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The Truth About Potting Soil and Mask Requirements

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There’s been an unprecedented increase in the use of face masks since early 2020. It’s become common to see people wearing face masks; for some, seeing crowds of people together without this new dress code triggers panic. We have become acutely aware of airborne pathogens. When working with compost or potting soil, is wearing a facemask a sign of the times, or is it advisable?

The USDA does not regulate potting soil production in the United States. Aspergillus fumigatus and Legionella are fungi found in composts and potting soils and cause severe pulmonary infections, including Legionnaires disease. Wearing a mask is advisory.

Table of Contents

Fear not, oh, feeble and fainthearted one. The actual recorded cases of gardeners and potting soil manufacturers becoming ill from working with their products are sporadic – no pun intended. But is it worth taking precautions? Let’s look to make an informed decision, shall we? Read on.

Picture of cupped hands holding potting soil
Compost Work in Progress


The U.S. Composting Council defines compost as a product manufactured through the controlled aerobic, biological decomposition of biodegradable materials. The product has undergone mesophilic and thermophilic temperatures, which significantly reduces the viability of pathogens and weed seeds (by EPA 40 CFR 503 standards) and stabilizes the carbon such that it is beneficial to plant growth. Compost is typically used as a soil amendment but may also contribute plant nutrients. (AAPFCO definition, official 2018)  Finished compost is typically screened to reduce its particle size, to improve soil incorporation.

The USCC certifies compost manufacturing, but their only tests for pathogens are for Fecal Coliform or Salmonella – California is the only state that requires a pass on both. They also require manufacturers to meet the EPA limits for heavy metals.

Why Not Make Your Compost?

Adding compost—nature’s fertilizer—is one of the best ways to augment the soil in your garden. Also, you can easily make it and cut back on the yard and kitchen waste. Compost is simply a product of nature’s recycling program.

Composting speeds the decomposition process up, starting with bacteria, fungi, protozoa, and larger organisms such as earthworms and beetles. The whole process will render available nutrient soil able to break heavy clay and improve the capacity of sandy soil to hold nutrients and water.

What You Need to Get Started

First, decide where you want to compost. Remember that the process is continuous, with ongoing input and a constant supply of compost, so consider the location carefully. Choose a place with some sun, good drainage, and level. Ground that has been turned and is a ready source of worms is ideal.

Any materials you compost will have both carbon and nitrogen in their tissues. Carbon is an energy source for microorganisms decomposing, and nitrogen provides the organisms’ proteins to grow. A rule of thumb is that materials with a carbon-to-nitrogen ratio (C: N) of 30:1 offer a suitable environment for compost microorganisms; a 30:1 ratio will give you a hot, quick-acting compost pile.

Materials used for composting are commonly divided into two categories to make managing a compost pile easier: brown and green.

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Brown materials

Brown materials are relatively high in carbon. Here are some common examples of brown materials to add to your compost bin.

Sawdust and wood chips.

But since the wood takes a long time to break down, it should be used in very shallow layers or mixed with green materials.  Avoid chemically treated timber with a greenish hue.

Wood ash.

Use only small amounts of wood ash has high levels of alkaline that can inhibit the microbes doing the work in the compost pile.

Dead leaves.

Shred them to speed up the process. Also, layer them, so they don’t choke the mix, cutting off aeration. Avoid waxy leaves and black walnut leaves as they contain juglone, a material that inhibits the growing ability of many plants.


High in carbon and nitrogen creates air passages to get microbes in the compost.


It breaks down well and helps clay soils better absorb water and nutrients. High in carbon but lower nitrogen levels.

Paper and cardboard.

Shred paper and cardboard. Avoid color-printed, glossy magazines or posters. You may choose to dampen lightly before adding to your compost.


Teabags are a good addition.


A good source of calcium. Crush them to speed up the decomposition rate. DO NOT use whole eggs or parts other than the shell.

Green Materials

Green materials have a relatively high amount of nitrogen. Here are a few commonly used green composting materials:

Vegetable and fruit peelings.

Your compost pile is a vegetarian; don’t feed it oil, cheese, or moldy bread.

Grass clippings.

High in nitrogen and commonly available. If you are using long-lasting commercial weed killers, DO NOT add them to the compost heap; instead, leave them on the lawn. Also, spread it in layers between brown material in the compost bin.

Coffee grounds.

There is a love triangle between compost, coffee grounds, and worms. The latter loves coffee, but compost loves worms – so they all lived happily together.

Fresh manure.

High in nitrogen and is an excellent green composting material. Avoid waste from pets, pigs, and people. Use manure from cattle, horses, chickens, sheep, goats, and rabbits.

Plant clippings.

Don’t use any diseased plants. Cut branches down to smaller sizes – about an inch.

