Rotten wooden support posts have become quite an issue, replacement posts have been found to rot in as little as three years.
Post rot would seem to be quite a problem for anyone who uses wooden posts to support vineyard trellises. This problem is no doubt due to the EU ban on the principle chemical mixture that was used for many years to tanalise wooden posts. The chemical mixture used pre 2004 was called "Copper Chrome Arsenic" (CCA) this was banned for use in the UK in 2004. Replacement treatment chemicals have been tried, but unfortunately these do not seem to offer the long term protection of the CCA.
The posts typically rot within 150mm of where they go into the soil. Anything above this depth (or below) seems to survive very well. Many of the the posts in the original area of the vineyard are now rotting through at ground level.
The rot in the picture above is typical.
Unfortunately with the post's weakened a strong wind tends to bring down the row of vines.
In the picture below you can see many of the vertical posts leaning over. The (shiny) steel posts you can see in the picture (ready to go into place) are the replacement.
Galvanised steel posts have been selected as the replacement. Whilst more expensive than wooden posts this will be more than offset by the excellent service life they offer (at least 25 years)
The posts in use for replacement at Little Oak Vineyard have been supplied by Hadley Group. (see this link for their website: http://www.hadleygroup.com/vineposts.aspx)
One of the problems that has been faced at Little Oak Vineyard is the physical task of knocking new posts in. The gap between the rows of vines is too small for a tractor mounted post whacker to work. The old fashioned ways of using either a post awl or post rammer to hammer the top of the post takes at least ten minutes to knock a single post in to full depth and is very physically demanding.
A petrol driven auger does make things a little physically easier (and a better job overall than just knocking the post in by hand) but takes even longer (the extra time is taken to auger the hole in the soil before driving the post home with a post awl or post rammer). Even at a conservative time estimate of ten minutes per post to drive each post in manually (plus more time would be needed to set out the posts, replace the wire and refit the vines) replacing all of the posts with a human powered awl or post whacker would require at least 67 man hours work at Little Oak.
The metal posts go approximately double the distance of the wooden posts into the ground, that in itself creates even greater problems -
The post supplier suggested the use of a petrol driven post whacker. The only thing that can be said about this is WOW, what a fantastic bit of kit. It easily drives the post to full depth in the ground, taking about 45 seconds to drive the post to full depth, you simply put the unit onto the top of the post, squeeze the throttle and the machine drives the post in with no effort from you. The only physical effort is lifting the 15kg weight of the unit onto the top of the post. (to put that into perspective, the blue post rammer in the picture above
The video below shows the petrol driven post whacker in use -