What is the Dutch 'Champost' in English?

Answer 1

'Spent mushroom compost' is an English equivalent of 'Champost'.

This kind of compost is what's left over from the production of mushrooms. It tends to be a nutritious combination of dried blood, ground chalk, horse manure, and wheat straw. Such an offering gives the soil and the soil food web a healthy supply of nitrogen, phosphorus, potassium, and trace elements.

But there may be two drawbacks with spent mushroom compost. One is the presence of whatever may have been used to treat fungus gnats. The other is the compost's possible sweetening or alkalizing effect on the soil's pH. The first may be a legitimate concern, depending upon the supplier. The second tends to be less of a concern. In truth, it takes quite a bit of sweetening to change soil acidity/neutrality/alkalinity.