Briefly truffles like: There are many suitable climatic zones in Australia which are generally Temperate. Our soils need to be ameliorated with lime and/or dolomite to adjust the pH to the desired level. A soil test is required to determine how much lime is required to raise the pH (see Truffle Soil Test page). NB/ Agricultural soils that have been heavily fertilised (NPK) or had chicken manure used may be too rich in available phosphate and may not be suitable to growing truffles.
Soil Amelioration Nutrition of trees The general advice is not to use mineral NPK fertilisers but to encourage the organic system. A healthy organic soil is rich in Actinomycetes (a false fungi responsible for decomposing organic material) and many types of soil bacteria especially photosynthetic bacteria and nitrogen fixers. These become the food sources for the next level of protozoans which keep spring tails and other macro fauna happy. You can usually identify when your soil is bio-active by the strong presence of tiny animal life, including earthworms, and a rich “earthy mushroom” smell (this is the actinobacteria at work). The result is freely available organic nitrogen and a range of naturally chelated plant nutrients. In short a healthy, well balanced soil. Generally the required level of organic activity in Australian soils is low so plan to stimulate soil microbes with organic supplements (see information on kelp, fish emulsion, worm leachate, biochar and molasses). The Truffle Ready Soil test is able to make recommendations for the addition of organic supplements. The applied calcium (lime) can be leached over time however building a strong organically rich soil will tie up the calcium and reduce the losses. ESTABLISHING THE TRUFFIÈRE
As soon as practical install a two metre high ringlock wire fence around the entire truffière to prevent damage from kangaroos and wombats, etc. PLANTING METHOD
SPECIES & SPACING A commonly used practice is to use a planting pattern of one Q. robur, two hazels, one Q. ilex. This is repeated down the row and the next row is off-set (i.e. one Q. ilex, two hazels, one Q. robur). The most commonly used spacing is 3 metres between plants and 8 meters between rows. This works out to be about 400 trees per Hectare. The theory of this set up is that the hazels will come into truffle production earlier than the oaks and eventually the larger oaks will fill the canopy over the Hazels. The hazels can later be removed as they fall out of production and this will reopen the canopy to allow entry of light. Of recent many growers are tending towards wider spacing between the trees (4 metres) to maximize winter light on the soil. Some growers prefer to only use Oaks and not Hazels because hazels do require a little more pruning maintenance in winter. At our truffière in Gembrook we have included Quercus suber and are trialling a number of different planting patterns and different spacing. Also we have inoculated an extensive range of Quercus species and the ones that show good infection will be used in future trial plantings. Under trial are Q. pallustris, Q. cerris, Q. lobata, Q.faginea, and Q.coccifera. MAINTENANCE OF THE TRUFFIÈRE IRRIGATION Generally while the trees are young sprinklers with a small diameter are preferred to avoid waste and excessive weed growth. As the trees grow the sprinkler size and throw capacity needs to be increased to water out to the “drip zone” of the tree. Sprinklers are available to accommodate this requirement. At Gembrook all poly-pipe main lines (40mm) and laterals (25mm) are buried underground to avoid heating up the water. All rows are solenoid controlled from a time clock. All rows have flushing valves on the ends of the poly line to flush the system every few months and prevent sprinklers blocking. The sprinklers are a Toro Waterbird VI PC and are connected to the 25mm poly line by a 5mm micro tube with a stake. These sprinklers deliver 36 litres per hour (at 1.5 bar pressure) and the diameter of the watering pattern is 5.4 metres. When the plants are small the sprinklers (on stakes) are kept inside the tree guard to avoid wetting unneeded areas. Be aware that in summer exposed poly pipe can build water temperatures to a point that can be damaging to roots and of also any foliage that comes into contact, especially when the plants are still young. Some method of soil moisture monitoring needs to be employed to either trigger the automatic system or advise the irrigator of the right time to commence irrigation. Experienced irrigators can tell the moisture content of their soil by feeling it however more accurate measurements can be obtained using a range of soil moisture sensors. Significant water savings of up