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Spent casing, Sphagnum moss, grass fibers, and green compost as peat alternatives in casing soils for Agaricus bisporus cultivation

Summary

Researchers tested alternative materials to replace peat in the soil layer used for growing button mushrooms. They found that moss and compost could replace up to 75% of peat without reducing mushroom yields, though grass-based materials were less effective. The study shows it is possible to move toward more sustainable mushroom farming while maintaining productivity and controlling plant diseases.

Background

Peat is traditionally used in mushroom cultivation casing soils due to its excellent physical and chemical properties, but its extraction threatens important peatland ecosystems. Alternative materials need to be identified to replace peat while maintaining mushroom productivity and disease suppressiveness.

Objective

To determine the maximum percentage of peat that can be replaced by alternative materials (spent casing, Sphagnum moss, grass fibers, and green compost) in casing soils for Agaricus bisporus cultivation without compromising yield or disease control, and to evaluate combinations of these materials.

Results

Peat could be replaced by up to 75% of Sphagnum moss or green compost without significant yield reduction, while spent casing and grass A allowed up to 50% replacement. Unsteamed grass B caused significant yield loss at 30% replacement and high blotch incidence, which was mitigated by steaming. Moisture content at low suction pressure was the strongest predictor of yield. Mixed casing soils showed more consistent yields between flushes.

Conclusion

Sphagnum moss and green compost are viable peat alternatives, capable of replacing up to 75% of peat. Steaming of grass components prevents disease while affecting yield variably. All tested materials contained heavy metals and pesticide residues below legal limits. Physico-chemical properties alone do not predict disease incidence; microbial composition plays an important role.
  • Published in:Scientific Reports,
  • Study Type:Experimental Study,
  • Source: PMID: 41131166, DOI: 10.1038/s41598-025-20453-4
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