Imagine the third picking day of a first flush. In the morning the pickers are picking a beautiful mushroom. Around noon the mushrooms are starting to lose colour and 3 hours later they start growing like mad. Stems are stretching and caps are getting soft.
Does that sound familiar?
In that case look at the casing. If you start checking the casing it is very well possible that it is getting warmer. The differential between ambient temperature and casing temperature is gone. This means that the evaporation has almost or completely stopped. In other words: the casing soil is too dry.
Watering at that moment is too late. If water is applied at this moment the mushrooms will lose the colour completely and bacterial blotch is the next problem.
To solve that problem the grower has to look at the next room where the next flush is coming. In the last days of outgrow water can be given on mushrooms that have the size between a pea and a cherry. Generally, that is about 3 days before the start of the harvest of the first flush. The amount of water can be around 2 litres per m².
Just one watering can be enough to solve this problem.
But only if the rest of the circumstances are okay. A good open and heavy casing soil which can hold that water.
And good selective picking so the outgrow of the flush during the harvest is more gradual and not explosive.
It is possible to detect the moment when the casing is drying out by using an infrared thermometer. If the casing soil temperature is getting up, the casing dries out. The right watering moment is just before that point.