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Truffles
Fungi
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Soils Which Produce the Truffle
by Fabio Primavera

Truffles do not grow anywhere, even if the area as the whole can be defined as productive and some of the conditions necessary to its development are present, such as the plant being well mycorrhized and the ground having a high pH. Using information deduced from the study of the environmental soil of natural truffle bed, an expert pedologist (pedology = the science of the soil) is able to supply advice on the choice of site location and on the management of truffle cultivation.

After years of attempts, some successful others much less so especially those concerning the Italian Valued White Truffle (Tuber magnatum Pico), truffle cultivation is increasingly becoming a modern and rational arboreal culture, run by all the agricultural means available, such as the tillage and corrections of the soil, irrigation, temperature control of the air and soil etc., with ever increasing chances of success. All this is consequence of the discoveries made from 1990 to today by a group of Italian researchers, to which body the editor of this piece belongs, on the relationship between the chemical-physical characteristics of the environmental soil of a truffle bed and its entry into productivity. The first positive results, such as the recovery of non-productive implantations, the revival of productivity in degraded natural truffle sites or the first fructifying of new implantations obtained by applying agronomical techniques deduced from our own research, drive us to divulge the results of our experiments as far as possible in order to prevent truffle cultivators from repeating costly failures.

 

The Fundamental Characteristics Of Truffle Soils

In Italy there are seven truffles of commercial interest (see Act. n.752 16 December 1985 and successive regional legislation), amongst these two are more esteemed and less widespread (Tuber magnatum Pico, the White Italian Truffle, and Tuber melanosporum Vitt., the esteemed black), as opposed to the others which have much vaster home grounds of development and are therefore found more easily. It has been noted, for example, that in the home ground of the "Bianchetto" (Tuber albidum Pico) there are islands of the esteemed white and in the home grounds of the "Scorzone" (Tuber aestivum Vitt.) there are islands of the esteemed black, whose presence has also been noted very close to Tuber magnatum Pico, Tuber albidum Pico and Tuber aestivum Vitt., which is certainly not coincidental. It has been proven that this fact arises from the nature and characteristics of the site’s soil. To start off with, let’s analyse the demands of the rarest and most acclaimed truffle in the world and we will see the essential factors for the growth of the Tuber magnatum Pico and what differentiates its environments from those of the other truffles. To summarize the fundamental points we can state that:

  • the soil must be soft, that is it must be full of big pores;
  • it must be moist for a large part of the year;
  • it must be rich in calcium.

The Tuber magnatum’s fruiting body needs a larger quantity of oxygen than its rivals, which comes from a better air circulation in the soil, which is why a large number of pores are necessary. A higher oxygenation is also derived from the reaction of the ground, which must be weakly to moderately alkaline, as a result of the presence of calcium in ionic form. This condition instantly blocks the carbon dioxide to the full advantage of the oxygen concentration in the solution circulating in the soil. From a climatic point of view the critical period is Summer, given that the ground temperatures must not be excessive and that the soil has to be moist but not saturated, in order to protect the mycelium and the young fructifying bodies from drying up.

Where Tuber magnatum Pico Is Found

Presupposing that the materials which make up the soil must be rich in calcium and that the microclimate must be cool and moist even in Summer, the esteemed white truffle grows where dynamic external agents recreate, year after year, a soft and porous stratum which can be easily colonized by the fungus and within which there is an abundant circulation of air. The combination of these factors in nature is not very common, besides which the duration of these conditions must be synchronized to the fungus’s annual cycle. The environment of the "Crete Senesi", for example, has a soft and porous stratum which is created annually by the autumnal rains. These provoke rapid and localized floodings of water courses in the valley-bed; the earthy materials carried by the water are therefore rapidly and chaotically deposited along the banks creating porous soil structures. In the successive Spring, this stratum, completely devoid of vegetation and full with large pores linked to the exterior, is rapidly colonized by new mycorrhized roots and, later on, by the mycelium.

If the Summer climatic conditions are favorable, so as to keep alive the mycelium of the fungus and the largest possible number of young fruits, there will be a good production of Italian white truffle in Autumn. This cycle has to be renewed every year because the soil tends to recompact itself and lose its porous nature as the holes are filled up with the fine materials carried by the water to its interior, the effect of the beating rain, and the clogging effect of roots from herbaceous species which successively colonize the ground.

To generalize, the valued white truffle’s environments are deriven from a strong and dynamic morphology in a calcium-rich environment, with a rainy climate whose Summers are cold and damp. It is therefore possible to find natural truffle sites along slopes with small, superficial landslide movements (as in the dynamics of the mountain sides in the San Miniato area, or all along the Apennines from the Emilia region to highest areas of our South. At times there is a combination of alternative freezing and thawing which, every year, recreates a porous stratum which is sufficient for the development of the white truffle. (as in the climatic dynamics of the Mugello or Montefeltro areas). At other times this phenomenon is the consequence of man’s unknowing actions in his working of the land which is not excessively deep, especially when the soils are formed by stable materials which do not lose their porous structure, resisting more than others to the compacting effect of the rain, as in the case of calcareous marls of the Acqualagna and Piemonte areas. From all this it can be understood how different, at first sight, the white truffle’s environments can seem, but in reality they are specific and similar if looked at from the triffle’s point of view. Being a hypogeous fungus with very unflexible biological demands, it is the pedo-environment which must be valued on the whole. This is why areas which seem different but which have in common the three fundamental soil conditions, with the presence of well mycorrhized plants, are chosen by the truffle for its reproduction. 

Source:

  • TartufiMania (no longer on the web)
The fungi that produce truffles are obligate symbionts (required partnership) of certain trees. The species are native to Europe. In Italy and France landowners buy inoculated seedlings, oak and Corylus (hazelnut) from nurseries. Habitat ideale del tartufo è senza dubbio il territorio ancora ricco di boschi. Tra le piante tartuficole più diffuse del luogo si contano latifoglie come pioppo, salice, tiglio, nocciolo e carpino, alla cui ombra matura, da settembre a dicembre, il prezioso tartufo bianco (Tuber magnatum Pico), particolarmente profumato e ricercato dai buongustai.

Sources:

  • Text: The History of the Truffle - http://www.ottavia.com/truffles_history.html
  • Text: ItalMangia.com - Truffles... the white diamonds of cuisine - http://www.italmangia.com/about_white_truffles.html
  • Citta' Castelli Ciliegi - La Strada dei Vini e dei Sapori - http://www.cittacastelliciliegi.it/b_tartufo.htm
  • Photographs - http://www.agraria.org/funghi/tubermagnatum.htm

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Created: Wednesday, January 09, 2002; Last Updated: Wednesday, September 14, 2016
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