Institute Dr.Khanaqa

1. Site Selection

Climatic Requirements

Mean daily temperature:	Summer: 17.0°C to 40.0°C Winter: -5.0°C to 8.0°C
Annual rainfall:	300 mm to 1500 mm
Time of rainfall:	Brief, heavy rainfall in spring will trigger the initial truffle growth. Brief, heavy rainfall in summer or autumn will ensure high yields.
Periods of drought:	In case of long droughts (> 20 days), irrigation is essential.

Soil Conditions

For the commercial cultivation of truffles, the field should be free draining, well aerated, sufficiently calcareous (pH value) and deficient in nitrogen. Loess soil is favoured for growing truffles, because it fulfils the required conditions. However, it is also possible to grow truffles on light, sandy soil or on chalky soil. Chalky soil can only be recommended in very special cases (and only for Périgord truffles).

pH Value

The pH value of the soil is one of the most important conditions for viable cultivation of truffles. Ideally, the natural pH value of the soil should range between 7.0 and 8.5. For a pH value below 4.5, truffle production will be inhibited because of aluminium toxicity. If the deviations are small, it is possible to regulate the pH value (raising the soil pH by liming).

Mineral and Nutrient Content of the Soil

• Macro elements: N, P, K, Mg
• Micro elements: B, Cu, Mn, Zn
• C/N ratio

The most favourable mineral composition for truffle production varies from soil to soil, since it depends on many different factors, such as soil type, soil structure and content of organic matter. Accordingly, it is not possible to specify generally valid conditions. Before establishing a "truffle", or truffle plantation, it is absolutely imperative that the soil in question be analyzed and evaluated for its suitability. Both the topsoil (15 - 30 cm) as well as the subsoil (30 - 60 cm) should be examined because they are very vital for the relationship between fungus and host (topsoil) and general root activity (subsoil). Soils with a high heavy-metal content are unsuitable for growing truffles, because the development of fruit bodies (i.e. truffle formation) will be delayed or even inhibited.

A truffle should not be established on an area which has been used intensively for normal agriculture, since these soils usually exhibit a high level of nutrients and frequently also pesticide residues.

2. Establishing a Truffle

Preparing the Ground

In order to aerate the soil and remove the weeds, the soil should be ploughed first (ploughing depth 30 cm).

Planting

Planting time:	Autumn (October/November) or March. The truffle-infected plants are delivered in pots. The trees should be planted together with the entire substrate in the pot, as it is penetrated by the inoculated root system.
Planting density:	1000 - 1200 plants/hectare
Planting distance:	3 meters distance within and between the rows
Planting system:	Monoculture or mixed cultivation is possible. Alternate planting of the seedlings (hazel, oak, olive, almond) within the rows, as well as hexagonal close packing, is recommended. Mixed planting offers the benefit that the stronger vegetation of hazels will promote the development of fruit bodies, thereby ensuring earlier and better yields. However, the cultivation of hazelnut saplings involves more work, as the foliage has an acidifying effect on the soil and must therefor be transported out of the field in autumn.

3. Maintenance and Cultivation Work

Irrigation

To guarantee proper growth of the truffle-infected trees, thorough moistening of the soil is imperative. In almost all cases, watering is needed during the first few months after planting. Furthermore, supplementary irrigation is advised from the first to the third year.

To ensure high yields, the field must be irrigated whenever necessary during the whole period of cultivation to increase the yield.

Irrigation quantity and frequency vary strongly, depending on the soil type and climatic conditions.

Irrigation systems:

• Overhead irrigation/sprinklers
• Mini-sprinklers
• Droplet irrigation (spiral irrigation pipes)

Quality of the irrigation water: The presence of pesticide residues must be excluded. Undesirably high nutrient or pollutant levels should be removed (with the aid of an osmosis installation, for example).

Soil Cultivation and Care

Rotary tillage: In the fourth and sixth month after planting, at a depth of 3 - 5 cm. In the following years, twice a year in the same manner. The aim in soil preparation is to aerate the soil and to remove the weeds during the cultivation period.

In autumn, the hazel foliage must be taken out of the plantation, because otherwise it would acidify the soil (i.e. reduce the pH value).

Whenever necessary, correction of the soil pH (liming) should be carried out.

Fertilization: Organic manuring, in order to raise the levels of organic matter in the plantation and to stabilize the soil moisture content. A mixture of vegetable and animal products should be added, with pH < 8.0 and carbon/nitrogen ratios about 10 or more.

Plant Protection

Damage caused by wild boars, hares, rabbits, mice or squirrels: The truffle should be fenced in. Fencing could also be necessary to prevent theft of the truffle-infected plants and the truffles themselves.

Parasites: Leaf-rolling caterpillars, aphids, truffle fly (Suilla gigantae, formerly Heliomyza tuberivora) in France and Italy.

Fungal diseases of the host plants: Powdery mildew, for example.

Lifetime of a Truffle

With long term production, the brules (truffle-producing zones, whereby the truffles tend to grow at the edges) grow and coalesce. It is then necessary to remove individual trees to increase the space between the remaining trees.

Almonds 20 - 25 years, hazels and olives about 25 - 30 years, oaks on average 30 years. Given suitable pruning and thinning out of the trees with increasing age, the truffles may produce for up to 50 years (oaks).

4. Harvest

Harvest Methods

• Dogs (specially trained)
• Pigs (used traditionally because of their natural sense of smell, but no longer)
• Mature truffles are indicated by cracks in the soil (but only light soil)
• Another pointer to ripe truffles is the appearance and "dance" of the truffle fly (France, Italy)
• Careful digging with a spade. Avoid injuring the root system!
• Electronic detectors, detection of the volatile substances emitted by the mature truffles (flavour, perfume)

Harvest Time

Summer truffle (T.aestivum Vitt.)	Summer (June - July)
Khanaqa truffle (hybrid: T.melanosporum Vitt. x T.magnatum Pico)	Middle of March - middle of May
Perigord truffle (T.melanosporum Vitt.)	Winter (November - March)
Arabian truffle (Terfieza)	Spring

Start of Production and Yields

About 3 years after planting:

Summer truffle (Italy, France)	150 - 450 g/oak
Khanaqa truffle	150 - 450 g/oak

About 3.5 years after planting:

Perigord truffle (France)	150 - 450 g/oak
Arabian truffle	450 - 650 g/oak

If the conditions for growing truffles (soil, climate) are favourable, the plantation's yield increases year by year.

Prices (2001)

Summer Truffle	200 - 300 US$/kg
Arabian Truffle	130 - 150 US$/kg
Khanaqa Truffle	800 - 1,000 US$/kg
Perigord Truffle	1,500 - 2,000 US$/kg

Crop Yields (2001)

Italy and France in total	about 130,000 - 140,000 kg/year
Summer truffle (Italy, France)	about 110,000 kg/year
Périgord truffle (France)	about 25,000 kg/year

Characteristics of the Truffle Types

Summer Truffle:	Flavour weaker than the White and Perigord truffles, but earlier and higher yields, sold fresh and tinned
Khanaqa Truffle:	Hybridization of Perigord and White truffle, quality similar to these types, flavour weaker than the parental generation, but earlier and higher yields
Perigord Truffle:	Strong flavour, sold fresh, high price
Arabian Truffle:	Weaker flavour than the Perigord truffle