Is Mushroom Compost Good for a Vegetable Garden? (Answered)

Mushroom compost is the leftover substrate from mushroom farming. It includes remnant and essential nutrients that can enrich the vegetable garden.

Though the name suggests, mushroom compost doesn’t include mushrooms in it. It is the leftover medium from mushroom farms. For every 1 kg of mushrooms, 5kg of spent mushroom compost is left.

Researchers recommended reusing mushroom compost to fertilize plants to reduce the impact on the global environment.

The leftover substrate is filled with nutrients that can’t be ignored.

Nutritional needs of plants differ; to avoid over-fertilization, you must ensure that mushroom compost is good for your vegetable plants.

Mushroom compost consists of different agricultural materials like 60-70 % of straw, 28-34% of manure, and 2-4.5% of gypsum. These nutrients have high levels of essential nutrients that can benefit vegetables.

But, if mushroom farmers use chemical pesticides, which the majority of commercially produced mushrooms do, it can also include some chemical residues in your organic vegetable garden.

In this case, you may want to use something other than mushroom compost to fertilize vegetable plants. 

Apart from this, peat moss, potash, urea, ammonium nitrate, ground corn cobs, hay, and canola meal can be found in the mixture of spent mushrooms.

The nutritional ability of mushroom compost varies depending on the material used during mushroom farming.

What is Mushroom Compost?

It is a by-product of mushroom farming, which includes hay, straw, manure, peat moss, and other organic substances.

The growing medium is pasteurized to kill any weeds and fungal growth.

As the leftovers from mushroom farms are low in nitrogen, you must add fresh manure to the compost to make it rich in essential nutrients.

You can make your mushroom compost at home. Later in this article, I’ll discuss a step-by-step guide to preparing mushroom compost.

Is Mushroom Compost Good for a Vegetable Garden? 

Yes, mushroom compost is a rich source of organic matter and can be a great soil amendment.

A study conducted to determine the effect of spent mushroom compost on vegetable plants in a controlled environment concluded that adding mushroom compost increases vegetable yield. But it reduced germination time. (Source)

mushroom compost for vegetable garden

Adding mushroom compost can improve soil texture, aeration, and water retention ability.

Mushroom mycelium is similar to other plants’ root systems; it helps break down food compounds into plant-absorbable nutrients.

30 fresh mushroom compost samples were analysed to determine the nutritional content by researchers. Below are their findings.

  • Mushroom compost includes 25.86% organic matter that helps to retain moisture, improve soil texture, and increase microbial activity.
  • Essential nutrients like nitrogen (1.12%), phosphorus (0.28%), and potassium (1.04%) are housed in fresh mushroom compost.
  • In mushroom compost, secondary nutrients like magnesium and sodium and trace elements like copper, iron, manganese, zinc, molybdenum, and soluble salts are also found.

Depending on the farming material, nutrient composition may differ from crop to crop.

Vegetable plants are heavy feeders and need good primary nutrients, such as nitrogen, phosphorus, and potassium, found in mushroom compost.

Similarly, secondary elements needed to improve the plant’s ability to absorb nutrients are present in the mushroom substrate.

By this, can we conclude that mushroom compost is safe for vegetable plants?

Yes, but if the mushroom leftover you collected has a chemically incorporated pesticide or fungi, you might rethink adding it to your organic garden.

However, many anecdotal reports and researchers back the use of mushroom compost to enrich agricultural lands and raised beds.

But don’t rely on mushroom compost to fertilize your vegetable plants.

Besides being a slow-releasing fertilizer, it doesn’t include essential nutrients.

Benefits of Mushroom Compost

By now, you might know that mushroom compost isn’t the composted form of mushrooms.

Rather, it is the spent growing medium in which mushrooms are grown. It combines different things: straw, hay, horse manure, poultry litter, and other organic materials.

