If one wants to start a discussion with a grower (or with a consultant), start talking about watering.
How much, when and what watering method.

To make any sense though, you first have to define the period. There is watering on casing soil and watering over mushrooms and between flushes.
This blog is about watering on the casing soil during the incubation period. The water given in that period is to bring the casing soil up to the maximum moisture level and to keep the compost at the right moisture.
A good phase 3 compost at the moment of casing will be around 60% in moisture. For white strains that can be up to 3% higher, brown strains prefer 1 or 2% drier. It is not possible to bring the compost to a much higher moisture level by watering it after filling. It is possible to give water into the compost but that will be free water which has to disappear during the fructification period.
2 up to 4 litres of water can be given into the compost at filling or later but that should be the maximum. Even if it is necessary to cool the compost. This can better be done by giving water into the casing and let it evaporate with fresh air and circulation.

Casing soil itself can handle up to 7 litres per m² plus the water that was originally in the casing. To be sure, we talk about a casing containing white and black peat.
More than 7 litres will evaporate, go into the compost or down the drain.
Considering that the evaporation can be around 2 litres per m² per day, the loss with evaporation is about 10 litres. If you count the loss of dripping, the water staying in the compost and the evaporation you come to a figure of about 25 litres of water. In practical situations this means a total amount of water between 20 and 30 litres average. Depending on the farm and the time of the year. Growing drier often means a loss of production and growing a lot wetter means problems in growing, mainly in the outgrow of mushrooms.
Another thing to watch for is the watering method. Make sure that the pressure of the water onto the casing is not too high. Too many times I see a casing with a damaged surface which will give problems in the evaporation.

Every system has a different pressure and if you are not sure, ask the manufacturer. Regularly cleaning of the nozzles is something will help maintaining the right pressure and the right adjustment of the watering trees, looking at distance and height according to the casing level.
Keep watering but do not take it over the top!!