Optimising nitrogen transformations in mushroom production (MU17004)
What’s it all about?
This project will ultimately help mushroom growers to optimise the rate and timing of nitrogen additions, to achieve maximum yield and nutritional value.
The project team are currently exploring the fate of nitrogen used in mushroom production and composting, including developing a better understanding the microorganisms that are involved in transforming the nitrogen that is added throughout the mushroom production process into other forms. They are also looking at ways and timings to maximise nitrogen use efficiency and promote nitrogen retention for composting, and more. A best practice guide for growers will be produced out of the project findings.
Since the last project update, a survey of 10 Australian mushroom composting facilities across four States has been completed. It included a comparison of composting management processes and compost bacterial activity. The results delivered initial insights to inform the selection of compost yards for further nitrogen management analysis.
The survey revealed that an average of 10 per cent of input nitrogen is incorporated into the mushroom crop, and about 20 per cent of the total is lost as leachate or nitrogen-containing gases. Nitrogen losses also occur from the compost and casing during cropping. To better understand this process, two cropping trials have been established in the Marsh-Lawson Mushroom Unit. Analysis has unfortunately been delayed due to Covid-19 impacts.
The team have isolated specific microorganisms from high temperature composts, with the dominant strains identified by DNA sequencing and characterised. Interactions between the two main compost fungi (Mycothermus thermophilus and Agaricus bisporus) and the dominant Phase 2 bacterial taxa (Pseudoxanthomonas spp) have been examined in more detail. Due to the high relevance of these bacterial taxa, their entire genetic sequence has been determined, with analysis of their functional capabilities ongoing.
The compost isolate collection contains 175 isolates of 58 different species. This is now sufficient for the design of potential compost inoculation treatments aimed at optimising the composting process.
The reporting period coincided with Covid-19 related work and travel restrictions, resulting in considerable disruption to research progress. The team will continue to share results with industry as opportunities become available.
The project team commenced work in January 2019 and have already isolated and characterised a substantial collection of bacterial strains taken from a range of Australian compost yards in New South Wales, Victoria, South Australia and Tasmania. These samples represent the dominant cultivable bacteria in composts and will underpin the rest of the project.
Many of the most prevalent strains identified were very similar, despite coming from different geographical areas, confirming the conserved biological nature of mushroom composting across Australia.
Analysis of the composts revealed that many of the dominant species have not yet been captured in the strain collection. These are now being targeted using specifically designed growth media and selective conditions.
A detailed survey regarding current nitrogen management by Australian composters was started, with field trips to facilities in Victoria, New South Wales and South Australia, and visits planned to Queensland. The results of this confidential survey will be used to identify composting yards that represent the diversity of processes in the Australian industry, informing the project’s detailed nitrogen balance studies.
Read an overview of the project in this article, Optimisation of nitrogen use in mushroom production, published on pages 34-35 in the spring 2019 edition of the Australian Mushrooms Journal.
This project is a strategic levy investment in the Hort Innovation Mushroom Fund