  • Improves microbial activity: Mushroom compost is already inoculated with fungal and microbial activity that can readily benefit your vegetable plants.
  • Soil texture is improved: Mushroom’s mycelium breaks down food sources and improves soil texture.
  • Increase water retention ability: You can improve the water retention ability of your growing medium by mulching mushroom compost.
  • Source of primary and secondary nutrients: Nitrogen, phosphorus, and potassium, along with calcium, magnesium, and other trace elements, are housed in mushroom compost, which can enrich your garden soil.
  • Organic Matter: Fresh mushroom compost has 25% organic matter that improves soil texture, increases microbial activity, and locks moisture for longer.
  • Slow-releasing fertilizer: It ensures the plant gets a continuous supply of nutrients.

Note: You shouldn’t rely on mushroom compost to supply nutrients for your plant. Also, you should know that using mushroom compost can reduce the pH of acidic soil.

How is Mushroom Compost Made?

If you’re a small mushroom grower, you can reuse the leftover substrate to enrich your vegetable garden.

Or you can get spent mushroom compost from farmers.

  • The nutritional ability of mushroom compost relies on a carefully selected blend of organic materials.
  • Materials like wheat straw, hay, corncobs, horse or poultry manure, gypsum, peat moss, soybean meal, or other organic matter are included in it. You should choose materials that break down quickly and provide the necessary nutrients.
  • Heat is essential in the mushroom composting process. Maintain composting pile temperature of more than 160F for a few days.
  • The heat helps to break down organic compounds and eliminate weeds and harmful pathogens.
  • During hot composting, you must turn the compost pile regularly to ensure aeration and facilitate decomposition.
  • Maintaining optimal moisture levels is important, as it contributes to the efficient decomposition of organic materials. It ensures the microbe gets ideal conditions to convert organic compounds to nutrients.
  • After nearly two weeks of hot composting, let the compost age and cure more.
  • Make a separate pile and let it sit for a couple of weeks. The compost will darken during this time, showing more breakdown and decomposition. The aim is not to start hot composting again but to encourage a slow breakdown and change.¬†
  • Unlike the hot compost pile, you don’t need to turn the secondary pile regularly.
  • Instead, keep it moist by watering it occasionally. When the secondary pile has finished transforming, your mushroom compost is ready.

You can use obtained mushroom compost to amend soil or mulch around the vegetable plants.

How to Use Mushroom Compost for Vegetables?

There are different ways to include nutrient-rich compost in your vegetable garden.

You can use it to mulch around veggies or include it as a soil amendment.

The slow-releasing fertilizer ensures the plant gets a consistent supply of nutrients.

However, nutrients in mushroom compost aren’t enough to fulfil plant needs. So, you must add nitrogen-rich manure or natural fertilizer to compensate for low nitrogen levels.

Note: Mushroom compost exhibits an alkaline nature. Vegetable plants that prefer acidic soil may not find it comfortable. To avoid nutritional impact, limit the usage of mushroom compost on acid-loving plants.

Research states that mushroom compost slows germination, but it increases yield.

So, I recommend adding mushroom compost as mulch around the adult vegetable plants.

Soil Amendment

Most vegetable plants prefer a well-drained growing medium. Adding mushroom compost can improve soil structure and benefit microbial activity in the garden soil.

Add 1/4th mushroom compost to 3/4th of potting soil mix.

Early spring is the best time to include spent mushroom compost in the garden. It allows enough time to break down organic compounds into easily absorbable nutrients.

Top dressing

Mushroom compost is a slow-releasing fertilizer that can be added as mulch around the vegetable plants.

While adding the compost, ensure you don’t overuse it or cover the foliage.

What vegetables, like mushroom compost?

Fresh mushroom compost has higher levels of soluble salts, which may impact the growth of certain plants.

So, it is important to know which vegetable plants like mushroom compost.

  • Tomatoes
  • Cabbage
  • Potatoes
  • Spinach
  • Bell peppers
  • Beets
  • Lettuce
  • Carrots
  • Peas
  • Kale
  • Sweet corn
  • Broccoli

The above-listed plants do well in mushroom compost, absorbing salts efficiently.

What Vegetables Do Not Like Mushroom Compost?

You must keep salt-sensitive, young plants and germinating seeds away from mushroom compost.

– John Hart of Oregon State University

The excess use of mushroom compost can kill the mentioned veggies and flowering plants.

  • Cucumbers
  • Celery
  • Blueberries
  • Beans
  • Camellias
  • Magnolias
  • Rhododendrons
  • Azaleas
  • Radishes

Is mushroom compost mulch good for vegetable gardens?

