6 Common Reasons Why Your Topsoil Stinks

Topsoil should smell fresh and earthy, not sour, fishy, or moldy. Bad-smelling topsoil should be treated as quickly as possible to preserve the plants and prevent root rot. The good news is there are only a handful of explanations for foul odors coming from the topsoil.

Your topsoil stinks for these reasons:

• Bad soil drainage
• Bacterial growth
• Bad manure in the topsoil
• Expired topsoil
• Foul organic matter
• Not enough oxygen in the topsoil

Throughout this article, you’ll find out why your topsoil smells bad, what you can do about it, and how to prevent it from smelling bad in the coming months and years. If your topsoil has a bad odor, it’s time to take action.

Poor Soil Drainage

Science Friday claims poor drainage is the primary reason topsoil develops a gross smell. This happens because the damp soil invites fungus. The fungi in the soil give off a foul odor as the spores spread throughout the lawn. Fungi on the lawn look white, dusty, and sometimes develop as mushrooms.

How to Fix

You can fix poor topsoil drainage with these steps:

1. Aerate the soil.
2. Add peat moss to improve the drainage and limit excessive water retention.
3. Till compact dirt before adding the topsoil.
4. Consider additional additives, such as compost and dehydrated manure.

Miracle-Gro Sphagnum Peat Moss is an excellent choice because a little goes a long way. This peat moss improves water drainage without rebounding too much moisture. You can use it with topsoil, native soil on the ground, or potting mix.

Check out this helpful YouTube video for more topsoil drainage tips:

Bacteria and Mold on the Topsoil

Bacteria and mold create gross odors that drench the topsoil. They’re one of the many reasons your lawn smells bad. The mold smells musty, almost like a damp, mold-filled closet. On the other hand, the bacteria can range from a sour odor to a pungent fishy scent.

How to Fix

Scotts DiseaseEx Lawn Fungicide is one of the top products I talk about on this website. It has more than enough treatment for several thousands of square feet, not to mention the fact that it targets more than 20 diseases and fungi in the soil. You can use it to rid the topsoil of those gross odors and dangerous contaminants.

Bad Manure in the Compost

According to Crate and Basket, hydrated manure can ruin the topsoil. Many topsoils and compost bins contain manure for its nitrogen-rich composition. This manure should be dehydrated to remove the bacteria and prevent them from growing back.

How to Fix

For starters, it’s important to get rid of saturated manure. Any manure used in your yard should be dehydrated; otherwise, it will encourage bacteria, mold, mildew, and disease. Adding too much manure to the mulch will make it smell gross, too.

Always inspect the topsoil you intend to use on your lawn or in the garden to ensure the manure is dehydrated. You could also steer clear of manure if your yard gets a lot of rain. The rain can hydrate the manure quickly, leading to strong odors.

Expired Topsoil

Topsoil usually only lasts for a few years. Some bags are labeled with maximum effectiveness of six months. Make sure you check the expiration date before storing the topsoil. Most of these bags contain moisture and organic matter than can develop bacteria. Spreading expired topsoil will inevitably change the smell of the yard.

How to Fix

Keep these tips in mind when handling expired topsoil:

• Never use topsoil that’s more than a couple of months beyond its expiration date.
• Store your topsoil and grass seeds in sealed, airtight bags.
• Throw away any topsoil that’s soaked and in a bag unless you intend to use it (the moisture can lead to bacterial growth).
• Check the ingredients to know how quickly the topsoil will expire after using it.
• Always look for the expiration date before getting a new bag of topsoil (some companies put the oldest topsoil near the front to encourage people to get it off the shelves).
• Don’t mix store-bought topsoil with anything else unless the company tells you that you can.

Stinky Organic Matter

If you make your own topsoil or compost, it’s time to take a look at what’s inside. Boxwood bushes smell bad, as do Bradford pear trees and many other plants. Everything you put into the topsoil or compost will alter the odor, including rotten food, manure, and any pests that leave droppings in the mixture.

How to Fix

Follow this five-step process to get rid of stinky organic matter that makes your topsoil smell bad:

1. Smell all of the plants and clippings you intend to use in the topsoil.
2. Remove as many weeds from the topsoil as possible (note that all topsoil will likely have small weeds in them).
3. Don’t use topsoil that has fungi, mold, mildew, or oily plant clippings.
4. Remove the top layer of topsoil from the lawn or garden, then add a new layer that smells earthy and fresh.
5. Get rid of pet and pest feces from the topsoil as quickly as possible to keep flies and stinky odors away.

Lack of Oxygen in the Topsoil

If there’s not enough oxygen in the topsoil, your yard will grow anaerobic bacteria. Anaerobic bacteria can doesn’t require oxygen, so it thrives in saturated, compact topsoil. It makes your yard smell fishy and can lead to root rot and other root issues.

How to Fix

The best way to improve the oxygen levels in topsoil is to aerate the soil. Use aeration boot attachments, shovels, and other tools to sift the topsoil. Never let the topsoil get compacted or it’ll prevent the grass and other plants from getting enough oxygen. This process leads to root rot and deterioration.

The aforementioned peat moss mixture is another solution to improve the oxygen in the topsoil. Peat moss prevents water from pooling on top of the dirt. It absorbs and distributes water, encouraging healthy oxygen levels, hydration, and nutrient absorption.