Mairead Kilpatrick and Ralph Noble discuss latest research findings
The UK and Irish mushroom industries are under severe competitive pressure from countries with lower production costs. Increasing the efficiency of compost production and mushroom cropping from the compost are critical in maintaining a viable British Isles industry. The mushroom composting industry is also under continuing environmental pressure to reduce the odours from composting sites.
Straw and compost quality
Wheat straw used for preparing mushroom compost is highly variable and this causes difficulties for compost manufacturers striving to produce consistent compost.
To better understand these differences and how they impact on the composting process, straw from 12 wheat cultivars (winter and spring) were selected for further investigation from four geographical sites in Britain and Northern Ireland.
In addition, crop husbandry protocols including the use (or not) of plant growth regulator and fungicides were included in the study.
The properties of straw were determined using Derivative Thermogravimetry (DTG), Near Infra-Red Spectroscopy (NIR), as well as more traditional analytical procedures measuring over 30 physio-chemical characteristics including soluble carbohydrate, soluble polyphenol and ash contents.
Analyses of these different batches of straw showed significant differences between wheat cultivars, sites, and applications of plant growth regulator, fungicides and nitrogen fertilizer.
Preliminary results have further shown that the different batches of straw composted under the same conditions can produce widely different compost performances in terms of spawn-running and mushroom cropping.
Site differences in straw appear to be greater than the effects of wheat cultivars, plant growth regulator and fungicides. Application of nitrogen fertilizer to wheat crops and storage of straw also had significant effects on the properties of the straw and its subsequent use in compost.
By the end of the project, it should be possible to specify guidelines for obtaining the best types of wheat straw for use in mushroom compost.
Faster spawn-running
Producing a well-colonised, spawn-run compost in as short a time as possible is an important objective.
The spawn-running of pasteurised (Phase II) compost obtained from 11 different composting sites was examined. A fall in compost pH gave an indication of spawn-run intensity but a more reliable method based on measuring the mushroom enzyme laccase has been developed.
There were correlations between the amount of laccase at the end of spawn-running of the composts, the rate of mycelial growth in the composts, and the subsequent mushroom yield.
The laccase enzyme test is enabling the important physical and chemical characteristics of compost in terms of spawn-running to be determined. The project is also examining whether spawn-running of a prepared compost can be manipulated e.g. by compost spawning methods, compost filling weight and pressure, and different supplements.
Recycled 'Goody' water
Goody water can be a potent source of odour on composting sites and can contribute to subsequent composting odours.
Chemical analysis has shown that a complex cocktail of compounds including sulphides, amino acids and fatty acids produces the odour. However, measuring the redox potential and dry matter (solids) content can give an indication of the likely odour.
Wide ranges in redox potential have been found between goody water samples taken from 11 different commercial sites. The project is identifying which water treatment methods result in the least odorous goody water, and the most appropriate remedial action to be taken.
Analyses have also shown that goody water is a highly variable compost ingredient with wide ranges in dry matter content, pH and conductivity (dissolved salts). Better quality goody water could therefore not only lead to reduced odours but also to more consistent compost quality.
Project profile
M 3e Improving the efficiency and environmental impact of mushroom composting
HortLink Reference Number: HL 0163
Project leader: Professor Ralph Noble, Warwick HRI
Participants:
Horticultural Development Council
Agricultural Supply Co Ltd
Carbury Mushrooms Ltd
Casella Eti
Custom Compost Ltd
Drinkwaters Mushrooms Ltd
Greenhill Compost Ltd
JA Gooding Ltd
J Rothwell Ltd
JEOL (UK) Ltd
Institute of Grassland and Environmental Research (IGER)
6/29/2011 4:13:41 PM I would be interested in finding out more about the laccase test that was performed and the methods employed in testing for laccase. Siobhan McGinnity, Monaghan Mushrooms
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