Yes, you can use spent mushroom compost as mulch around the plants.

The slow-releasing fertilizing ability of mushroom compost ensures the vegetable plant gets a continuous supply of nutrients.

Gardeners are aware that an excess of anything can be harmful to a plant’s health.

Limit mushroom compost use so that it won’t trigger nutritional imbalance.

What is Spent Mushroom? Can you use it to fertilize vegetable gardens?

Spent mushroom is the substrate or leftover growing medium of mushroom farming.

It includes different organic materials that improve your garden’s soil texture and water retention ability when added.

As it is rich in organic matter and essential nutrients, spent mushrooms can be used to fertilize vegetable plants.

Before adding spent mushroom compost (SMC) to the potting soil, you must consider a few factors like preferred soil pH, decomposition period, and mixing other organic amendments with SMC.

Mushroom Compost Vs. Manure: Which is Better for Vegetables?

Fresh cattle or poultry manure shouldn’t be used directly in vegetable gardens.

It is important to use manure cautiously due to its potential to harm crops with its content of pathogens and ammonia.

Manure should be decomposed before adding it to the garden.

Mushroom compost or manure?

The answer lies in the nutritional requirements of your garden.

If you’re looking for nitrogen-rich fertilizer, then opt for well-rotted manure.

However, mushroom compost benefits your garden soil, as mentioned already.

Important Tips While Using Mushroom Compost for Vegetable Garden

Not just mushroom compost; every time you fertilize your garden, it is important to conduct soil tests to determine its nutrients.

A small blunder on your part can result in stunted plant growth, or in some cases, it can kill the whole plant.

  • Mushroom compost is alkaline, so you must recheck the optimal pH of your growing vegetable plants.
  • Avoid direct contact of seeds with mushroom compost. Research states that mushroom compost reduces the germination process.
  • Most commercially grown mushrooms use chemical-incorporated pesticides, so organic gardeners should check for certified organic mushroom compost. Otherwise, you may add chemical residues to your organic veggie garden.
  • The best time to use SMC for vegetable plants is during early spring. It allows the organic compounds to decompose efficiently and release required nutrients into the soil.
  • As mushroom compost locks moisture for longer, you should ensure proper drainage to avoid overwatering.
  • Limit the use of mushroom compost, as excess use can impact plant’s ability to absorb nutrients.
  • After applying SMC, monitor your plant for any signs of nutritional imbalance.
  • Use only fully decomposed mushroom compost.

Mushroom Compost Alternative for Vegetable Garden

As most commercially grown mushroom farms use chemical pesticides, organic gardeners won’t prefer the by-products of such farms.

Alternatively, you’ve plenty of other options to enrich your vegetable plants.

  • Well-rotted manure: Rich in primary nutrients that every vegetable plant needs to thrive. It also improves soil texture, drainage ability, and water retention of growing mediums.
  • Bone meal: It is a slow-releasing fertilizer rich in phosphorus and potassium. 
  • Worm castings:¬†Vermicasting is regarded as black gold; it is one of the effective ways to convert your kitchen scrap into nutrient-rich fertilizer.
  • Fish Emulsion: This liquid fertilizer is a by-product of fish and has readily available nutrients.
  • Compost: The nutritional ability of old compost can’t be ignored. It includes various degradable materials that add organic matter to your garden.
  • Leaf Mold: Decomposed leaves are rich in humus, which promotes plant growth and increases the soil’s water-holding capacity.
  • Alfalfa Meal: Rich in nitrogen, it is derived from the alfalfa plant.


Mushroom compost is a by-product of mushroom farming. It includes different materials that are organic and also have some nutritional benefits.

It is regarded as one of the best soil amendments, including organic compounds to the growing medium.

Like most natural fertilizers, SMC releases nutrients slowly. So you don’t have to worry about over-fertilization.

However, the substrate is rich in soluble salts that can negatively impact the optimal growth of vegetable plants.

Also, mushroom compost is alkaline. So, acid-loving vegetable plants may not like the excess use of this compost.

Though few things must be taken care of, your vegetable garden can benefit from mushroom compost.

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