Application of spent mushroom compost enhances wheat yield but reduces mycorrhizal associations and grain nutrient concentration

Authors: Carrara, Joseph; SMITH, ANDREW - Rodale Institute; Heller, Wade

Submitted to: Mycorrhiza
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/19/2025
Publication Date: 11/25/2025
Citation: Carrara, J.E., Smith, A.H., Heller, W. 2025. Application of spent mushroom compost enhances wheat yield but reduces mycorrhizal associations and grain nutrient concentration. Mycorrhiza. 35(67). http://doi.org/10.1007/s00572-025-01235-2.
DOI: https://doi.org/10.1007/s00572-025-01235-2

Interpretive Summary: The development of farm management practices which reduce the reliance on agricultural chemical inputs and enhance soil ecosystem services are critical for the improvement of agricultural sustainability. Furthermore, these practices must meet our population’s growing crop production demands while maintaining or enhancing crop nutritional quality. Here we report the results of a field trial investigating the combination of soil amendment with spent mushroom compost, an organic byproduct of the edible mushroom industry, and supplemental inoculation with arbuscular mycorrhizal fungi (AMF), plus controls, to investigate the impacts of these two management practices separately and together on wheat grain yield and nutritional content. We found that spent mushroom compost application enhanced grain yield by 40%, but reduced mineral nutrient concentrations leading to a dilution effect of grain phosphorus, potassium and magnesium. Additionally, application of spent mushroom compost negatively impacted the root colonization level by AMF, which was not ameliorated by the AMF inoculation treatment. The impact on AMF colonization is significant since it is the function of these fungi to aid in soil mineral nutrient uptake by plants, and the mineral concentration reductions observed in our trial correlated with the mycorrhizal colonization level. This work highlights the importance of characterization of interactions between organic soil amendments and soil microbial communities, especially AMF, since nutritional quality deficiencies may be overshadowed by crop yield increases.

Technical Abstract: Developing management practices that enhance crop yield while maintaining soil health is the foremost objective of the regenerative agriculture movement. One avenue to achieve this goal is using biofertilizers and alternative soil amendments to supplement or replace agrichemicals. Here we report the results of a pairwise field trial of spring wheat (Triticum aestivum) wherein we investigated individual and combined impacts of inoculation with arbuscular mycorrhizal fungi (AMF) and a spent mushroom compost amendment (herein mushroom compost). The symbiotic relationship between AMF and plants has been demonstrated to benefit the yield and nutritional quality of many crops by enhancing access to mineral nutrients and water. Mushroom compost, consisting of the devitalized residual substrate following harvest of edible mushrooms, is a byproduct of the mushroom industry and is comprised of a variety of nutrient rich organic material inputs. Therefore, we hypothesized that mushroom compost would have synergistic effects with AMF inoculation on wheat production and nutrient uptake. Mushroom compost addition, regardless of AMF inoculation, enhanced grain yield by ~40%, but reduced AMF root colonization level by ~25-40%. Additionally, despite yield increases, mushroom compost addition reduced grain phosphorus (P), potassium (K), and magnesium (Mg) concentrations by ~10% and boron concentration by ~45%. In fact, grain P, K, and Mg concentrations were all correlated with mycorrhizal colonization level. These results suggest that while spent mushroom compost additions enhanced grain yield, this may have led to a mineral nutrient ‘dilution effect’ exacerbated by negative impacts on AMF and community composition.