1- What are truffles and what varieties are there?
2- Geological characteristics of truffles
3- Characteristics of a black truffle producing soil
4- Climatic characteristics for black truffle
5- Previous crops before planting truffle
6- Choice of host truffle plant. Planting density and layouts
7- Preparing the land for truffles
8- Economic considerations – Cash flow for a truffle farm
9- Profitability of truffle farming
What are truffles and what varieties are there?
Profitability of truffle farmingTruffles are the fruit of a mycorrhizal fungi. That means that lives associated to the roots of some host trees or shrubs, as oaks, holm oaks and hazels, Cistus or some pines. Truffles fruits into the ground and some species become aromatic with the aim that some animals dig them up the ground and while eating them spread their spores. The aroma is also appreciated by humans and recognized by dogs that can be trained to harvest them.
Truffles belong to the genus Tuber. There are several species, around 40, but just a few of them have a real market value, like the black truffle or Perigord truffle Tuber melanosporum, the winter truffle Tuber brumale, the summer truffle Tuber aestivum and its autumn cousin, the bourgundy truffle Tuber aestivum var. uncinatum; the white truffle from Piamonte Tuber magnatum, with great value, but its cultivation still has random results and its lower priced bianchetto Tuber borchii.
Most information in this booklet is related to melanosporum, if you want extra information about other truffles, you can check these links
Burgundi truffle (Tuber uncinatum) https://micofora.com/en/growing-tuber-aestivum/
Bianchetto (Tuber borchii) https://micofora.com/en/growing-tuber-borchii/
White truffle (Tuber magnatum) https://micofora.com/en/growing-white-truffle-tuber-magnatum/
Ecology of truffieres: Geographic, geologic and topographic characteristics
Black truffles appear naturally at altitudes between 100 and 1500 m.a.s.l., the higher the altitude, the sunnier the exposure. Same effect occurs with latitude, as we move north to colder climate, truffle needs extra sunlight, south facing slopes or lower canopy inside the orchard.
It is advisable to choose areas with a slight slope to avoid waterlogging of flat lands and valley bottoms (unless they have a subsoil with good drainage), avoid erosion of very inclined lands, where the installation and mechanization will also be more complex.
The black truffle grows naturally on limestone soil in the Mediterranean region. In Spain, these are the majority in the eastern half of the Peninsula and are found on rocks of geological age framed in the Primary, Secondary-Mesozoic (Triassic, Jurassic, Cretaceous), Tertiary and alluvial periods of the Quaternary or recent, with a predominance of hard limestones of the Upper Jurassic.
Black truffle soil characteristics
Although texture, carbonates, and most nutrients have great variability, we recommend to make a soil analysis. Soils can be easily modified before planting, but some of red flags we try to avoid are: clay over 35% to avoid compaction; and we want these nutrients to be below: Phosphorous <40ppm, Nitrogen <0,5%, Potassium <600ppm. Truffles need active carbonate and we like the Calcium content to be around 10.000ppm. We think calcium ion is the ammunition truffle mycelium uses to stress the tree while asking for sugars.
Once the orchard is mature, we prefer to make leave analysis as we have now patrons for these nutrient concentrations in order to have a healthy tree with higher photosynthetic activity, so it can create more sugars to feed more truffles in the ground.
It is important as well to check the soil structure trough the study of the horizons digging some profiles before soil preparation and planting.
So, to know if we can grow truffles on a soil we should study the horizons, confirm the presence of carbonates and analyze the pH (that should be between 7.5-8.5). If we have to raise pH, as a rule of a thumb, we add 2 tons/hectare to raise every 0,1 of pH. This is 40 tons/ha of crushed lime stone to raise from initial pH 5,8 up to 7,8. Lime need to be incorporated mechanically mixed into the soil top first 20cm.
Soil should allow water and air to drain trough.
To check if the soil has any carbonate we can just drop diluted hydrochloric acid and see that the soil boils (effervescence).
Soil profile
Should not have discontinuities between layers, with some difficult to mark limits between them.
Crumble structure and spherical particles. Avoid prismatic structures, sign of lixiviation. Laminar structures shows compactation and flood. Bad soil structures get grooved and heavy on dry weather.
