With mycelium growth in tunnels the compost disappears after inoculation for at least two weeks behind closed doors. The compost activity and increasing pressure give a certain indication of the extent of incubation. However, the final results of incubation can only be judged when the compost is delivered. If the tunnel company only supplies inoculated compost, it is often impossible to estimate how well and how quickly the compost is incubated.
A simple check can give far more information about what happens during the mycelium growth phase in the tunnels. Take an empty clear 1½ litre plastic bottle and cut away the upper part. Fill the base with a 3-centimetre thick layer of spawn and cover this with a 12-centimetre layer of compost. Replace the upper part of the bottle upside down on the lower half. Then place the bottle in an ambient temperature of around 23-25 degrees Celsius. Within a few days you should be able to see the mycelium growing up into the compost from the spawn grains.
After about a week the mycelium should be halfway and in the space of two weeks the mycelium should have reached the top of the bottle. If you take a sample like this each week, it's easy to see when mycelium growth in the tunnel is stagnating and take action in time.
Con Hermans, AdVisie ‘The mushroom cultivation advisors’