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Digging the Good Dirt on Soil Bugs

Wednesday, October 07, 2015, Denis Hocking's blog

Volunteers Wanted: Scion soil scientist Simeon Smaill is looking for volunteers to help with a series of trials he is running around the country.  He is looking at the effect of different nursery practises on early tree performance in the forest.

Background:  Simeon gave a very good background talk on this work to a small group of MDFFA members on Friday 15th, Sept.  Much of the talk was on the all important interactions between trees and the mycorrhizal fungi that live in association with them, assisting in the uptake of key nutrients. Without appropriate mycorrhizal fungi most trees just fail to grow, yet very little consideration has been given to managing or protecting these key players in the nursery. There are also other microbes that affect stress responses, including drought.

There has been little change in nursery practise since the 1980s, when it was felt that they had the systems to meet customer specifications for seedlings regarding height, diameter and root development. But there has been little consideration of the effects of nursery practise on subsequent tree performance in the forest. And it is known that the fungicides and soluble fertilizers used, often heavily, in the nursery adversely affect the beneficial soil microbes.

There are five common species of mycorrhizal  fungi found in nurseries, and although there are 20 or more other species that can "infect" radiate pine, Simeon says getting them into nursery stock will be difficult without a clear niche being available. Fungi not only have to battle fungicides and fertilizer, it is also open warfare between different fungi. Unfortunately the best mycorrhizal fungi are also the most sensitive to fungicides and fertilizers and hence the logic in assessing nursery practise effects on early forest performance. . 

Simeon says there are four key areas being examined in nursery practise:

  1. Physical management:  This includes stocking rates in the seedling beds and its effects on root development, nutrient levels, topping and undercutting of seedlings.
  2. Microbial interactions including the mycorrhizal and growth promoting microbes that improve nutrient uptake, stress tolerance and growth rates. There is also the possibility of using "friendly" microbes, notably Trichoderma spp., to compete with pathogens.
  3. Chemical management including fertilizers and fungicides, but also the possibilities of using plant hormones to produce fatter rather than taller seedlings.
  4. Tree genetics. Everything is treated the same in the nursery but different genotypes do vary in growth rate, stress responses and also their ability to recruit useful microbes.

Early work has already shown that the effects of nursery practise can influence forest performance for at least five years, covering the vital period when seedlings are competing with weeds.

Simeon is now looking for a wider range of different sites to conduct trials starting in 2016. These would only involve 180 trees, (3 replicates of 3 treatments, with 20 trees in each replicate) and Simeon wants as wide a range of soils, climate and other conditions as possible. Interested planters can contact Simeon at, 03 364 2949 ext. 7833, or 0212 666 305.  Alternatively contact Denis Hocking on or 06 322 1254

Further to this item, it is worth noting that our nurseryman and MDFFA Vice-President, Patrick Murray is to the fore in this work.  He is one of the new generation of nurserymen working on the next step, not least his work on redesigning seeder drums.

Soil microbe/plant interactions are becoming a hot topic internationally and there is a very good, readable, review in a recent copy of Science, (vol 349, pp. 680-83, 14/8/2015). There is a lot more going on down there than I ever realised. If you would like a copy contact me.

Denis Hocking

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Disclaimer: Personal views expressed in this blog are those of the writers and do not necessarily represent those of the NZ Farm Forestry Association.

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