Straw determines the structure and the nutrient value of compost. New straw is harder, which is why the pre-wet period is crucially important for good production.

Exciting: the first new straw

Last year the straw produced in Europe was bad quality. For this reason many composters are quickly switching over to using the new season’s straw. Making this change is always a rather exciting period. It’s important to open up the straw so the protective, waxy coating can be removed. This process is done by micro-organisms. Providing the right conditions for these micro-organisms to thrive obviously gives the best results!

What are the conditions for good micro-life?

– Water

Each sprig of straw must be wet. If part of the straw is still dry the right processes will fail to take place.

– Oxygen

Without sufficient oxygen, the micro-life will die. After the straw has been made wet, you have to add oxygen. Place the straw on top of an aerated floor or turn the pile of straw after a maximum of 25 hours using a loader.

– Nutrients

Straw contains enough nutrients. If only makes sense to add 30% of chicken manure in the winter when the weather is cold to encourage the temperature in the straw to rise.

The ideal process

If the straw is nice and wet and has enough oxygen you will see that the temperature increases to 50-60oC. This is the optimal temperature for the micro-life. Depending on the quality of the straw its colour will change from bright yellow to dull, dark yellow within 1 to 3 days. The straw feels soft to the touch and quickly absorbs water.


If the temperature exceeds 65oC, the micro-life will die. The colour of the compost will turn dark brown/black. The sprigs of straw will stay hard and not be broken down. This means that the mycelium will not develop in the straw but around it. No nutrients will be released and the result will be lower mushroom production.

So it’s not only oxygen, nutrients and water that are important – but the temperature too!

Bron: Mushroom Blog – Mark den Ouden

pre wett- mushroom growth


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