The video shows the “third flush” as it’s known in the mushroom farming world. The following explanation is the growing process, with a few secrets left out!
The preparation prior to going into the growing rooms involves mixing manure with mushroom spores / seeds. The quality of the manure is extremely important and is part of the process. The farmer will have sourced for many years from quality suppliers.
In the video you can see a 20cm bottom layer of manure that has the spores mixed in, this is the whiter looking layer. Sat on top of that is a 5cm layer of peat that is there to stimulate the mushroom spores in the manure to grow, so a good quality peat is very important. This mixture is laid out on the 20 metre shelves and made completely flat. The mixture is then sprayed with water and kept wet with as low a level of oxygen as possible. The temperature of the room is around 22°C for this part of the process which allows for maximum development of the spores. No mushroom will be visible at this stage.
All the important factors are then changed for the second flush. The temperature will be bought down to around 18°C and the level of oxygen will be increased. The combination of these two factors vastly increases the development of the spores and tiny heads start to poke up through the peat. These are only between 1-5mm in size.
This is the exciting part that makes it all worthwhile. At this point the changing of the temperature and humidity makes all the difference to the size of the mushroom grown. Keeping the air temperature and humidity low means more buttons will grow and they will be smaller. Doing the opposite and keeping the temperature and humidity high will result in fewer buttons but more space for them to grow, resulting in larger caps. The buttons are now ready for harvesting.
In the video the buttons are 1 day away from being harvested!
The whole process from laying the manure and peat mixture to the day of harvest is around 21 days.