Why Does Mulch Smell Like Poop?

The benefits of mulch to your lawn range from providing aesthetics to enhancing water /airflow. Despite their importance, mulches sometimes produce odd smells. So, why does mulch smell like poop?

Mulch sometimes smells like poop due to anaerobic decomposition. Anaerobic decomposition mostly happens if the mulch layer is too thick, preventing the entry of oxygen. As the thick mulch layer decomposes, it generates hydrogen sulfide and methane gasses, which smell like poop.

Mulch will undoubtedly generate odd odors as it decomposes in your lawn/garden. Read on and learn the sources of these odors and how to get rid of them.

Why Does Mulch in My Garden Smell Like Poop?

Mulch produces highly unpleasant poop-like odors if it decomposes anaerobically. Bacteria and fungi facilitate this decomposition, producing hydrogen sulfide gas, methane, and acetic acid, which has an odor similar to ammonia.

Anaerobic decomposition happens when mulch is too wet and dense to enable sufficient oxygen to flow through. Mulch decomposes over time because it consists of living organisms. This decomposition is entirely normal and does not produce excessive foul smells if it occurs under the right conditions and with ample oxygen.

While mulch decomposition may produce unpleasant odors, they should not be very overwhelming. Mulch smelling like manure is particularly prevalent with commercial mulch. Sometimes even freshly acquired mulch already has a foul odor.

When mulch is produced commercially, it is sometimes stacked high. The mounds compress the mulch, leaving little space for air. After that, the mulch is stored in sealed bags, further restricting the mulch’s air access. This issue can also happen with homemade mulch if it is piled too tightly or spread out in anaerobic conditions.

Poop-smelling gasses from decomposing mulch can be detrimental to plants on your lawn. These gasses might cause plants to wilt or change the color of leaves to brown/yellow.

To ensure that your mulch does not smell bad, ensure that the mulch is applied at a maximum depth of 3 inches. This will allow the mulch to decompose with access to oxygen, preventing odors and allowing water and various microorganisms to break it down.

What Smell Should Mulch Possess?

Mulch should have an earthy, natural scent similar to rich soil. Despite being faint, the smell of mulch significantly overwhelms the nearby smells of soil and grass but is overpowered by flowers and other fragrant plants. The distinct smell of mulch depends on the materials that make it.

If your mulch smells like manure, consider getting to the root cause of the problem because this mulch could be detrimental to your plants. Understanding why does mulch smell like poop gives you a better idea of what you are dealing with. In return, you will be able to find a long-term solution and not quick fixes.

How to Remove Poop Smell From Mulch

Mulch smelling like poop shouldn’t be of much concern since the smell often fades away with time. However, if the smell of poop in your mulch is too strong, you may do a few things to reduce it.

Spread a Layer of Soil on the Mulch

Spreading soil helps bury the decomposing mulch, reducing the amount of poop-smelling gas. Adding a layer of soil to your mulch also comes with additional advantages, including:

  • Reducing weed growth and facilitating their eradication
  • Reducing evaporation
  • It gives garden beds a complete, polished look

Sprinkle Baking Soda, Lime, or Coffee Grounds

Baking soda and lime help mask the manure smell, while coffee grounds help absorb the foul smell from the mulch. Ensure you are generous with these products to achieve the best results.

Spread the Mulch on Open Space 

Secure an area in your lawn or garden where you can spread your mulch. Water the mulch and flip it frequently. Once the mulch is laid out and watered, the gasses will be released, and anaerobic decomposition will cease.

Flip or Turn the Mulch Often

Often flip the mulch to enhance air circulation and aeration. Oxygen deprivation promotes the growth of anaerobic bacteria, which thrive without oxygen. These bacteria perish when the pile is stirred frequently.

Add Dry Leaves to Your Mulch

Adding dry leaves to your mulch helps avoid compaction, retain water, and insulate the soil from extreme temperature swings. 

Wait Until the Weather Is Warmer

Applying mulch to your garden during the warmer seasons is better than when the temperatures are cold. Higher temperatures will diminish the odor’s perceptibility.

Don’t Stockpile Mulch for Future Use

Avoid letting the mulch pile up before use or sitting stationary for too long. If you are stockpiling mulch for future use, you must thoroughly mix it using an aerator. If you let it sit for too long, you will be left with a pile of decomposing mulch.

Consider Utilizing Gravel or Landscaping Rocks

Rocks and gravel don’t decompose and won’t release foul smells. Gravel keeps the soil moist, discourages weeds, and gives planting beds a polished finish. Compared to bare soil, gravel mulch may retain soil moisture more effectively.

Utilize Cedar Chips To Minimize Manure Odor

Covering the mulch with cedar chips aids in odor absorption. The smell of cedar overpowers the smell of manure and makes the environment more bearable.

Wait some time after implementing the modifications before judging whether the mulch still smells like poop. It takes a few days to see a difference, but the foul odor will gradually disappear.

Even though timelines are subject to change, it should not take longer than a week. If your mulch continues to emit a foul odor after a few weeks, you may need to discard it and find alternative mulches to use.

Final Thoughts

So, why does mulch smell like poop? Your mulch smells like poop because it’s undergoing anaerobic decomposition, releasing hydrogen sulfide and methane gasses. Avoid unpleasant odors by ensuring your mulch isn’t over 3 inches thick.

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