Why does my garden smell like ammonia?

If you've noticed a pungent ammonia-like scent coming from your garden's soil, you're probably wondering what's causing it. Don't worry—this is a common issue in gardening, and it's something you can easily fix yourself! In this article, we'll answer the most frequently asked questions about strange odors in the soil. We'll also share tips on how to eliminate the unpleasant smell and improve soil quality.

Poorly-draining soil often traps ammonia odors. If your soil isn't draining properly, it can quickly become waterlogged. Waterlogged soil creates an ideal environment for anaerobic bacteria to thrive, which typically results in an ammonia-like smell.

• To check your garden's drainage, dig a 30x30x30 cm hole and fill it with water. If the water is absorbed within 3 hours, your soil has good drainage, and the ammonia smell may be due to other factors.

Overwatering or excessive rainfall can lead to an ammonia-like smell in the soil. Even soil with moderate drainage can become waterlogged and develop an odor if too much water is poured in. If the soil has no chance to dry out, it will gradually begin to smell like ammonia.

Lack of oxygen in the soil can also produce an ammonia-like odor. Soil without enough oxygen is called 'anaerobic.' Oxygen deficiency can lead to several issues, all of which contribute to the unpleasant smell in the soil. Anaerobic soil often exhibits one or more of the following characteristics:

• Heavy, clay-like, or gray-colored, indicating a high clay content
• Hard, compacted, and difficult to till, indicating soil compaction
• Waterlogged and always wet, indicating poor drainage

Add organic soil amendments to improve drainage or till compacted soil. Organic soil amendments like peat moss, sawdust, bark, and straw are most effective for heavy, compacted, or waterlogged soils. Start by spreading a 5-8 cm layer of your chosen soil amendment across the surface. Next, use a tiller, shovel, or garden fork to mix it into the soil. It's best to amend the soil 3-6 weeks before planting.

• Make sure to evenly mix the organic matter throughout the garden.
• Avoid mixing soil amendments into wet soil, as this will further compact the soil.

Reduce watering frequency if the soil drains relatively well and is not compacted. If the soil drains well, you should reduce the frequency of watering. Generally, water about 10 cm every 8 days. If you have plants in the soil, their roots will absorb water more quickly, so you'll need to water more often. Try these methods:

• Dig a 30x30x30 cm hole before watering. If the soil is noticeably wet, skip watering for a few days.
• Pour water into the hole to test drainage. If the water is not absorbed within 3 hours, your soil is waterlogged. In this case, skip watering.
• Use a rain gauge in wet climates. Simply insert the rain gauge into the soil and check the readings periodically to know if additional watering is necessary.

Healthy, clean soil generally has little to no odor. Good soil often has no distinct smell but may have a pleasant, earthy scent, or even a slightly sweet aroma, especially after being tilled. Soil that smells sour, rotten, or like ammonia is unhealthy. In most cases, this is due to poor drainage or compacted soil.

Potted plants may develop an ammonia-like smell if they are overwatered. Waterlogged soil is an ideal environment for anaerobic bacteria to grow, which causes the unpleasant odor. A simple test by touching the soil can help prevent overwatering your potted plants.

• To perform the test, simply insert your finger about 2.5 cm into the soil. If the soil still feels moist, wait before watering. Only water when the soil feels dry to the touch.

Pots with poor drainage can lead to ammonia odors. Check the bottom of your plant pot for drainage holes. If the pot lacks drainage holes or if the holes are too small, water won't drain properly. This can cause a foul smell and may lead to plant diseases like root rot.

Compact soil can cause ammonia-like odors in potted plants. You should avoid using garden soil or other compact soil mixes for potted plants. Lightweight soil mixes are best for container plants as they maintain their fluffiness (not compacting over time) and drain well (helping to prevent waterlogging).

Repot your plants with a light, well-draining potting mix. Look for a potting mix that doesn't contain garden soil but is made from peat moss, vermiculite, and/or perlite. These soilless potting mixes are light, airy, and perfect for potted plants. You can even create your own mix by combining equal parts of peat moss and vermiculite (or perlite).

Use pots with more drainage holes. Choose plant pots with drainage holes at the bottom or on the sides. If the drainage holes are at the bottom, raise the pot slightly to allow water to drain more easily. If your pot must sit directly on the ground (or flat surfaces like tables or shelves), make sure it has drainage holes on the sides instead of just at the bottom.

• If you don’t want to repot your plant, you can drill additional drainage holes at the bottom or sides of the pot.

Your compost might contain too much green material rich in nitrogen. Green materials (such as freshly cut grass) are high in nitrogen, and an excess of nitrogen can cause an ammonia-like odor. To address this issue, use a shovel to turn the compost and spread it out a bit to allow the excess nitrogen to evaporate. Then, mix in some brown materials (such as decayed leaves or mulch) to restore the balance in your compost pile.