Closing the Mushroom Production Loop: Evaluating Soil Microbe Changes Following Field Application of Compost Inoculated with Spent Mushroom Substrate

Project Overview

Project Type: Partnership
Funds awarded in 2022: $24,712.00
Projected End Date: 12/31/2023
Grant Recipient: NOFA/Mass
Region: Northeast
State: Massachusetts
Project Leader:

Information Products


  • Miscellaneous: mushrooms


  • Crop Production: application rate management, biological inoculants
  • Education and Training: on-farm/ranch research, youth education
  • Production Systems: organic agriculture
  • Soil Management: composting, green manures, organic matter, soil analysis, soil chemistry, soil microbiology, soil quality/health

    Proposal abstract:

    Spent mushroom substrate (SMS), a byproduct of mushroom production, is nutrient-rich and abundant with known benefits as a soil amendment. However, it is infrequently used by farmers in the Northeastern farming community, and mushroom producers are left with an unsustainable surplus of SMS. The goals of this project are to create a sustainable outlet for the existing SMS surplus in the Northeast while also improving the soil health and microbial communities of vegetable farms. To address these goals, we will evaluate SMS as a fungal inoculant in finished compost and the impact of the SMS-inoculated compost on soil health parameters, including microbial activity, following application to production beds. Soils amended with SMS-inoculated compost will be evaluated for up to 12 months following application to assess the impacts of this amendment on soil health and crop production. Positive field trial results will support the use of SMS as a compost inoculant, and we will work within the farming community to share these benefits and make connections between mushroom and vegetable farmers. Our planned outreach will educate farmers and gardeners about mushroom production and the value of SMS as a soil amendment through education events including two on-farm events, a podcast, conference workshop, and project reports shared within the farming and gardening community.

    Project objectives from proposal:

    This project seeks to accomplish the following objectives:

    • Evaluate which ratio of compost:spent mushroom substrate (SMS) best increases the microbiological activity of finished compost over the duration of a 14d period, and
    • Determine whether the application of compost inoculated with SMS improves soil health characteristics including soil microbial activity, active carbon, bulk density, and soil hardness when applied to vegetable production systems.

    Positive findings from these objectives will provide the following benefits to farmers:

    • Provide mushroom farmers with a use for a production byproduct, sustainably closing the production loop
    • Offer vegetable farmers an opportunity to increase soil fungal activity and soil health characteristics, likely leading to improved crop growth and production without requiring much additional time or a change in management

    If this project is successful, we envision developing partnerships between specialty mushroom and vegetable farms in the Northeast to create a continual cycle of SMS utilization in compost. The compost inoculation method is a straightforward and time-efficient way to increase microbial communities in an amendment vegetable farmers are already using, making it easy for this to be widely adopted and successful within the farming community.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.