What is Mushroom Compost?

_{This post was orriginally published 3/20/20 and updated on 6/14/21.}

Mushroom compost has many benefits for your plants and overall soil health. It’s a great ammendment to your garden and adds many beneficial nutritents. Use with caution, however, as it can be harmful to some plants. All-in-all, mushroom compost is excellent for your garden when mixed throughly with your garden soil.

What does mushroom compost do?

When used as an amendment, it provides a readily-available source of organic material to soil, which increases water capacity, microbial activity, and soil temperature. It also improves soil structure and amends clay-like soils over time. It is great for adding essential nutrients and micro-organisms to vegetable garden beds, as well as around perennials, trees and shrubs. Generally, the nutrients in a batch of this compost contains 1-2% nitrogen, 0.2% phosphorus and 1.3% potassium.

What’s the process of making mushroom compost like?

After mushroom farmers harvest a crop of mushrooms, they sell the soil that the mushrooms were growing in. This leftover soil is high in organic matter making it desirable for use as a soil amendment (PSU).

Since mushrooms are fungi, they do not have chlorophyll and cannot produce carbohydrates by photosynthesis like plants can. Therefore, the substrate that mushrooms grow in must have a large supply of all essential nutrients for mushroom growth. Commercially, the mixes vary from grower to grower; although, most substrate mixes usually consist of chopped straw, poultry and horse manure, gypsum, nitrogen-containing compounds, and water. The leftover soil is able to be given a new life in organic farming as an amendment to improve water infiltration, holding capacity, permeability, and aeration.

As a result of the high temperatures associated with the composting and pasteurization processes, mushroom compost is free of pests and weed seeds.

Mushroom compost contains an abundance of salt and unstable organic material. Due to this, it should be aged for about two years before applying. This allows for leaching of organic solutes and decomposition of organic matter. Most mushroom compost you can buy at retail locations has already been aged, so you don’t have to worry about doing this yourself.

How should mushroom compost be used?

For flower beds and vegetable gardens, top-dress with the compost or till in about three inches of the compost into the top six inches of fairly dry garden soil. For containerized plants, it should only make up about one-quarter of the volume of soil in the container.

However, mushroom compost isn’t for every plant because it is rich in soluble salts and other nutrients. These can kill germinating seeds and harm salt-sensitive plants including rhododendrons, azaleas, camellias, and other members of the heath family (OSU). It should also not be applied to young plants because they are particularly sensitive to high levels of salts and ammonium.

You can make compost tea to use as a liquid fertilizer/ foliar spray by mixing one part compost with four parts water. The “tea” will have an abundance of beneficial microorganisms, including bacteria, fungi, protozoa and nematodes. This concoction will help your plant survive any pest attacks or disease.

Compared to traditional mineral fertilizers

Mushroom compost is more expensive than mineral fertilizers in terms of the nutrient content per unit weight, but it provides many benefits that mineral fertilizers cannot. When applied, it improves the biological, physical and chemical characteristics of the soil (Uzun). Nutrients from it are slowly released over a longer period of time. This means plants can use them more effectively than traditional mineral fertilizers.

What we offer

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We offer bulk mushroom compost throughout the main gardening season, which we get from a small grower in Pennsylvania. You can purchase the compost by itself or as a mixture of topsoil and compost, the Jack Frost mix. This is a great option for filling raised beds for example. And for those that might need a smaller quantity, we also offer a bagged option from Daddy Pete’s Plant Pleasers . Both have been properly aged to avoid damage to your plants. We usually recommend to use these products in vegetable and fruit gardens.

Sources

https://extension.oregonstate.edu/news/what-mushroom-compost

https://extension.psu.edu/spent-mushroom-substrate

https://pdfs.semanticscholar.org/ab0d/8b48407d73fe36b1bd275b1187add41d522b.pdf