to 50% can result. Some of the soil moisture sensors available include: Some systems can be connected to computers which automatically switch on watering systems when soil moisture levels fall below an established level. We can offer customers help in designing a suitable irrigation system, if required. WEED CONTROL Any unchecked excessive weed growth around the truffle trees will rob the plants of moisture, nutrients and light and will affect tree growth. In the past Round-Up (Glyphosate) was seen as the best remedy for weeds. Round-Up is translocated within the plant and kills the roots of weeds and was thought to be de-activated in soil so not affecting roots. However, recently growers have been alleging that Round-Up may indeed have an effect on root growth and truffle mycorrhiza. Some growers are using Basta (glufosinate-ammonium) and are suggesting it may be a better alternative. It is a fast acting knockdown controlling a broad range of grasses and broadleaf weeds without any soil activity. The safest way to control weeds is either mechanical (pulling or slashing) or cultivation. If mowing is used to control weeds then a side throw mower should be used to direct the grass clippings away from the trees. Grass clippings and mulch will increase acidity in the decomposition process. Shallow cultivation (with spring tynes) can be used in early spring to increase soil air porosity (aeration) and check weed growth. A brûlé is a marked area of ground around a truffle infected tree that appears burnt. It is thought that the mycorrhiza produces phytotoxic chemicals that burn the weed’s roots. The brûlé is an indication that the truffle fungus is active and quite often signals the beginning of truffle production in the next few years. PRUNING Pruning is required in the formative years to develop a central leader and remove all side branches near the ground. Oaks are apically dominant and generally require very little pruning. The aim when growing the French black truffle is to produce a tree with a single trunk to about 1 metre high and then the foliage in an ice-cream cone shape. This allows easy access under the tree canopy for weed control, entry of light to the root zone, an even irrigation watering pattern and eventually access for harvesting of truffles. Hazels produce many suckering basal shoots that need to be removed with either pruning or spraying with Basta in winter or early spring before bud burst. PEST AND DISEASE CONTROL There are several diseases that can infect truffle infected trees including powdery mildew, stem cankers, wood rots, spots and rusts. However care must be taken before using chemical control methods because of the possible affects on the mycorrhiza. Many diseases can be less troublesome if preventative measures are used. Firstly watering only in the early morning so that foliage is dry at night and also not irrigating in the heat of the day can limit the spread of unwanted fungi. Powdery mildew is one disease easily spread in a high humidity greenhouse and in the field when climatic conditions are favourable. Good preventative and hygiene measures can be successful in limiting the spread of this disease. Care must be taken with the use of chemicals however small outbreaks can be controlled with a spray of Milk (1:5 rate). Don’t allow any run-off onto the soil. The milk kills the powdery and is then broken down in sunlight. Occasionally insect pests like aphid appear on new soft growth. These can be controlled using a garlic or pyrethrum spray. Various caterpillars can be controlled using pyrethrum or a biological agent “Dipel” which is a bacterium that kills grubs and caterpillars. HARVESTING METHOD Timing of harvest Dogs to locate the truffles A trained truffle dog with his strong sense of smell can detect the presence of a truffle growing beneath the soil. They are trained to indicate the spot where a truffle is growing. We know of one dog handler who has dogs that can distinguish between an immature truffle and a perfectly ripe one and indicates by “pawing at the ground”. There are companies that are currently developing electronic truffle detection devices, known as an e-nose (under development so watch this space!)
Harvesting method After harvesting the truffle remove the excess soil by gently brushing. Washing the truffle in water may hasten the deterioration process. Then maintain refrigeration (which is easier in winter) and send to the wholesaler or customer as soon as possible. Methods for transporting truffles to market especially for export are currently being studied. Several methods of packaging and oxygen replacement with nitrogen gas are all being trialled to determine the best method to maintain quality. |
