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The soil

Our great ally

The black winter truffle is a fungus that is found in soft, calcareous and well-drained ground where fertility is low to medium. In order to find out what conditions the plot you’re thinking of planting has, it is necessary to perform a soil analysis to learn whether it fulfils the needs of truffle trees.

Here are the analysis parameters and the approximate ranges most suitable for truffle cultivation.

We recommend having the analysis done at a certified laboratory with a proven track record, because otherwise, the results will reveal little—or nothing—about what you’re trying to find out. The results of the analysis should be assessed by someone who—aside from being knowledgeable about soils—is familiar with trufficulture.

A soil analysis should not be read parameter by parameter. Instead, it should be interpreted as a whole. It is also worth pointing out that there are plots that have good yields whose values are well below—or above—the figures mentioned below, for which we show their respective soil analyses.


*Soil analysis for truffle plantations with yields > 40 kg/ha/year


Analysis parameters

The soil sample to be analysed that is to be collected must be representative of the plot in question and taken following the instructions given by the laboratory that will perform the analysis.

pH in water (H2O) – The right pH should be between 7.5 and 8.5. It wouldn’t hurt to also analyse the pH in potassium chloride (KCl), as it is much more stable than in water.

Conductivity – It cannot be saline soil. It has to be between the normal values for most crops.

Total Carbonates – The range is very broad. There are many plantations with good yields that have very low quantities of carbonates, and others that have up to 70% or more.

Active Limestone – The same criterion for total carbonates. It is commonly found between 0% and 30%.

Calcium exchange – Quite variable, although most plots with good yields generally have 5000 ppm. Range between 1,000 ppm and 12,000 ppm.

Organic matter – Content is usually between 1% and 10%. It Spain, it normally ranges between 1% and 3%.

Kjeldahl Nitrogen – Normally found between el 0.1% and 0.3%.

C:N Ratio – Range between 4–20, with 10 as ideal.

Olsen Assimilable Phosphorus – Ideally found below 20 ppm. There are plantations with good yields that have content of up to 40 ppm. It’s not that higher quantities are not viable, but you have to be very careful with significant quantities of this element in the soil.

Potassium – Generally found between 0.01% and 0.03%.

Magnesium – The content is quite variable. Anything less than 0.01% can be considered poor.

Texture – Balanced textures such as loam. It is important to point out that it is not a matter of texture but instead of structure, which should be granular or lumpy. We say this because laboratories normally do not analyse soil stoniness. This factor can be important when dealing with textures with high clay, silt or very fine sand content.

Texture should be analysed according to five fractions (coarse sand, fine sand, coarse silt, fine silt and clay). For soils that are somewhat heavier textured, soil slope may be favourable.


Is it advisable to take the climate factor into account?

It is advisable to consider the climate. Extreme climates—whether too cold or too hot—are not recommended; neither is scarce or irregularly distributed rainfall.


How should I prepare the ground?

Once you’ve determined whether the plot has the right conditions to grow truffles, you should carry out the relevant preparatory work to plant the tree seedlings under the best conditions.

The work to be done will depend on the previous crop cultivated in the field in question.