Horticulture Magazine

Using Horse Manure Compost In The Garden

fresh horse manure

Using horse manure in your garden can help maintain fertility – but it is best used only after it is thoroughly composted.

In this article, we will explore this mucky issue in a little more depth, including why you might wish to use horse manure compost in your garden.

We will delve into the properties of this useful organic material and explore where you might source horse manure if you do not keep horses yourself.

And whether or not you do keep horses yourself, we will run through how to compost horse manure so you can use it, and how and where to use it once you have.

Read on to get one step closer to using horse manure to create a healthy organic garden.

Why Use Horse Manure Compost?

a Welsh pony stood in long grass

Like other manures, and other home compost, horse manure compost is an organic material that can help you take care of the soil in your garden and provide the plants you grow with the nutrients they need.

Horse manure will improve the nutrient content of the soil, and improve its structure.

It will help ameliorate drainage and compaction issues with heavy clay soils.

Using horse manure compost in your garden will also improve the soil’s ability to retain moisture and can be especially useful to improve free-draining soils too.

What is more, using organic material like horse manure can help you sequester carbon in the soil in your garden – so you will be doing your part in combatting our climate crisis.

Horse Manure Properties

gloved hands holding horse manure

If you are using manure in your garden, it is important to understand that different manures have different nutrient profiles and characteristics.

They have different levels of NPK (nitrogen, phosphorus and potassium) – the three key plant nutrients.

Horse manure typically contains around the same amount of nitrogen as sheep manure.

It typically has a little less nitrogen than rabbit manure and chicken manure, but a little more than cattle manure and more than a typical homemade compost.

It does not contain as much phosphorus as other manures but does usually have more than material from your compost heap or bin.

illustration showing the benefits of nitrogen, phosphorus and potassium

In terms of potassium, horse manure will typically compare favourably to other manures, though sheep manure will typically have a little more.

The nutrient profile of horse manures can vary significantly, depending on the source, what horses are fed etc.

However, NPK values for horse manure can typically be around 0.5% nitrogen, 0.3%  phosphorus and 0.4% potassium – to give a general idea. [source]

Many gardeners consider horse manure to be the finest manure to use in a garden, especially fine when combined with straw bedding to create compost.

However, it is worth noting that one downside to horse manure is that it does tend to be full of seeds.

Which can increase the amount of weeding you have to do if it is not first composted correctly.

Sourcing Horse Manure

horse manure with horses eating in the background

If you have your own horses, then of course you will already have horse manure on hand.

If you do not, you might wonder where you can get your hands on some for your garden.

You will usually be able to source horse manure compost from a reputable supplier online.

You may also be able to make an arrangement to collect either composted horse manure or horse manure that you can compost yourself at home if you reach out to local equestrian centres, riding schools, stables, farms, or rural horse owners in your area.

However, when sourcing horse manure, it is important to make sure that the horses were reared sustainably, and that the horse manure does not contain substances that may pose a risk to your health, or to the environment.

This is especially important, of course, if you are growing food in your garden.

Why It Must Be Composted Before Use

a fresh pile of horse manure with fencing in the background

Horse manure must be composted before use for a range of reasons.

The first reason is that fresh manure of most types can bring pathogenic risks to you and other members of your household. [source]

Fresh manure can harbour bacteria which can be dangerous. [source]

The second reason is that fresh manure is usually too ‘hot’ to use directly around your plants.

hand trowel scooping manure

It is very high in nitrogen and while all plants need nitrogen (along with phosphorus, potassium and a range of micro-nutrients) to grow, too much nitrogen can scorch or even kill your plants. [source / source]

The only manure that can usually be used directly in the garden is rabbit manure. [source]

One additional reason to compost horse manure before use is that, as mentioned above, horse manure is typically full of weed seeds, which can germinate and cause excessive weed growth in your garden.

Composting at sufficiently high temperatures can kill seeds and prevent this problem from occurring.

How To Compost Horse Manure

horse manure

When you have your own horses, or source un-composted manure, you will need to compost it yourself before you use it.

First things first, remember the standard rules for good composting:

  1. For composting, you need to create conditions for micro-organisms to thrive, with the right temperatures, good aeration, and enough moisture but not too much.
  2. You need to add materials in the right ratio – balancing out the nitrogen-rich materials (like the horse manure) with carbon-rich materials (woody material, straw, dried leaves etc.).

Sometimes, the bedding used for the horses will serve well as the carbon-rich composting material.

Utilising Hot Composting

a tumbler used for hot composting

A hot composting system is recommended for composting horse manure.

Cold composting will take longer (around a year) and pathogens and weed seeds in the horse manure may still not be dealt with as effectively.

In a hot composting system, you will aim to achieve temperatures of at least between around 60 and 70°C inside the heap or bin over a sustained period of time.

The carbon to nitrogen ratio is important:

For best results, you should aim to add twice as much carbon-rich material as manure (by volume), or aim for a carbon-nitrogen ratio of around 25:1 (by weight), though this is just a rough rule of thumb.

Turn your compost to keep it sufficiently aerated and cover it during heavy rain to prevent excessive nutrient leaching.

How Long Does It Take?

Depending on a range of specifics, horse manure in a hot composting system can be ready to use in as little as 2 or 3 months.

When fully composted, horse manure should not smell bad, and should look and smell like soil or any other garden compost.

How & Where To Use It In The Garden

raised beds fertilised with manure in Autumn

Horse manure compost can be used just as you would use any other composted material in your growing areas.

Traditionally, gardeners dig well-rotted manure into their soil. However, we recommend taking a no-dig approach, which helps keep the soil ecosystem intact.

In no-dig gardening, compost is not dug in, but is spread as a mulch over the surface of the soil.

Simply add a layer of horse manure compost around your plants or across garden beds to prepare them in the early spring.

It can also be done in autumn in preparation for a winter crop. Aim to create a layer around 5-8cm deep.

horse manure in a wheelbarrow next to planting beds

Earthworms and micro-organisms will do the digging in for you, and over time, the organic material will be incorporated into the soil.

You can also top-dress raised beds, planters and containers in the same way.

You can also use horse manure compost, just like any other compost, to make a liquid plant feed for your organic garden.

Simply add composted horse manure to some water, strain the mix, and use it to give a boost to leafy plants.

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