In theory, trellis rows could be “as long as you want them to be,” but in
reality there are almost certainly limits to the amount of tension the
end-posts can handle without coming out of the ground.
Consider the worst case scenario: Trees that have grown to 3-ft above the wire
(i.e., 13 ft tall) with 2000 bushels/A evenly distributed over the upper 12 ft
of the canopy (i.e., none within 1 ft of the ground). That could mean that 25%
of the fruit are above the 10-ft top wire, and in my experience those upper
limbs will tend to fall toward the leeward side of the tree due to wind
effects. Let’s assume that trees are on 10-ft row spacings and that 10% of the
total crop is above the wire and off-center to the leeward side. If I’ve done
the math correctly so far, that means that every acre will have 4-tons of
apples off-center and at least 10-ft above ground. At 10-ft between rows, it
will require 4,356 ft to make an acre. Thus, with rows 1000-ft long, there
will be roughly 1 ton of off-center apples 10-ft above the ground. Now add a
40 mph crosswind just before harvest, and (for those in the east) assume that
you just had 10 inches of rain due to a hurricane coming up the coast. The line
posts will provide some support, but ultimately the greatest stress will be on
the end-posts, and that stress will increase with the total length of the
trellis.
Even on short rows of only 300 ft, I have gradually seen trellises go
off-center with time (i.e., line posts begin to lean a bit) due to wind
effects, uneven cropping on the two sides of the trees, and slope (which leads
to uneven frost-heave effects). If the trellises are tilted just a bit under
the scenarios outlined above, then the stresses on the end posts will be
multiplied. Admittedly, my observations are mostly with wider trees and wider
row spacings, and those planting systems probably was more prone to going
off-center than a narrow tree wall. Nevertheless, the side-ways forces on
trellises should not be ignored.
You may quibble with some of my assumptions, but I really would like to
see/hear an engineers perspective on how long rows can be given various soil
types, diameter of both line posts and end posts, crop distribution in tops of
trees, soil moisture levels, etc. Whatever the answers might be, I can
guarantee that when a trellis goes over in a storm, the owner with shorter
sections is likely to come out with smaller losses than the person with longer
runs if one assumes that construction on shorter and longer sections was
equivalent.
****************************************************************
Dave Rosenberger, Plant Pathologist (retired)
Cornell's Hudson Valley Lab, P.O. Box 727, Highland, NY 12528
Office: 845-691-7231 Cell: 845-594-3060
http://pppmb.cals.cornell.edu/people/dave-rosenberger
****************************************************************
On Feb 20, 2014, at 12:43 PM, Hugh Thomas
<[email protected]<mailto:[email protected]>> wrote:
Seems to me, that they could basically be as long as you want them to be. I
would calculate the fuel capacity of my tractors so that one doesn't run out of
fuel before getting back...
On Thu, Feb 20, 2014 at 7:27 AM, Fleming, William
<[email protected]<mailto:[email protected]>> wrote:
We had rows 2200 feet long between end anchors. 4 wires, 10’ high with posts
spaced at 42’, 3’ deep. End posts were a larger diameter, 4’ deep at about a
45° angle.
Wires and anchors were attached to a 4’ long screw in steel anchor with 8”
plate. Ground was basically flat.
No problems holding a bumper crop.
Bill Fleming
Montana State University
Western Ag Research Center
580 Quast Lane
Corvallis, MT 59828
From:
[email protected]<mailto:[email protected]>
[mailto:[email protected]<mailto:[email protected]>]
On Behalf Of Arthur Kelly
Sent: Thursday, February 20, 2014 6:24 AM
To: Apple-Crop
Subject: [apple-crop] Tall spindle trellis
What is the longest length of trellis for tall spindle apple planting that
growers have experience with?
--
Art Kelly
Kelly Orchards
Acton, ME
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