Peat use in horticulture is associated with a large ecological footprint. Peat is the predominant growing media in Europe. Modern cropping systems rely heavily on dynamic interactions of the crop with the microorganisms in the growing media and yet, in the search for sustainable peat-alternatives, the microbiome of the growing media has often been ignored. In mushroom cultivation, peat is a prime determinant of productivity, in the form of a casing soil which supplies beneficial microbes. In this study we describe the microbial composition, interactions, and activity of four circular substrates used to proportionally replace peat in mushroom growing media. We also evaluate various physico-chemical characteristics of the peat-alternatives. We characterize the impact of sanitary pre-treatments such as steaming and acidification on the microbiome as well as the agronomical performance of the peat-reduced growing media. We found that grass fibres from agricultural residue streams, peat-moss farmed in degraded peatlands, and spent casing soil recycled from previous cultivation cycles can be used to successfully replace peat in mushroom growing media. Peat moss and spent casing were expectedly similar to peat in physical, chemical, and microbiological properties. However, the grass fibres had unique characteristics, such as high organic matter content, low water holding capacity and a diverse and competitive microbiome. Pre-treatment of the substrates by acidification and steaming significantly affected the microbiome, and reduced the presence of pests, pathogens and competitive fungi in the peat-reduced media. Strong trade-offs existed between the productivity and disease pressure in the circular cropping system, which are also governed by the microbial composition of the growing media. Knowledge on the accessibility, sustainability, and economic viability of these peat-alternatives will further determine the transition away from peat use and towards sustainable growing media.

园艺中的泥炭使用与巨大的生态足迹有关。泥炭是欧洲主要的生长介质。现代种植系统严重依赖作物与生长介质中微生物的动态相互作用，然而，在寻找可持续的泥炭替代品时，生长介质的微生物群落经常被忽视。在蘑菇种植中，泥炭是生产力的主要决定因素，以提供有益微生物的外壳土壤的形式存在。在这项研究中，我们描述了用于按比例替代蘑菇生长介质中泥炭的四种圆形基质的微生物组成、相互作用和活性。我们还评估了泥炭替代品的各种理化特性。我们描述了卫生预处理（如蒸汽和酸化）对微生物群的影响以及泥炭减少的生长介质的农艺性能。我们发现，来自农业残留物流的草纤维、退化泥炭地中种植的泥炭苔藓以及从以前的种植周期回收的用过的土壤可以成功地替代蘑菇生长介质中的泥炭。泥炭苔藓和废肠衣在物理、化学和微生物特性方面与泥炭相似。然而，草纤维具有独特的特性，例如有机质含量高、持水能力低以及微生物群落的多样性和竞争性。通过酸化和汽蒸对基质进行预处理显着影响了微生物组，并减少了害虫的存在，泥炭减少培养基中的病原体和竞争性真菌。在循环种植系统中，生产力和疾病压力之间存在很强的权衡，这也受生长介质的微生物组成的控制。对这些泥炭替代品的可及性、可持续性和经济可行性的了解将进一步决定从泥炭使用向可持续生长介质的过渡。