Our concept

Our innovation for the watering of truffle fields


As with any crop, water is an essential part of the truffle production process. The periods of drought are particularly harmful to it. Controlling the watering of the truffle fields is therefore essential to ensure good productivity. In this context, WETRUF, as an innovative start-up, develops and markets tools for truffle growers, allowing the monitoring of the water potential of the soil, and thus a better management of watering.

The interest of knowing the water potential and the water availability of a soil

In a soil, different states of water are identified:

  • Gravity water, which passes through the pores of the soil – the voids – without stopping,
  • usable water, stored in the soil pores and which can be used by living beings (plants, fungi, insects…); it represents the water available in the soil
  • unusable water, present in the soil pores but considered unavailable because it requires too much force to be extracted by living beings.


This proportion of usable and unusable water in the soil varies according to various factors, including soil texture and structure. Therefore, measuring the percentage of soil moisture with capacitive probes is not an indication of the available water in the soil.

Example:
– at 10% moisture in sandy soil -> usable water
– whereas at 10% humidity in a clay soil -> water unusable

The pF, matrix potential or capillary potential, is defined as the resultant energy of water pressure, due to binding effects around solid particles, and capillary effects in the pores. In short, this potential represents the force required to extract water from the soil. This force can be expressed in units of pressure such as Pa or Bar, the pF is then an index corresponding to the logarithmic conversion of the pressure expressed in Pa or Bar.

Theoretically, the pF varies between 1 and 6, but in general, in the soil :

  • at field capacity – waterlogged soil – maximum soil water retention – pF is on average between 2 and 2.5;
  • and the wilting point – the limit at which living things can no longer extract water from the soil – is at pF 4.2. Indeed, the water remaining in the soil pores becomes too difficult to extract by the plants and fungi, the force necessary to its extraction being too important, and thus they “wilt”.

The useful water reserve (UR) of a soil is therefore between pF 2.5 and pF 4.2.

The purpose of the pF measurement is to manage the irrigation of a crop, the irrigation threshold being different from one crop to another.

Our innovation: the monitoring of the pF in trufficulture

The results of research and experimentation projects conducted at INRAEInstitut National de la Recherche pour l’Agriculture, l’Alimentation et l’Environnement – of Nancy-Grand Est in truffle growing have demonstrated the crucial importance of water in the truffle production process.

The truffle, like any living organism, can thus find itself in real distress in periods of drought and in the absence of water.

The experiments conducted by François Le Tacon (1982), as well as today within the framework of the national experimentation program CULTURTRUF coordinated by Claude Murat (INRAE Research Engineer and co-founder of WETRUF) reveal that the irrigation threshold of a black truffle Tuber melanosporum is located at pF = 4

See our blog article Controlled watering in truffle fields: data from research

The use of probes is therefore strongly recommended to optimize water management for :
1. know when to start watering
2. know how much water to bring

Therefore, within the IAM laboratory – Tree-Microorganism Interactions – of INRAE, was undertaken between 2018 and 2019 the development of a tool to monitor the water potential (pF) of the soil by reading plaster probes.


The simplicity of the plaster probe system makes it an effective and very affordable device.
This innovation, based on a specific calibration, allows an accurate and direct reading of the pF, without the need for any conversion.

It is through the signature of an exploitation license on secret know-how that WETRUF could take in charge the commercial development of this tool, today proposed under the name of pF Tracer One TM.

Reasoned irrigation for optimized production

The project CULTURTRUF highlights the fact that truffle cultivation is naturally low in water consumption compared to other crops. The monitoring of the water potential of the soil during dry spells allows us to evaluate the water supply needed to water the truffle fields.

The production of truffles is thus optimized while guaranteeing a reasoned and controlled watering which is part of an ecological approach and preservation of the resource.

The different aspects of water management and irrigation techniques are the main themes addressed during our training sessions. Are you interested? Find here our training offers in trufficulture and our next sessions to come!

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