Why Does Your Soil Smell Like Ammonia? How to Fix Smelly Soil

Co-authored by Lindsey Swett and Amber Crain

Last Updated: April 30, 2024 Fact Checked

If you've noticed a sharp, ammonia-like odor coming from your soil, you're probably wondering what could possibly cause such a thing. Don't worry—this is a common gardening issue and it's something you can fix on your own! In this article, we'll be answering your most common questions about soil that doesn't smell quite right. We'll also explain how to get rid of that funky odor and improve the health of your soil.

Question 1 of 6:

What causes soil to smell like ammonia?

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1
Soil with poor drainage often develops an ammonia smell. If soil doesn't drain well, it can quickly become saturated with water. Saturated soil is often dark in color and the perfect breeding ground for anaerobic bacteria, and this often leads to a funky ammonia smell, particularly if the soil contains excess urea. ^{[1]
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- To test the drainage in your garden, dig a 12x12x12 in (30x30x30 cm) hole and fill it with water. If the water drains completely in 3 hours or less, your soil has good drainage and the ammonia smell is likely being caused by something else.
Soil with decent drainage can still become waterlogged and stinky if too much water is introduced. If your soil never gets a chance to dry out, it can develop an ammonia-like odor. ^{[2]
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A lack of oxygen can make your soil smell like ammonia. Soil that lacks a healthy amount of oxygen is called “anaerobic” soil. A lack of oxygen can cause several problems, all of which can contribute to soil odor. ^{[3]
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Research source} Anaerobic soil usually has one (or all) of the following characteristics:
- Heavy, sticky, or gray in color, indicating a large amount of clay is present
- Hard, dense, and difficult to turn or till, indicating soil compaction
- Waterlogged and consistently wet, indicating poor soil drainage ^{[4]
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Question 2 of 6:

How do I fix soil that smells like ammonia?

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Add organic amendments to improve drainage or aerate compacted soil. Fibrous organic amendments like peat, wood chips, tree bark, and straw are most effective for soils that are heavy, dense, or waterlogged. ^{[5]
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Research source} Start by spreading a 2–3 in (5.1–7.6 cm) layer of your chosen amendment over the soil’s surface. Then, mix it into the soil using a tiller, shovel, or digging fork. Ideally, amend your soil 3-6 weeks before you start planting. ^{[6]
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- Be sure to incorporate organic matter evenly throughout the garden.
- Avoid working amendments into wet soil since this can make compaction worse. ^{[7]
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Water less often if drainage is fine and the soil isn't compacted. If the soil itself is fine, back off on how often you water it. In general, aim to provide 4 in (10 cm) of water every 8 days. ^{[8]
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Research source} If you have plants growing in the soil already, their roots will soak up water faster, so you may need to water more often. It helps to experiment by doing things like:
- Digging a 12x12x12 in (30x30x30 cm) hole before watering. If the soil is visibly wet, hold off on watering for a few days.
- Filling the hole with water to check the drainage. If the water isn't absorbed in 3 hours or less, it's waterlogged. Don't water your soil yet.
- Using a rain gauge in wet climates. Just stick the gauge into the soil and check the reading periodically to figure out when you need to add more water to the soil. ^{[9]
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Question 3 of 6:

What does healthy soil smell like?

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Good soil usually smells neutral, but it may also smell pleasantly earthy or even slightly sweet, especially right after you till it. If your soil smells sour, rotten, or has an odor similar to ammonia, your soil isn’t healthy. In most cases, the problem is inadequate drainage or soil compaction.

Question 4 of 6:

Why does my potted plant smell like ammonia?

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Potted plants may smell like ammonia if you're watering them too often. Waterlogged soil is a breeding ground for anaerobic bacteria which is a leading cause of soil odor. Performing a simple touch test every day can help you avoid overwatering container plants. ^{[10]
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- To do this, stick your finger into the top 1 in (2.5 cm) of soil. If the soil feels damp, don't water your plant yet. Wait until the soil feels dry to the touch before watering again.
Check the bottom of each potted plant to make sure there are drainage holes. If the pot doesn’t have any drainage holes, or if the holes are really small, water isn’t able to drain through properly. This leads to foul odors and can cause diseases like root rot. ^{[11]
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Avoid using regular garden soil or other dense soil mixes for your container plants. Lightweight potting mixes work best for potted plants because they stay loose (so they don’t get compacted over time) and they drain well (which prevents oversaturation). ^{[12]
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Question 5 of 6:

How do I fix a smelly potted plant?

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Look for a soilless potting mix made of peat moss, vermiculite, and/or perlite. Soilless potting mixes are lightweight, porous, and perfect for growing container plants. ^{[13]
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Research source} You can even make your own soilless mix by combining equal parts peat moss and vermiculite (or perlite). ^{[14]
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Use a pot with more drainage holes. Choose a container that has drainage holes on the bottom or sides. If the drainage holes are on the bottom of the container, remember to position your potted plant so it’s slightly elevated off the ground to allow for proper drainage. If the container must sit directly on the ground (or any other flat surface like a table or shelf), it needs to have drainage holes on the sides (rather than the bottom). ^{[15]
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- If you don’t want to repot your plants, you can also drill extra drainage holes into the bottom or sides of the container.

Question 6 of 6:

Why does my compost smell like ammonia?

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Green materials (like grass clippings) are high in nitrogen, and too much nitrogen causes an ammonia-like odor. To fix this, turn your compost with a garden shovel and spread out the pile a bit so the excess nitrogen can evaporate. Then, mix in more brown material (brown leaves, mulch, etc.) to restore the balance.

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Why Does Your Soil Smell Like Ammonia? How to Fix Smelly Soil

Steps

What causes soil to smell like ammonia?

How do I fix soil that smells like ammonia?

What does healthy soil smell like?

Why does my potted plant smell like ammonia?

How do I fix a smelly potted plant?

Why does my compost smell like ammonia?

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