Is Horse Manure Good For Clay Soil? (Everything You Need To Know)

  • Date: April 20, 2022
  • Time to read: 4 min.

I​f you’re trying to grow plants, having the right soil conditions is key. Clay soil presents challenging issues for gardeners–it’s tightly-packed, meaning water and air struggle to infiltrate the soil. This can make it difficult to grow much of anything, but amending the soil can help. Is horse manure good for improving clay soil?


H​orse manure is good for clay soil. It helps to improve the drainage and aeration of the soil, providing habitat for earth worms and beneficial bacteria to thrive. Over time, the composition of the soil improves and allows for higher yields.

I​n the rest of this article, we’ll dive deep into what makes horse manure a good addition to clay soils and discuss possible drawbacks to adding it to your garden.

W​hat Is Horse Manure?

O​f course, horse manure is mainly horse waste. However, horse manure is more complex than just the road apples horses leave in their stalls. It’s also made up of other organic substances, like shavings, straw, or spilled grain.

T​hese other organic substances are important when discussing clay soils because they give horse manure the ability to not only fertilize soil, but also change its structure. Broken down pieces of shavings and straw create pockets in the soil for moisture and air to settle.

W​hen moisture and oxygen levels in soil increase, so do earthworm numbers. As the worms crawl through the soil, they leave nutrient-packed waste that will feed plants for years to come. By tunneling through the soil, they also continue to improve the water drainage and oxygen levels.

As the manure is removed from the horse’s stall, it’s typically placed into a compost bin and left to break down over time. This waiting period is important because fresh horse manure is typically alkaline and may occasionally burn plant leaves if applied too soon. After composting, the manure will be fairly neutral and ready to improve the soil.

H​ow Long Does Horse Manure Need To Compost?

B​efore you decide to use horse manure on your clay soils, make sure to leave it alone long enough for it to become neutralized. According to the Colorado State University Extension, your manure should sit out for at least four months before planting anything in it (especially vegetables).

I​f you compost your manure with other organic materials, the wait time may be reduced. This is due to the high levels of heat reached inside of properly-managed compost piles. This heat will speed up the process of breaking down the materials in the manure and kill any weed seeds.

A​s a general rule, you should wait three to four months before placing horse manure on your clay soils. Even if it’s not completely composted, it will be safe to use on your yard or garden. It will continue to break down as nutrients are leached into the soil below.

Drawbacks Of Using Horse Manure On Clay Soils

W​hile using horse manure on clay soils is a great way to improve the composition of the soil, there are a few drawbacks. Most of these can be avoided by properly handling your horse manure and waiting an appropriate amount of time before applying it to the soil.

  • I​t’s high in nitrogen. This is especially true when the manure is fresh. While many plants appreciate a nitrogen boost, too much all at once can be detrimental. By letting the manure age for a few months (or even a year), the nitrogen levels will decrease.
  • I​t’s alkaline when fresh. While this is helpful for neutralizing acidic soil, it can thwart the growth of acid-loving plants like blueberries. After composting, horse manure is neutralized, making it a great addition to all soils.
  • I​t smells, well, horsey. Horse manure smells significantly less than many other types of manure (hello, cow manure!), but it still has a unique scent. You can reduce this smell by composting it with leaves, food scraps, and other compost materials for several months.
  • I​t can have weed seeds in it. Horses who graze, and even those who eat strictly commercially-grown hay, will consume some weed seeds. It’s obviously not ideal to sprout weeds in your garden, so let the manure compost in a hot compost pile before using it. The high heat levels will kill any weed seeds present in the manure.

F​inal Thoughts

T​he combination of waste and organic matter in horse manure makes it a wonderful choice to add to clay soils. Though it needs time to cure before being used, it improves water drainage and provides habitat for beneficial organisms. When treated with properly-cured horse manure on a yearly basis, the composition and fertility of clay soil will increase substantially.

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