The host environment and trees of the two most prized species

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The Tuber magnatum is to be found at the bottom of valleys and on hillside areas which are not too dry.

These soils, characterized by the features of the rocks from which they have been formed are of clayey-calcareous type, which are usually compact, often the top layer being more compact with the lower layer being lighter. In this last case the soil is often mixed with coarse sand or stones, but the lower layer is compact therefore permitting the growth of the superficial roots. These soils are generally derived from marls and calcareous sandstone, and are therefore rich in calcium carbonate. The soil may be covered by fields or with scarce vegetation, but free of scrubland and fairly humid. A clayey-calcareous soil that is not too dry, also being the ideal conditions for the growth of the symbiont trees themselves which are principally the following: the Farnia-oak (Quercus robur), the Turkey oak (Q.cerris), the bay oak (Q.petraea), the chestnut young oak (Q.pubescens), the black poplar (Populus nigra), the white poplar (P.alba), the Caroline P.deltoids cv.carolinensis, the Aspen (P. tremula), the large willow (Salix caprea), the wicker (S.viminalis), the white willow (S.alba), the linden (Tila platyphyilos), the black hornbeam (Ostrya carpinIfolia) and the hazelnut (Corylus avellana).

Exposure is not so important, although excellent findings have been recorded in areas with a north or north-westerly exposure.

The tree coverage must be around 50%, there must be little or no scrub vegetation and herbaceous plant coverage must be between 20-70%.

Inland areas are more favourable as the ground hydrographical conditions remain more constant thanks to the greater rainfall on higher land than the coastline.

Prolonged summer droughts are detrimental to the growth of the T.magnatum and its symbionts; which belong to a category of continental flora characterized by a more differentiated seasonal temperature range.

While, like all fungi, summer rains tends to promote their growth.

The best areas being valleys sheltered from the wind, thereby avoiding the rapid drying out of the land and temperature lowering.

The white truffle is to be found at altitudes not exceeding 700 a.s.l.

The soil acidity is of fundamental importance; which must come within a minimum pH of 6.8 and a maximum of 8.5.

There should preferably be scarce organic substances in the soil. Therefore a precise combination of factors are necessary; in terms of environmental conditions, chemical composition, soil humidity and climatic conditions.

Therefore we can conclude by saying that the soil should preferably be of marne-calcareous type, at a height of under 700 m, it should be fairly ventilated but not too permeable, with a fair humidity content of the surface layer even during the driest months, it must have a fair calcareous content and should be poor in phosphorous and nitrogen, and rich in potassium with a pH of between 6.8-8.5, with a scarce organic substance content, moistened by summer and spring rainfall, possibly in the vicinity of water courses at the valley bottom, but without any backwaters, and with a modest slope (approx. 15%).

The ideal soil conditions for the Tuber melanosporum must feature a calcareous and/or clayey-calcareous sub-soil made up of fairly fine granular particles and calcareous stones bound together by marne material, sand, and other filling material.

These soil conditions are often present in hilly environments with trees planted at a distance of between six and twelve metres apart (according to the age and development of the tree), forming sparse woodland, with areas of sparse spontaneous vegetation.(plateau).

It is possible to see the signs of the presence of the truffle in these areas; such as irregular cracks and fissures in the soil, the presence of the specific truffle insects and traces of previous hollows.

The T.melanosporum requires calcareous-stony soils (permeable) with a compact sub-soil, which promotes surface root growth.
The clay content must not exceed 40%, otherwise it is not sufficiently water permeable, which may lead to a conditions of asphyxia.

These soils are very rich in calcium carbonate and poor in organic remains.

In excellent black truffle growth soils there is almost a total absence of humus.

It also grows in soils with a richer content of organic materials, the phosphorous and nitrogen content however always being limited.

Thanks to the marked calciphilia and basophilia of the T.melanosporum, it lives in symbiosis mainly with the following trees types : the Young oak (Quercus pubescens), the Acorn (Q.ilex), the Turkey oak (Q.cerris), the linden (Tila platyphylios), the hazelnut (Corylus avellans), the Black hornbeam (Ostrya carpinifolia), and the Cistus (Cistus spp).

The most productive truffle growing areas (in terms of number and actual truffle size) have a south or south-easterly exposure.

The tree coverage must be of around 30%, the shrub coverage should be scarce or non-existent, while herbaceous plant coverage almost nil (plateaus).

A good light penetration is necessary to heat up the soil.

Despite being xerophilous, extended drought conditions are detrimental, especially in the summer months.

Both higher inland areas and costal areas may be suitable.

A much more rustic example of the prized white truffle, can even be found up to a height of 1,100 m. a.s.l.

The soil pH value is again the most important parameter and must come within a range of 7-8.5.

To conclude, the terrain must be superficial, permeable, ventilated and quite stony and rich in lime, with pH ranging from 7 to 8.5, and at an altitude of under 1.100 m, with a rich clay content, with scarce organic substance, without any backwaters, exposed to the light and not exposed to the North (except in exceptionally hot and dry areas), poor in phosphorous and nitrogen and rich in potassium.

Good iron content may also be useful.

Recent studies undertaken by the Experimental Soil Study and Protection institute of Florence, have revealed that the best soil conditions for the growth of the truffle (whether white or black), are those with a highly disordered composition, as the disorganization of the component material favours the interconnection of the vacuums. Therefore the macro and micro soil porosity is of fundamental importance.