Truffles, mushrooms and mycorrhizas
© Truffles and Mushrooms (Consulting) Ltd                     
Selecting a suitable location for growing an edible mycorrhizal mushroom
Selecting a suitable location for cultivating an edible mycorrhizal mushroom
Climate, choice of host plant, and soil chemistry, texture, drainage and organic matter content will all contribute to the success of a plantation established to cultivate an edible mycorrhizal mushroom.  For some of the truffles and a few other edible mycorrhizal mushrooms we have some idea of their ecological requirements but for the vast majority of the 1000 plus species we don’t have a clue.  Between these extremes are species like porcini and chanterelle where we have some information available but have yet to learn how they might be cultivated.

In the attached table (143 KB pdf file) are rough comparisons of the climate in centres adjacent to natural and artificial Périgord black, Burgundy, Italian white and bianchetto truffle truffières.  From this it can be deduced what species of truffle might suit other locations.

All of the European truffles require a relatively high pH soil.  Naturally high pH soils are common in Europe and found in areas where there is much limestone - a vertical section of a soil developed over limestone is shown to the bottom left.  Work over the past 30 years foremost in New Zealand, and in other Southern Hemisphere countries, has shown that a high soil pH can be created artificially simply by mixing large amounts of lime with a soil.  So the first step is checking the suitability of a site is to analyse soil samples to determine if the soil is suitable in its natural state, if it can be modified, and if there are any other issues that might cause problems after planting.  

Soil sampling
You need to collect a soil sample from the soil surface down to 25 cm. One of the simplest methods I have found, particularly in compacted soil, is to use a 25 mm (1") diameter and 30 cm long drill bit in a rechargeable electric drill with a large enough chuck - usually 10 or 12 mm diameter. The tape on the drill bit is to mark the 25 cm depth. Before you start you should first remove any vegetation but do not remove any of the surface soil – a pair of hedge trimmers can be useful. Don't use a dirty or oil-covered drill bit or one that is painted - the paint might contain substances that could upset the soil analyses.  If you don't have a drill and bit, a soil auger can be used.  Alternatively a trowel will do, although in compacted soils you may first need to dig 25 cm deep holes with a spade and then shave a layer off the side of each hole using your trowel.  Try not to bias your sample with the more easily accessible topsoil.  Take samples from at least 20 spots around the block avoiding soil around water troughs, gates, headlands, dung or urine patches, stock camps, abnormally wet or dry spots, or other areas likely to have abnormal fertility.  Put the samples from each of the 20 holes into a clean plastic bucket.  When you have taken all 20 samples thoroughly mix the soil in the bucket and put at least half a kilogram into a labelled, thick-walled, zip-lock polythene bag.  Seal the bag.  If the area to be planted is quite large (more than a hectare) and the soil changes across it, the area should be divided into sections that appear similar and the above procedure carried out for each section.

In natural truffle soils the pH of the subsoil usually increases with depth as you get closer to the parent rock.  Similarly a layer of acidic volcanic ash or loess may have been deposited over the top of the limestone in the distant past so that the pH of the soil reflects this acidic layer rather than the underlying limestone.  In these situations and others where the soil changes with depth it is important to sample and analyse both the topsoil and the subsoil.  Consequently, two bags of soil are needed - one from between 0 and 12 cm and the other from between 12 and 25 cm.

Print off a copy of the next page and fill in your details and put it with your samples in a cardboard box or robust plastic mailer bag.  Please include a map showing the location of your property, a note about the drainage characteristics of your land, the name of your soil type if you know it, and anything else that may help us.  Then within 24 hours of sampling send either by Courier Post (only available through New Zealand Post Shops) or Fastpost to: Dr Ian Hall, Truffles and Mushrooms (Consulting) Ltd, P.O. Box 268, Dunedin 9054, New Zealand.
A section of a rendzina soil developed over limestone.  
Often there are pieces of  limestone in the topsoil.