What is Mushroom Compost?

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Few things can amend your garden soil, like mushroom compost can.

It is probably the single best thing you can add to any garden’s soil, whether you’re planting vegetables, fruits, or mushrooms themselves.

But there’s a catch… Mushroom is not always the best choice.

And making this compost is not so easy either.

For that reason, we want to show you all the ins and outs of mushroom compost. From how it is made to how you can make it yourself, what it offers, and what you should or shouldn’t expect – we’ll SHOW YOU EVERYTHING.

Take a look below and learn!

What is Mushroom Compost?

What is Mushroom Compost?

When you read the name mushroom compost, the first three things that come to mind are:

  • It is compost made of mushroom
  • It composts to grow mushrooms
  • It is compost left from growing mushrooms

Well, the three apply, but it all depends.

The focus of mushroom compost is to be a highly fertilizing product, free of contaminating agents.

It should be ready to provide a high amount of nutrients to whatever you plant on it.

Having said that, due to its strength in killing contaminants, it’s often a very salty material, so it is not ideal for every plant.

That’s why it’s called mushroom compost because mushrooms tend to thrive on it (but not many other species). However, it’s not always the case.

Types of Mushroom Compost

To make it easier to understand, you can consider the different kinds of mushroom compost available.

Here’s what to consider:

#1. Mushroom Substrate

The word “mushroom substrate” refers to a type of compost SPECIFICALLY made to grow mushrooms in.

It’s also the most popular type, made of chicken manure, gypsum, or wheat straw (plus other optional ingredients).

Most often, manufacturers use a wheat straw. This straw is processed in water and chipped until the material turns almost dirt-like. Then it is placed in a large compost pile and left to rest for a few weeks. After the weeks have passed, the straw turns into a dark-brown material.

This dark material is then pasteurized, eliminating any trace of unwanted pathogens, weeds, or other contaminants. Here’s when the material is ready to be used for either growing mushrooms by inoculating spores or any other plant that prefers this kind of compost.

BY THE WAY: Other ingredients for this substrate include bedding straw, grape crushings, soybean meal, potash, ammonium nitrate, lime, cottonseed meal, canola meal, and urea.

#2. Leftover Mushroom Compost

When the mushroom substrate is already used, what’s left is called “spent compost.”

This compost is not less effective, but it doesn’t contain the same amount of nutrients. For that reason, it’s mainly used to amend garden soil or as a turf conditioner – but not to plant vegetables or mushrooms themselves.

In contrast with the substrate, this one is less salty and more friendly with plants. But given it has fewer nutrients, it is less likely to be effective for general growth.
Some spent mushroom composts are sterilized and re-made to add extra nutrients and remove contaminants. But most often, they’re just leftovers.

NOTE: Using spent mushroom compost may come with some surprises, like mushrooms growing seemingly out of nowhere.

#3. Alternative Mushroom Composts

Other types of residues from organic processes may also work as mushroom compost. This includes coffee grounds, hardwood dust, peat moss, coconut coir, vermiculite, and different kinds of manures.

Regardless of the ingredient (or mix), they often go through a pasteurization process that removes most pathogens and hostile agents.

Then, they’re left to compost, so the particles break down, and the nutrients are more readily available for other plants (or mushrooms).

This compost is then used on spent mushroom composts or as turf builder. Also, it works as general compost for most plants.

WHAT TO KNOW: The difference between this and the typical mushroom substrate is the strength of the mix. While it is rich in nutrients, it is not as rich as a substrate made with wheat straw.

How is Mushroom Compost Made?

How is Mushroom Compost Made?

We already went through a brief explanation of how different types of mushroom composts are made. But we weren’t truly specific.

