Monday, 09 November 2015 07:00

Durable posts

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One of the species that is showing promise here in New Zealand is E. bosistoana, also known as coastal grey box. One of the species that is showing promise here in New Zealand is E. bosistoana, also known as coastal grey box.

Vineyard owners and wine companies are being encouraged to start planting specific eucalypt species , that could produce durable hardwood posts in the future.

It may be something of a novel idea here in New Zealand, but as Paul Millen from the NZ Drylands Forest Initiative (NZDFI) says, eucalypt hardwood has a long history of use in vineyards throughout Australia.

Wood durability is what makes the NZDFI's species special. Unlike treated pine which makes up the majority of New Zealand's current vineyard posts, their hardwood doesn't need treating to be placed in the ground.

Millen who addressed the recent Organic Winegrowers Conference, says it was brought to his attention back in 2003, that treated Pinus radiata was causing some issues for growers throughout the country. A Marlborough grape grower questioned whether there were any durable timbers available that could be used instead. It got him thinking and researching. What he came up with was the well-known eucalypts. Not only were they fast growing, they also produce very strong timber due to their density and produce natural chemicals that made them durable in the ground.

"I travelled to Australia and discovered that historically all the vineyards there were supported by eucalyptus posts of one sort or another. Some of those posts have been in the ground for more than 50 years."

Eucalypts are not unknown on this side of the Tasman either, with small tracts of them often grown on rural properties. Millen managed to track down a few small blocks in Marlborough and went about testing his theory that they would be suitable for vineyards. That was back in 2005, the very first eucalypt posts, untreated, are still standing sentinel to Millen's vision.

While it might seem like an easy proposition to chop down the few old trees scattering the rural landscape, Millen quickly realised much more research was required. For example there are over 600 species of eucalypt, yet probably less than 30 may grow in New Zealand conditions and produce durable timber.

"You can't just grab any sort of gum tree and think it will do the job," he says.

For just like grape varieties, different eucalypts species require different growing conditions to thrive.

So began a $2.6 million breeding programme that has allowed the NZDFI to trial a variety of species, in a number of different sites.

"Since 2008 we have planted over 140,000 trees, across 26 different sites. We have something like 45 trials going on within those sites,"

The project also has five NZ School of Forestry PhD students based at Canterbury University, working solely on the NZDFI's research programme. Millen says they are vital to the success of the project.

Paul-Millen"There has been little research of heartwood forms and why some species create heartwood with cellular extractives that make the wood durable. That is what the team at the University are doing now. Our vision is to be a world leader in breeding ground durable eucalypts, and we are actually there already."

Funding from MBEI, announced earlier this year means the project can grow even further.

"We are part of a forest industry and MBIE partnership for the next seven years. We plan to roll out selection and outcrossing to improve growth, form, wood quality and pest resistance of the species," Millen says. "We want growers to match the species to sites as well as apply innovative management and silviculture systems."

While they are fast growing, Millen says there is still a lot to learn before wide spread eucalypt posts are available for growers.

"The challenge is that every site is going to vary in terms of growth rate, so you can't lock in a time frame. We don't know enough yet to say we can grow a crop of posts in say 12 or 15 years. But that is where our research will help us."

As for growers taking matters into their own hands, Millen is all for it.

"Growers need to be planting their own trees now. You don't want to grow the trees right on the vineyard, because there are issues with that. But growers should be getting in with farmers or forestry and look at planting out now. I have an ex grape grower who has bought land out near the Rai Valley (Marlborough) and he is planting a 60 hectare block this year. That is a smart thing to do."

Despite the wine industry being the initial motivator, Millen says there are many other potential uses for the hardwood.

"For example," he says, "cross arms for New Zealand's electricity networks. Sleepers for rail networks, wharf timbers for ports and marinas, residential and commercial high strength LVL beams and finishing timbers and decking and outdoor furniture."

With tropical rainforest hardwood getting harder to come by, Millen's project could end up being a nice export earner for New Zealand in the future.

The NZDFI was this year's Supreme winner of the Cawthron Marlborough Environment Awards.

 

The cost of broken posts

Every year, between three and five percent of a vineyard's timber posts are damaged by tractors, harvesters and mechanical pruners. The cost to the industry is thought to be in the millions.

Millen says in Marlborough alone, more than half a million timber posts need replacing every year.

Marlborough with say 25,000 hectares of vines

Approximately 600 posts per hectare

Total existing posts equals 15 million

Potential replacement if 3% of those posts are damaged is 450,00 posts a year

Potential replacement if 5% is damaged, is 750,000 posts per year.

Adding to that cost scenario, is what do you do with those damaged posts. If those posts have undergone treatment, then they become a health hazard to burn or dump.

Durable eucalypts require no treatment, they are three times stronger than a pine post and can last in the ground for decades.

For more information on the NZDFI, visit their website; www.nzdfi.org.nz

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