The Process

Good weather for growing plants means good weather for composting. But because composting generates heat, the composting season is often extended beyond the growing season.

Composting is a simple process; combining nitrogen and carbon in the materials, you use this to create an optimal environment for the work of the microbes and other organisms. Adding a little effort to the process can significantly shorten the time.

Converting to work, the size of your container needs to be three-foot by three-foot. These dimensions are essential, so stick to them. A larger container will prevent oxygen from getting to the pile’s center. A smaller container will not allow enough microbes to do their work.

Placing some woody materials directly on the upturned earth (for worms) will allow oxygen to get to the compost. Combine nitrogen-rich green materials with an equal amount of carbon-rich brown materials in two to four inches deep layers. The effort part of the equation is that you make sure that air remains available throughout the pile. You can do this by switching between bins.

Below is a table with common green and brown materials and their nitrogen content ratios.

Coffee grounds 20:1Sawdust 50:1Pine needles 70:1
Corn stalks 60:1Straw 40:1 to 100:1Poultry manure 10:1
Cow manure 20:1Hay from legumes 15:1Seaweed 19:1
Eggshells 12:1 to 15:1Horse manure 25:1Vegetable wastes 12:1 to 20:1
Fresh grass clippings 15:1Leaves 40:1 to 60:1Wood chips 100:1 to 500:1
Fruit wastes 25:1 to 40:1Paper 170:1
Nitrogen Ratios

Potting Soil

Growing strong, vigorous plants that will thrive requires a suitable potting mix. Because of the risks of uncertified potting soils, it may be an option to consider National Organics Standard-certified products. At least that way, you can be confident that your potting soil conforms to a healthy standard.   

The chemical, physical, and biological qualities of a perfect organic potting mix include the following. Pore space will be present to allow for air and water retention and the rapid growth of roots throughout the media. It will be chemically balanced, with the appropriate pH and nutrients for plant growth – or the ability to retain nutrients provided later in liquid fertilizer.

It will also be biologically active, including the microorganisms required to mineralize organic fertilizers, control plant diseases, and maintain plant health. You can view commercially available organic potting mixes at the Organic Materials Review Institute (OMRI) website.

Making Your Potting Mix

Making your potting mix is relatively straightforward and can save you money, but it does involve an investment of time and some planning ahead. Also, you will need a location on your property where you can store and mix bulk ingredients.

The Basic Recipe

The best recipe for you depends on the ingredients you can access and the intended purpose of the potting mix. Substituting Coconut coir for the peat moss vermiculite mix is a good option.

An ideal potting mix contains nitrate-nitrogen at 10 to 200 ppm, phosphorus above three ppm, potassium above 25 ppm, calcium above 30 ppm, magnesium above ten ppm, and sodium and chloride below 130 and 200 ppm, respectively.

Using a recipe containing a complete fertilizer blend and testing the performance in small batches, you can assess the supply of nutrients without measuring nutrient concentration. Below is a recipe from ATTRA:

Organic Fertilizer Blends for Potting Mix

Eliot Coleman Base Fertilizer Mix (published in The New Organic Grower, 1995)

Add 3 cups of fertilizer mix for every 20 gallons of coconut coir

  • 1 part blood meal
  • 1 part colloidal (rock) phosphate
  • 1 part greensand (glauconite)

Other FAQs for Composting


Whether creating your compost or mixing your potting soil, protecting your health is vital. This isn’t a CDC or WHO warning; it’s merely an encouragement to protect yourself adequately when working with either compost or potting soil. Wearing a face mask is prudent.

Compost can harbor deadly microorganisms, some of which have killed or severely injured unwary gardeners. Below is a synopsis of the potential risks:

  • Aspergillosis is a fungus that causes a pulmonary illness after inhaling a fungus typically found in rotting plant debris. While aspergillosis is usually not life-threatening, it can be deadly if you inhale enough spores.
  • Farmer’s Lung has symptoms similar to pneumonia and can be caused by inhaling specific fungal and bacterial pathogens found in rotting organic materials, including mushrooms, hay, and sugar cane.
  • A fungus found in guano and bird droppings causes histoplasmosis. Healthy immune systems can typically fight off histoplasmosis.
  • The inhalation of L. Longbeachae causes Legionnaire’s Disease, a respiratory infection.
  • A local infection that affects the tissue around the fingernails and toenails is known as paronychia. Long-term dampness and the abrasive impacts of dirt can cause skin holes, spread infection, and cause discomfort and throbbing.
  • Tetanus is a central nervous system disorder caused by bacteria commonly found in soil.

We do not wish to scare you, merely to inform you.  The above cases are rare, but as we all know – prevention is cheaper than the cost of cures. Would you please look after yourselves and wear protection where it is sensible to do so?

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