To make it up, here’s a more detailed step-by-step process:

  • The first step is to pick the ingredients. For most composts, manufacturers use straw as the main structure. Then cottonseed meal and chicken manure add the nutrients.
  • But the straw is left to compost at first. This takes anywhere from 2 weeks to 5 weeks (the compost needs to heat up).
  • Then, the manure and nutrient-rich ingredients are added. Other ingredients may also be included. At this moment, the compost is heated up even more due to the bacteria multiplying (up to 160 degrees Fahrenheit). This process kills weeds, pathogens, and pests.
  • It is essential to turn or mix the compost at least once a day as this happens. The turning helps the compost pasteurize a lot more consistently.
  • The manure will start to gain structure. That means the manure becomes soil-like, making it more water-absorbing and easily mixed with other soils.
  • A little less than a month or so after the first pasteurization (bacteria growing and heating up), the compost becomes ready to be used.

This is the typical process of commercial compost. But in some cases, the compost needs to age up to 2 years before it’s ready. This mostly happens for high-quality manure that’s very expensive.

What is Mushroom Compost Used For and its Benefits?

What is Mushroom Compost For?

Now, such a complicated and confusing process should have a definite purpose.

What is this mushroom compost for?

Well, it depends. People use it for a wide array of things. Here are the most common:

#1. Growing Mushrooms

The most common type of compost, mushroom substrate, works as the perfect nutrient base for the mushroom spores.

As these spores don’t go through the usual growth process of most plants, they need highly nutritious and sterilized soils to grow.

Here’s where the ultra-processed and well-sterilized mushroom compost comes into play. The mycelium (mushroom spore) will have an easier time growing on it than in standard soils or composts.

#2. Amending Soils

Once the compost is used by the mushrooms (this takes about 1 or 2 months until the mycelium is exhausted), it can grow other things.

This compost is still rich but not as strong as a typical substrate. It can be used as manure for perennials, shrubs, and many trees.

Amending soils with mushroom compost tends to be a highly productive task, increasing nitrogen and potassium amounts exponentially.

#3. Increasing Soil Humidity

Not only does mushroom compost add extra nutrients and sterilization, but it also helps to add better soil absorption.

The water-holding capacity of most soils is increased with this compost. This results in higher nutrient absorption for most plants, as well as ideal environments for humid-loving species.

Other Benefits of Using Mushroom Compost

#4. Mulch for Perennials

Some plants don’t mind the strength of mushroom compost (substrate or spent). When used as mulch, it can help absorb water, keep pests away, and fertilize the soil a bit.

This also works for flower beds, vegetable gardens, and even shrubs or trees.

BE CAREFUL: This compost tends to be salty, so it may cause harm to some plants. These include camellias, azaleas, rhododendrons, and heathers.

#5. Turf Building

In yards that need a topdressing layer, a mix of mushroom compost could work as lawn fertilizer.

Due to its superior nutrient availability and sterilization, this compost works as a great fertilizer without adding unwanted weeds or pests.

WATCH OUT: If you use spent mushroom compost for turf-building, there’s a chance you’ll see mushrooms growing from time to time.

#6. Worm Bedding

If you’re looking to prepare your own compost with worms, you don’t have to start with only residues. Using spent mushroom compost could help you boost the process.

Adding this type of compost to your tumbler not only adds extra microorganisms but increases its bacteria, killing pathogens in the process.

How To Make Mushroom Compost? | DIY Guide

How To Make Mushroom Compost

You should have a better idea of what mush compost does and what it can be used for.

Let’s now teach you how to make mushroom compost. Here’s a comprehensive guide to follow:

  • Gather the Materials

The materials will depend on what you have available. The reality is, as long as you’re using something that gives the compost structure and nutrients, it really doesn’t matter much.

But as a general rule, you should use straw as the structure (this should be about 40%), a manure ingredient (at least 20% of the mix), and the rest with sterilized soil (the remaining 40%).

Once you have all these ingredients, mix them up in a pile. You can use a compost bin for the job if necessary. Any clean and sufficiently large container will work.

  • Let Ingredients Break Down

Now it’s time to let everything break down. In short words, this is the composting process.

