One of the most practical lectures at the last conference in Cahors was the one about irrigation in black truffle orchards done by Carlos Colinas. For the first time we get some specific data about it. Congrats to the whole team!
They already published a work where they showed as the first years for Quercus ilex to water 50% of potential evapotranspiration increased black truffle mycorrhization in your trees. This 50% equals to a water potential from -1,5 MPa and -o,35 MPa.
In a 22 years old evergreen oak plantation in Teruel they set 3 watering regimes. This is 32 l/m2 every 2-3-5 weeks and they harvested more truffles when watering every 2 weeks.
Results show how it is better to do not leave water potential to drop below -1 MPa for more than one week during the summer.
During the questions and discussion after Colinas speech, Gilberto Bragato made a quite interesting appreciation: he said that water potential is directly related to soil pore sizes, so some water potential made possible to plant roots to absorb water but not to small fungal mycelium or bacteria that may be 3microns diameter…
If anyone interested just found this table with the relations:
Here you can see another unit, the water potential (pF) that was as well used by Le Tacon, who found that when pF3 or pF4 no truffles fruit.
BTW, now that we are in Tuber magnatum season, Gilberto Bragato just made a reiew of soil characteristics for this truffle. See reference at the bottom.
As a conclusion for the mycorrhizae it looks that a dry “window” at mid summer may be good, but for truffle fruiting this research shows that a stress period in summer is no good at all.
Cheers,
Marcos S. Morcillo
References:
Oliach, D., Fischer, C. R., Colinas, C. (2016). Soil water potential relation to truffle productivity. In: Abstract book of The eighth international workshop on edible mycorrhizal mushrooms (IWEMM8). Oral presentation. 10-17 october 2016, Cahors, France.
Le Tacon F, Delmas J, Gleyze R, Bouchard D (1982) Influence du régime hydrique du sol et de la fertilisation sur la fructification de la truffe noire du Perigord (Tuber melanosporum Vitt.) dans le Sud-Est de la France. Acta Oecol-Oec Appl 3:291–306
trufflefarming 
Great article – thanks Marcos
Great article Marcos – really helpful information
what method do you prefer for measuring the soil water
Thanks Marie,
maybe pF is a better measure, but most probes give us data in kPa or %.
Marcos bonjour, Bonne année remplie de santé et de joie. Question: Dans un 22 ans plantation de chênes verts à Teruel ils ont mis 3 régimes d’arrosage. Ceci est 32 l / m2 toutes les semaines 2-3-5 et ils récolté plus truffes lors de l’arrosage toutes les 2 semaines.De quelle nature est le sol et la T° C en journée et la nuit ????
Bon nuit Vincent 🙂
yes, they saw that watering every two weeks they harvested a lot more truffles! This is keeping between -1 and 0 MPa.
for temperatures in Sarrión, check this link:
https://es.climate-data.org/location/246044/
This study was in loam soil, but in fact it does not matter here the “nature” or texture of soil, as the device to measure the water potencial (PST-55-15-SF Wescor water Potential Meter, in this case) gives you some data regardless of the soil texture.
cheers,
Marcos