Developing a New, Improved & More Sustainable Mushroom Casing Neutralisation Process

Project No: 158160/RR

Harte Peat Ltd.

Project Leader: Ross Mac Donald

This project was devised by Harte Peat Ltd. and supported by Enterprise Ireland and supported by the European Regional Development Fund.

The project objective was to research and develop alternative methods of neutralizing peat in the manufacture of mushroom casing with the objective of reducing unit costs, improving pH control, fibre, structure, water retention and consistency, while not having any adverse effects on the yield, quality or growing cycle of our commercial mushroom grower customers.

The project is completed and has been a success, all the stages from devising project, lab trials, commercial trials and customer acceptance trials have been undertaken.

Harte Peat Ltd. have an economically viable, sustainable liming agent that has the potential for cost savings, improved pH control, with no adverse effects on the physical parameters of the casing.

The report from the trials compiled by Ralph Noble of East Malling Services states that the Hydrated lime mix casing works as well as the Sugar Beet Lime/Ground limestone mix and with satisfactory feedback from all the trials and market acceptance from selected farms we sent the hydrated casing to, both on the performance of the casing regarding yield and the low incidence of disease in the relevant crops.

Project Title: Comparison of lime sources used in mushroom casing: Harte Peat Ltd for Enterprise Ireland project This project was devised by Harte Peat Ltd. and supported by Enterprise Ireland and supported by the European Regional Development Fund. The 20 month project which involved Lab field and commercial trials is completed and has been a success, all the stages from devising project, lab trials, commercial trials and customer acceptance trials have been undertaken. Harte Peat Ltd. have an economically viable , sustainable liming agent that has the potential for cost savings, improved pH control, with no adverse effects on the physical parameters of the casing. The report from the trials compiled by Ralph Noble of East Malling Services states that the Hydrated lime mix casing works as well as the Sugar Beet Lime/Ground limestone mix and with satisfactory feedback from all the trials and market acceptance from selected farms we sent the hydrated casing to, both on the performance of the casing regarding yield and the low incidence of disease in the relevant crops.

Summary

The aim of this project was to investigate the use of hydrated lime as a replacement for sugar beet lime and ground limestone in mushroom casing. Casing blends were first prepared and tested in small-scale mushroom cropping experiments. The best blends were then prepared by Harte Peat Ltd and tested in three commercial-scale mushroom cropping experiments.

Mixing hydrated lime with dry peat (50 litres) before addition to wet peat (3 kg hydrated lime per cubic metre peat) resulted in a uniform casing pH. Substitution of sugar beet lime (SBL) and ground limestone in casing, either partially or completely with hydrated lime did not affect mushroom yield, quality or bacterial blotch incidence. Mushroom dry matter content was slightly lower when SBL and ground limestone was replaced with hydrated lime in casing. Casing prepared with SBL and ground limestone had a slightly lower gravimetric moisture content and slightly higher electrical conductivity than casing prepared with hydrated lime; this may explain the small difference in mushroom dry matter content. Casing pH, bulk density, and volumetric water and air holding characteristics were unaffected by the lime sources (SBL, ground limestone and/or hydrated lime). Addition of 3 g hydrated lime per litre Harte peat (equivalent to 3 kg/m3) resulted in a casing pH of 8. This fell to 7.4-7.5 at the time of use. A slightly higher rate of hydrated lime (3.5 kg/m3) is therefore recommended.

Mushroom yields were not statistically different between lime source treatments A (SBL + Ground limestone), B (SBL + Hydrated lime) and C (Hydrated lime)

Conclusions

1. Mixing hydrated lime with dry peat (50 litres) before addition to wet peat (3 kg per cubic metre peat) resulted in a uniform casing pH.
2. Substitution of sugar beet lime (SBL) and ground limestone in casing, either partially or completely, with hydrated lime did not affect mushroom yield, quality or bacterial blotch incidence.
3. Mushroom dry matter content was slightly lower when SBL was replaced with hydrated lime in casing.
4. Casing prepared with SBL and ground limestone had a slightly lower gravimetric moisture content and slightly higher electrical conductivity than casing prepared with hydrated lime; this may explain the small difference in mushroom dry matter content.
5. Casing pH, bulk density, and volumetric water and air holding characteristics were unaffected by the lime sources (SBL, ground limestone and/or hydrated lime).
6. Addition of 3 g hydrated lime per litre Harte peat (equivalent to 3 kg/m3) resulted in a casing pH of 8. This fell to 7.4-7.5 at the time of use. A slightly higher rate of hydrated lime (3.5 kg/m3) is therefore recommended.