Here, you should wait AT LEAST 2 weeks. In this process, all the bacteria will start to grow in the manure, the materials will break down into nutrients, and the entire mix will heat up.

If you can heat up the mix to 160 degrees or more, that will accelerate the process. Otherwise, it will likely reach that temperature by itself, killing bacteria, pathogens, and weeds.

  • Turning it Over

While the ingredients break down, you need to turn it over consistently.

The air that comes into the mix tends to help with the breakdown of the materials.

You can also add extra moisture by hosing down the mix. This helps with the breakdown even more.

  • Let it Cure

After 2-4 weeks of composting, the mix is ready to be cured.

What this means is taking the compost into a new pile. Then let it air out for at least 2 more weeks.

While this happens, the compost will slowly turn darker, almost black. It should gain a soil-like consistency, meaning the compost is practically ready.

HINT: If you aren’t growing mushrooms, you can use this substrate for turfs, vegetable gardens, and other uses that don’t require pasteurization or sterilization.

  • Pasteurize the Compost

If you want the compost for clean purposes like growing mushrooms, you need to pasteurize it.
In short words, you need to kill any remaining pathogens. This is what pasteurization does.

Luckily, this is an easy process. The general rule is to pour the dark compost into a mesh bag and submerge it into boiling water (without turning off the heat).

You should let the compost pasteurize in the boiling water for at least an hour. After that, most of the remaining contaminants have probably faltered away.

  • Sterilize the Compost

This process sanitizes the compost even further.

Here, you will need to cook the substrate material in a pressure cooker. The substrate should stay within the pressure cooker for no less than 2 and a half hours.

At 250 degrees Fahrenheit and no less than 15 PSI of pressure, the substrate will end up clean and ready to be used for mushroom growing.

BY THE WAY: Some people sterilize the compost with a bag, so everything gets purified at once.

  • Getting the Compost Ready

The composting process is done. You can now decide whether you want to keep the compost resting for further composting (1 or 2 more years) or use it right away.

This compost is now clean and ready for any purpose.

Frequently Asked Questions (FAQs)

Q1. Will mushroom compost burn plants?

Because mushroom compost tends to be high in salt content, it can cause mild to severe burns to plants. This often happens with fragile species, so be careful.

Q2. Is mushroom compost good for vegetable gardens?

Yes. Thanks to the high absorbing structure, mushroom compost tends to be a valuable addition to vegetable gardens. This only works, however, when used mildly, like a top dressing or additive.

To avoid soil issues in your vegetable garden, you should not use more than 50% compost in the mix. Otherwise, you’re likely to be left with extra-salty or soggy soil.

Q3. What plants don’t like mushroom compost?

Many plants will have a problem with the high soluble salt content from mushroom compost. These include

  • Rhododendrons
  • Blueberries
  • Camellias
  • Azaleas
  • Heathers

Also, be careful when using mushroom compost on seeds and seedlings. The salty composition may cause trouble with growth.

Q4. Is mushroom compost good for lawns?

Yes. Due to its high nitrogen content and sterilization, it tends to be ideal for promoting faster turf growth.

Q5. How much mushroom compost do I need?

The general rule is to add less than 50% of your garden soil as mushroom compost. In the case of potting soil, you’ll want to mix less than 25%.

Q6. Does mushroom compost smell?

Given it is a highly processed compost, the smell tends to be mild. Most of the time, it has a musty scent.

Q7. Is mushroom compost high in nitrogen?

Yes. It is slowly available nitrogen but high enough to help most plants grow.

Q8. What PH is mushroom compost?

Mushroom compost has a pH level of 6.6, making it an alkaline material.

Prepare Some Mushroom Compost NOW!

Learning what mushroom compost is and how to use it can be enormously helpful.

If you’re thinking of either a cleaner way to fertilize your garden or growing mushrooms at home, then this should be your first step.

So, what are you waiting to make that mushroom compost happen? Start making it now!

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