right off at the ground,” he says.
Trellising can fail in two way — through soil and through material failure. Understanding the soil is paramount, he says.
“Soil is the foundation for your trellis. Your soil is going to tell you if you have enough depth (strength) to embed a post correctly,” he says.
De Kleine says you need to know whether your soil profile is uniform or if you have layers. Different soil profiles impact how well your posts stay in the ground. Once your soil type is determined, the trellis can be designed with proper materials.
He cautions growers, though, trellis materials are not a place to take shortcuts. He says most failures were with trellis spacing of more than 40 feet apart with inadequate post sizing.
“There are so many areas in an operation to reduce costs” he says. “This is not the area to skimp on, for example: a piece of wood that maybe costs $5-10 more than another. When you’re talking about the difference between “span-feet for strength” in the realm of cost savings, that’s not a lot — that amount of money could be saved by calibrating sprayers annually.”
De Kleine says material failure can be technique-induced.
“I’ve seen a lot of trellis wires wrapped so tight around the wooden post that over time you can see that post start to collapse,” he says. “That wood is being compressed by that wire. Essentially, you’re losing the diameter of your post and that is another start to material fatigue, and material failure.”
Using the Trellis for Support
With the density of modern apple orchards getting tighter and tighter, the root structure of trees is changing, De Kleine says. Gone are the days when trees were self-supporting. Growers must rely more on the orchard infrastructure to support trees.
“In high density modern plantings, the root structures are becoming very, very small,” he says. “Essentially, you’re building that root structure above the ground, to support all of the load.”
De Kleine says the biggest need in trellising is a baseline when planning a new orchard system. The trouble with trying to develop a one-size-fits-all recommendation is variation from site to site – sometimes even within the same parcel.
“You can’t build the same trellis on a flat surface that you can on the side of a hill. It may look somewhat similar, and you can use the same materials, but there are factors that you have to consider when environment changes,” he says.
Drip irrigation, nets, and building a trellis for a smaller canopy — those are all things that can impact the success of a trellis, and they are often not considered as the trellis is being designed.
“There’s any number of ways to build a trellis but you have to consider all the variables in play. If you haven’t, that’s risky” he says.
Some growers may build a trellis with a specific canopy size in mind. However, he says once that canopy gets established and trees are growing well, a grower may decide to grow fruit above the trellis.
“If you didn’t consider that initially, there’s a whole bunch of weight in that added fruit, that added tree structure, and that added canopy that you’re asking your trellis to support,” he says.
A Costly Mistake
Trellis failures are costly and not just in the replacement of the trellis structure, but also in the replacement of trees and the lost income that would have been generated from those trees. De Kleine cites an example of losing an acre of trees, younger than 10 years old. He says to figure out how many bins that acre-block was netting.
“In an acre of trellis going down, say you’re getting $10,000 per acre. Now you have to go back and re-buy all that infrastructure, re-buy your 1,200 to 1,500 trees, plus eat the cost of that $10,000 — per year — until you’re back in production,” he says.
The cost, break in production, and loss of income adds up quickly. Leaving some specific variables unaccounted for is risky, which means losing capital.
“The reality for anybody who is growing fruit is the minute you lose the infrastructure you can go to the store and buy the poles, wire,” he says. “When you lose the trees, you’ve now started over.”
Some quick places for improvement, De Kleine says, are to look down your orchard rows for leaning posts.
“If you see posts leaning that means your soil, your foundation, is not adequate. If you see leaning posts, that’s your first indication you need to support your fruit better,” he says.
Another place for improvement, De Kleine says, is outside rows in the prevailing wind.
“They’re going to need more strength than other places. Consider strengthening outside rows — that’s an easy gain — there’s a lot of benefit to blocking wind,” he says.
Ask for Assistance
Mark De Kleine of De Kleine Machine Co. stresses the importance of professional help. He encourages growers to take an engineering approach to trellis design, so wind load, added canopy weight, irrigation, etc., can be factored into the design of the trellis.
“There’s a reason this is done with numbers, in the engineering world we can account for variance and we can see if you add this (specific) wind load, your post grows with it,” he says. “If you’re talking trellis and no one is mentioning these variables, consider an alternative.”
Above all, De Kleine says if you have questions, get help with trellising design. His website, Trellx.com, is a portal for growers to get help on design for trellises and protective cropping systems and access resources and models.
“As a business, weigh the risk of losing trees and production for a couple of years, versus correctly supporting the loads. It really comes out to be a fairly easy decision to use engineering models,” he says. “You want to do this once and then have good confidence that it’s going to hold up.”