What was it all about?

Mushroom growers rely on a consistent supply of high-quality compost to maintain the yield and quality of crops, yet the actual process of composting is not well understood, particularly in the Australian environment.

This project aimed to provide detail about the key microbes involved in mushroom composting and the specific successive changes that occur. Eventually this knowledge could be used to develop a test that growers use to assess compost quality.

Traditionally, wheat straw and poultry manure are used to develop mushroom compost, but with fluctuations in the availability of these materials it was important to find if alternative materials can work just as well.

Researchers began by reviewing the literature on compost sources and quality, the enzyme activity of soil microbes that break down the substrate, supplements available to boost composting and any commercially practical tests for quality.

Traditional commercial composting materials and methods were trialled and samples were taken to identify physical, chemical and biological characteristics, such as carbon and nitrogen content, at different times through the composting and cropping process. These measurements were then correlated with mushroom crop yield.

The study was the most detailed molecular study yet undertaken of the mushroom composting process. It found that over 30,000 microbes were involved in a standard composting run, with rapid successive changes in both the bacterial and fungal populations. Many of the microbes had not been identified previously. It also characterized the biological activity of these microbes, and the chemical and other changes occurring in the compost throughout the process.

Further research is needed to investigate possible alternative compost materials, and the effects of adding particular organisms to promote reliable composting of alternative feedstocks.