When straw was chopped at the start of composting, the bulk density of straw-based mushroom compost increased and there was a corresponding reduction in volume compared with normal (unchopped) straw. Prolonging the duration of composting also increased bulk density and reduced the weight of compost produced per tonne of straw.
Mushroom yields per compost volume increased with increasing bulk density and production efficiency, i.e. the weight of mushrooms per unit compost dry matter was not significantly different between composts.
Bulk density and porosity of mushroom composts and the relative effects of bulk density and depth of compost on mushroom yields are discussed.