Climate
Black truffle is adapted to dry and hot conditions, humid temperate or cold sub humid Mediterranean climate. Hot and humid springs, dry summers with some storms, no frost at the beginning of autumn, and winters with no long periods below freezing. Note harvest is done during winter, so areas with average temperatures below 0ºC or with long periods of snow cover with have troubles, first freezing truffle fruit bodies below ground and second running dogs for the harvest.
Rain between 425-900 mm. (600-1500 mm in Italy and France). 48-64 mm of rain monthly from June to the end of august, from a few summer storms.
Note Tuber melanosporum is formed late May and early June, although it can be several “births” during all summer, so there is a moisture demand in the ground in summer and autumn to increase weight. More information about the birth and development of truffle fruitbodies in this link:
So, we strongly do not recommend to plan any truffle (melanosporum) farming project with no irrigation. The use of peat-moss based products to make the Spanish wells or truffle nests to add the male factor in this industry, has led to increase the demand of water, increasing mostly frequency of irrigation to avoid truffles to dry up during summer.
Previous crops
Previous crops will condition the organic matter contents and fungi contaminations on the area we’re planning to plant the mycorhized seedlings.
Best previous crops are cereals, pulses, lucerne, most of fruit trees as they do not host contaminant fungi (except hazels, figs, pecans, walnuts).
We recommend to open a trench to cut roots of these trees and avoid contaminant getting into the future truffle orchard. This trench can be used as a drain trench as well. We can leave it open (risky for the tractor) or cover the wall with a fabric geotextile and fill it with rocks.
Note most roots of wild trees can run a distance of 2 times its height.
Host plant election
Truffles grow in symbiosis with a wide variety of plants (see next chart). But just some of them are used for its cultivation. Actually, in Spain about 90% of black truffle plantation are done with the cold hardy holm oak (Quercus ilex ssp. rotundifolia), and secondary oaks (Quercus pubescens, Quercus faginea). Hazels (Corylus avellana) have been almost abandoned for black truffle growing due to their higher rates of contamination in a long term and to realize that co-crop of hazels and truffles is complicated (for instance, hazels need to be harvested in the fall when soil is moist using heavy machinery that will compact truffle fruit bodies in the ground). In some countries they are sensitive to the filbert blight, although some resistant varieties are being released to the market. On the other hand, in the west coast of the US, evergreen oaks can be more sensitive to the sudden death oak, although the European strain of this disease is not affecting well managed and irrigated (low stress) plantations.
Density and platation distances
We recommend densities between 300-600 trees/Ha for the black truffle. In the past we were choosing less density as soils were deeper and rich, as trees would grow faster. But there is in all farming a tendency to mid -high tree densities, in order to get higher yield balancing management costs though specific machinery. The higher the density the higher the early yields, although note in the long term (over 20 years old plantations) yields could be the same no matter tree density, as yield is more related to final canopy.
In warmer and high radiation climates black truffle will look for shade and closed canopies (80% canopy), while in cold climates with low radiation at higher latitudes, black truffles look for direct sunlight with canopies around 40%. As a rule of a thumb, when average temperature in the hottest month is over 23ºC or when radiation the same month is over 8kWh per square meter, truffle starts to look for extra shade and we have to give it somehow.
In the old times plants were located at 6×6 or 7×7 but nowadays most layouts are 6x3m. In this case rows are better planted north to south, allowing sun to light the center of the whole row. Otherwise, if you make rows East-West, you create a side of the tree with extra sunlight where the loss of water is higher and fruitbodies normally smaller than in the north side of tree hedges.
Modern truffle farming is all about avoiding soil compaction and to step over the active truffiere and this is achieved using off-set implements. The use of this machinery has made that we always need a minimum row width of 6m.
In the picture below right, an off-set implement used to add new spores in trenches every spring in a high-density orchard. Here a video of these implements working:
Outplanting
In the right figure you can see the most common tasks and machinery used to prepare the soil for planting a truffiere.
If you have to lime, as normally this is done using heavy machinery, rip or subsoil after that. Mind that no soil compaction is one of the main pillars in truffle farming.
