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Farming Truffles

By David Hunter

Quietly, and without too much fanfare, a small but growing number of farmers are looking at the option of growing truffles. In fact, in many cases, the farmers are not just being quiet about it, they are being highly secretive. The reason for this is that truffles have an extremely high value - usually in the multiple thousands of dollars per kg. In France and Italy where truffles have been wild harvested for centuries, the locals are secretive about the location of their truffle beds. So don’t expect to see too many ‘X marks-the-spot’ maps of the location of truffle farms.

Truffles are fungi that grow alongside, and in close association with, the roots of certain trees, usually oaks and hazels. The appealing edible truffles, especially the Perigold black truffle, (Tuber Melanosporum) are rare and valuable.

There is a report that a Japanese businessman paid $18,000kg for truffles in the 1990’s. The average price currently paid in Europe is in the range of $3000 to $5000 per kg. Truffles are not eaten in the same way as meat or vegetables they are used in the cooking process, finely slivered, to enhance taste.

While consumption of truffles is not a part of the mainstream Australian diet, it certainly forms a highly valued part of the cuisine of certain European regions. It is the most expensive food on the planet.

Truffles are seasonal - being harvested in winter - and they are most prized when fresh. In traditional European cuisine, therefore, there has been an on-season and an off-season for truffles and this means that the opportunity exists for Australian farmers to supply truffles in the European off-season.

Based in Bombala, NSW, Bill and Raylene Stevenson own and operate Australia’s only truffle nursery, and use technology developed in New Zealand. The technology is used under a licence from the NZ based owner of the intellectual property. Large parts of the technology are commercially confidential and so tech-nical details are limited.

There are native truffles in the Australian landscape but they are not palatable and have no market value.

The prospective farmer needs to set up a grove of trees at the right planting density and in the right conditions for the root zones of the trees to overlap. This creates the conditions for the fungi to live in the ground also occupied by the root mat of the trees. The truffle bed thus created is referred to as a truffiere (pronounced troo-fee-air).

The recommended planting density is around 450 - 500 trees per ha and other features of the selected site include:-

High pH soils.
The ground for the truffiere must be high in pH. Raylene comments, “This is really critical. A minimum pH level is 7.5 and the optimum is 7.9. Many of Australia’s farming lands are well below this level and, if a farmer seeks to establish a truffiere on low pH soil he/she must make the effort to lift the pH and keep it permanently high. The best course is to find a part of the property where pH is naturally high or, if you are serious about truffle farming, to move to a location where the soil pH is naturally high.”

Free draining soils. The development of the fungi is inhibited in clay soils. If the soil becomes too wet the fungi can also rot underground before it is ready for harvest. In order to develop the truffle bed the top 300mm of soil should be loose enough to enable the farmer to dig out the truffles when they develop.

Quality water/irrigation.
Irrigation water must be available to the site when required. Although the site need not be irrigated all the time, the fungi develops poorly if the ground dries out for too long. Supplementary irrigation is therefore required and the farm management plan must be hands on to the extent that soil humidity is measured regularly and not left to chance. Raylene states, “The guiding rule with irrigation is that, if the trees do it hard, the truffles do it hard. This means that the water source must not only be plentiful and reliable, it must be of high quality. There are times in our nursery operation we use a reverse osmosis treatment of water to ensure its highest quality.”

Ground selection. Truffles are sensitive to picking up chemical residues in the soil. Ground selection for the truffle site should take into account the previous land use and stay away from old drenching sites or cropping areas which may contain herbicide or pesti-cide residues. One of the potential advantages Aust-ralia has over European truffles is that the growing conditions here are cleaner and greener than in many European sites which have suffered the effects of acid rain and the results of industrialisation.

Trees. The most common trees supplied in Australia are European - English Oak (Quuercus Robur) and Common Hazel (Corylus Avellana). When these trees come from the nursery, they have already been treated in a way which will ensure the growth of the fungi. The Oak and Hazel trees create the best conditions for the Perigold Black Truffle.

Wind protection. The small trees need some form of wind protection when they are still young. However, this is not necessarily achieved by native tree belts because these can contaminate the truffle bed with wild truffle species.

Fencing. In the early stages of truffle bed development the young trees are vulnerable to rabbits and various other wild life. A fine fence is required to keep out all small grazing animals.

Buffer zone. Due to the potential for fungal contamination it is best to create a border-zone around the truffle bed. This may be in the range of 50m - 100m.

Climate.
A climate with crisp frosty winter mornings and plentiful sunshine hours is ideal. The Bombala region is suitable with the following characteristics; annual average rainfall - 649mm, mean daily temperature in summer - 20.5˚C, annual sunshine hours 2370, summer sunshine hours - 1579 (October to March). The need for irrigation becomes more pressing where summer temperatures are hot and dry.

Need for a truffle dog. Although a prototype electronic truffle sniffer is under development, the most effective method of truffle detection is with animals. Traditionally, in France, pigs have been used for this purpose but, in Australia, the favoured animal is a truffle dog. These dogs are trained to sniff the truffles to a depth of around 30cm and are rewarded with a treat - not a truffle - each time they locate the prize. Once located, the task still remains for the farmer to dig carefully with a pronged fork to recover the harvest. The need for digging is also a reason why the ground needs to be soft.

Time to harvest
. The complicated root matting and fungi development takes a long time to develop. First harvest in a truffiere may be from four to seven years after planting.

Yield. The yield of a truffiere is measured in kg’s of truffles per tree. Once the trees are mature, each tree has the potential to produce up to 1kg of truffles per year. This is a reasonable planning figure. There have been cases of trees yielding up to 2kg per year.

Growing/Harvest cycle.
The European trees are deciduous. They emerge from their dormancy period in spring and grow strongly through the summer. The fungi are most active at the same time that the trees are most active. In winter the trees become dormant and so do the fungi. It is in the winter dormancy that the fungi form into the hard, black, knotted tubers beneath the ground.

In conclusion Raylene states, “There is a large degree of secrecy about who is planting truffle beds and where they are planting them.
“Despite this, we know from our involvement with the industry, that there is a reasonable amount of activity out there. The industry is at an early stage in Australia that no one knows for sure whether it will be successful or not. Some farmers are planting groups of just ten trees to see how they turn out, others are planting larger areas and gearing up for higher volume production.”

 

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