The significance of thermophilic fungi in mushroom compost preparation

When mixtures of wheat straw and organic nitrogen supplements were composted at 40° C in a simple small-scale, 1-phase composting system, initial inoculation with several species of thermophilic fungi resulted in a large improvement in the suitability of the composts for the cultivated mushroom. Ammonia levels fell rapidly and the ability of the composts to support competitor fungi was reduced. The species Torula thermophila, Cooney and Emerson, was particularly effective in bringing about these changes, and showed considerable potential as a rapid-composting organism. Composting was also accelerated by using a supplement such as sewage sludge, which had a low potential for producing ammonia. The inoculation of thermophilic fungi into conventional mushroom compost at the start of Phase II had little beneficial effect, probably because an adequate microflora of suitable composting organisms, including thermophilic fungi, was already present. If this microflora was first severely reduced, then a large effect from inoculating thermophilic fungi could be demonstrated. The results also indicated that the toxicity of ammonia to micro-organisms other than the mushroom could be an important feature of mushroom composting.