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Information - The FFC Bulletin - 2014 V4 October

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Tanalised post alternatives used in the national grape cultivar library-vineyard at the BHU

By Charles Merfield

Tanalised pine posts are a mainstay of New Zealand agriculture and are also widely used globally in agriculture and for many other purposes, e.g. buildings.  Although tanalised wood has been in use since the 1930’s and has been widely considered to be safe, there is growing concern about leaching from posts into the soil and wider environment, especially where posts are used in high densities, for example, vineyards, and orchards (e.g. see [1, 2]).  The tanalisation preservative is based on copper chromium arsenate (CCA, also called chromated copper arsenate), a chemical combination of three heavy metals (copper, chromium and arsenic) which are inherently toxic, and as chemical elements they cannot be broken down. 

There are also issues with disposing of tanalised timber at the end of its life: burning treated wood produces toxic compounds (the heavy metals being chemical elements cannot be destroyed), so treated wood should only be burnt in specialist facilities and the ash contains high levels of the metals so it must be disposed of correctly, typically in landfill.  Unburnt timber should also only be disposed of in properly managed landfill. 

In addition, the USA and Canadian government’s organic standards prohibit the use of tanalised posts, and a range of similar preservative treatments, so any organic producers wishing to export to North American markets cannot use treated posts.

Alternatives to tanalised posts are therefore becoming of increasing importance. 

In 2010, when the national grape cultivar library vineyard was being established at the BHU (see the 2013 V1 Bulletin article) the USA organic standards had just brought in the tanalised post ban.  As part of the work undertaken by Organics Aotearoa New Zealand (OANZ) identifying alternatives to tanalised posts (including the ‘Over the Fencepost’ booklet) the grape cultivar library vineyard was used as a demonstration site for a number of the non-tanalised post alternatives. 

The post collection is a demonstration rather than a trial, so no comparisons are being made among the different posts nor tests of their performance.  Also inclusion of any particular post is not an endorsement of that post by the BHU or FFC nor is the non-inclusion of any post a rejection of that post by the BHU or FFC. However, anyone is welcome to view and assess the posts for themselves during normal working hours.  The vineyard is sited at The BHU Farm, The Hort Research Area, Lincoln University.  Google map. You can also email This email address is being protected from spambots. You need JavaScript enabled to view it. for more information.

If you need specific information on what post treatments and alternatives are acceptable under USA USDA NOP rules, ATTRA have produced a pamphlet “Pressure-Treated Wood: Organic and Natural Alternatives".

Below is a list of the posts in the vineyard and recent photos that show the posts four years after establishment.

UltraPost (row 1), Industrial Tube Manufacturing Co Ltd


 

EcoPost (row 2), Industrial Tube Manufacturing Co Ltd

 

Wood Shield (row 9), Wood Shield Pty

 

Eco Trellis (rows 4, 5, 12 and 13), NZ Tube Mills

   

IR posts (rows 6 and 7), Integrated Recycling Ltd (AU) / Pukekohe Timber & Packaging (NZ)

  

Recycled Plastic Post (rows 9 and 10), Empak Distribution

 

Wallaba Posts (row 11), BBS Timber

  

References

1.    Clothier, B.E., Green, S.R., Vogeler, I., Greven, M.M., Agnew, R., van den Dijssel, C.W., Neal, S., Robinson, B.H., and Davidson, P., CCA transport in soil from treated-timber posts: Pattern dynamics from the local to regional scale. Hydrology & Earth System Sciences Discussions, 2006. 3: p. 2037-2061. http://www.kiwiscience.com/JournalArticles/HydrologyEarthSyst2006.pdf

2.    Greven, M., Green , S., Robinson , B., Clothier, B., Vogeler , I., Agnew, R., Neal, S., and Sivakumaran, S., The impact of CCA-treated posts in vineyards on soil and ground water. Water Science & Technology, 2007. 56(2): p. 161–168. http://www.iwaponline.com/wst/05602/wst056020161.htm


 

 

Botanical Name

Maori/European Name

Flammability class

Kunzea ericoides

kanuka

High

Leptospermum

scoparium manuka

High

Cyathea and Dicksonia spp.

tree ferns

Moderate/High

Cyathodes fasciculata

mingimingi

Moderate/High

Dodonea viscosa

ake ake

Moderate/High

Phormium cookianum and P. tenax

flax/harakeke

Moderate/High

Podocarpus totara

totara

Moderate/High

Agathis australis

kauri

Moderate

Beilschmiedia

tawa tawa

Moderate

Dacrydium cupressinum

rimu

Moderate

Metrosideros umbellata

southern rata

Moderate

Pittosporum tenuifolium

kohuhu

Moderate

Podocarpus dacrydioides

kahikatea/white pine

Moderate

Weinmannia silvicola

tawhero/towhai

Moderate

Aristotelia serrata

makomako/wineberry

Low/Moderate

Cordyline australis

ti kouka/cabbage tree

Low/Moderate

Coriaria arborea

tutu

Low/Moderate

Hebe salicifolia and H. stricta

koromiko

Low/Moderate

Hoheria spp.

houhere/hoheria/lacebark

Low/Moderate

Knightia excelsa

rewarewa

Low/Moderate

Melicytus lanceolatus

mahoe wao

Low/Moderate

Melicytus ramiflorus

mahoe/whiteywood

Low/Moderate

Myoporum laetum

ngaio

Low/Moderate

Nothofagus menziesii

tawhai/silver beech

Low/Moderate

Phyllocladus glaucus

toatoa

Low/Moderate

Pittosporum crassifolium

karo

Low/Moderate

Pittosporum eugenioides

tarata/lemonwood

Low/Moderate

Plagianthus regius

manatu/ribbonwood

Low/Moderate

Weinmannia racemosa

kamahi

Low/Moderate

Carpodetus serratus

putaputaweta

Low

Coprosma grandifolia

raurekau, kanono

Low

Coprosma repens

taupata

Low

Coprosma robusta

karamu

Low

Corynocarpus laevigatus

karaka

Low

Fuchsia excorticata

kotukutuku/fuchsia

Low

Geniostoma ligustrifolium

hangehange

Low

Griselinia littoralis

papauma/broadleaf

Low

Griselinia lucida

puka

Low

Macropiper excelsum

kawakawa/pepper tree

Low

Psuedopanax arboreum

five finger

Low

Pseudopanax crassifolius

horoeke/lancewood

Low

Solanum aviculare

poroporo

Low

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