Planting can be done manually, although large plantation better and cheaper done with GPS tractor as in the link:
Right after planting, sometimes we use a fabric geotextile, white on top, black underneath to avoid weed control the first 3 years. Trees will be for a few minutes under the fabric and with a cutter we pull them out:
https://www.youtube.com/watch?v=admOxYk5zqw
But fabric mulch can be easily substituted using an in-row blade for weed control like this one the first 3-4 years:
Economical features about truffle
The black truffle and summer truffle growing areas have limestone soils, generally of a poor quality. These areas in south of the Mediterranean in Europe are used for crops associated with low agricultural performance. These farms depend on financial aid for their survival. Truffle growers do not have to depend on subsidies any more, as they can triple the income earned from traditional crops in these areas, and the value of farming land may even increase in truffle growing regions.
On the other hand, in countries overseas (Chile, US, Australia…) the farm land used to grow truffles is a good land where other quality crops can be grown and so it is not so clear than the incomes from this crop are much higher than others (cherries, berries, table grapes, etc). It is important to do a good due diligence before getting into this crop adapted to each country.
Spain, where it is estimated that some 10,000 families are involved in truffle growing and truffle gathering, accounts for 30-50% of world black truffle production. Very few people now work exclusively as truffle hunters. Most combine truffle hunting with other work and/or do it at the weekend, or try to match their holidays with the gathering season. A truffle hunter working a full day currently collects between 3-5 kg of wild black truffle a week, very far from the 8-12 kg a day remembered by old truffle hunters.
The price of black truffles in Spain varies greatly depending on whether the season is good (with plenty of truffles) or not. Truffle prices conform to traditional models, where higher production means lower prices. Truffle gatherers are paid between €200 and €850 per kg for the black truffle. The price paid to gatherers for the summer truffle in Spain is between €35 and €80 per kg.
You can check truffle prices market in these links:
https://trufflefarming.wordpress.com/2024/06/12/how-black-truffle-2023-2024-season-was-in-spain/
Profitability of truffle farming
CASH FLOW IN TRUFFLE GROWING
How much produces a truffle farm? There are references to a single burn being able to produce 10 kg of truffles and to a plantation of oaks mycorrhized with black truffle producing 200 kg/ha/yr. In contrast, some plantations have never started to produce, for a variety of reasons, so truffle farming as a business is not without risk.
But in the modern truffle farming, once standards have been established for tree certification and tree quality has been improved, technical orchards with irrigation, fertilization and adding new spores have pushed orchards to fruit earlier (first truffles harvested years 3-4), most of them stay in 20-40kg/ha/year until maturity, about year 10-14 when most “explode” and reach commercial yields, that could be 40-80-120 kg/ha/year or exceptionally higher.
In Spain, a minimum production of 8-10 kg/ha/yr. is required to recoup the investment made in a plantation. In other countries, with high initial costs, such as liming to bring up the pH, and truffle tree cost higher, more truffles have to be produced before any profit is made, or, to say it another way, the cost of production per kilogram of truffle is greater. 11
Some French truffle growers have remarked that production begins to decrease after 50 years. However, we have found several truffle fields over a hundred years old with burns over 12 m in diameter and in full production. We consider the life span of a black truffle orchard in 30 years and after 25 years most of them get lower yields, with smaller fruitbodies. This is mostly due to increase contamination rates from other wild fungi that colonize the host tree roots year after year, plus looks like truffle enjoy having a new soil “to digest” and once the whole area has turned into a truffiere, something “lacks” in the soil. This is why we do not consider after 30 years to remove the orchard and re plant a new one in the same spot to continue with the same crop, but better move to another crop in the same plot.
Although with irrigation, fertilization and adding new spores we have pushed orchards to fruit earlier (first truffles harvested years 3-4), most of them stay in less 30kgs until maturity, this is after year 10-14 when most “explode” and reach commercial yields, that could be 40-80-120 or exceptionally higher.
Current net values in plantations in Spain, France and Italy range from €19,424/ha to €66,972/ha. The average internal rate of return is always above 9% and the payback period of the investment is equal to or greater than 10 years.
The following table have costs and prices for black truffle farming in Spain. Mind cost per trees and other tasks are lower than other countries.
This is a conservative scenario where yields stay at 40kgs/ha | |||||||
truffle price at whole sale has been considered 400€ (dirty truffles, all qualities mixed)
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