Composting horse manure: how to do it right

Why composting pays off for horse owners

Horse manure is naturally richer in carbon than cattle manure, due to the straw or sawdust used as bedding. That makes it less suitable for spreading directly on land — raw manure draws nitrogen from the soil as it breaks down. Composting solves that problem. After 3 to 6 months of composting, the manure is stable, smells earthy rather than of ammonia, and is safe for direct use. An added benefit: the volume decreases by 40 to 50 percent, making removal and storage considerably easier. What's more, proper composting significantly reduces the survival of worms and parasites in the manure.

The right location and structure for your heap

Choose a flat, paved surface with good drainage — preferably at least 10 metres from waterways and 25 metres from inhabited buildings. A three-sided enclosure made from pallets or concrete slabs works best. Ideally, use three bays side by side: one for fresh manure, one active composting heap, and one for mature compost. Each heap needs a minimum volume of 1 m³ to generate sufficient heat. Larger heaps of 2 to 3 m³ perform better and reach temperatures of 55 to 70 degrees Celsius more quickly, which kills parasites and weed seeds.

What to add — and what not to add — to your heap

Not everything belongs in your compost heap. Follow these guidelines:

• Do add: manure with straw or sawdust, green waste, hay and grass cuttings, old silage grass
• Do add: water if the heap feels too dry (ideal moisture level: compressed material just barely doesn't drip)
• Don't add: manure from animals that have recently been wormed — wait 2 to 4 weeks after treatment
• Don't add: large quantities of wood chips at once — these slow down the decomposition process
• Don't add: plastic, rope, or packaging material — these contaminate the finished compost

Temperature and turning: the key to success

The core of the composting process is heat. In the first few weeks, the temperature in a well-built heap rises to 55–70 °C. After 3 to 4 weeks the heap begins to cool down — that is the moment to turn it. Use a manure fork and bring the outer material to the centre. Turning introduces oxygen into the heap, which revitalises the bacteria and speeds up decomposition. Plan to do this every 3 to 4 weeks, at least 2 to 3 times per composting cycle. You can measure the temperature with a compost thermometer. Record your turning dates in the horse profile in EquiSight so you can track the process without anything slipping through the cracks.

When is your compost ready to use?

You can recognise mature compost by a number of characteristics:

• Dark brown to black in colour, crumbly texture
• Smells like forest soil, no longer like manure or ammonia
• No recognisable straw or other material still visible
• Temperature has dropped to ambient temperature and no longer rises after turning
• Volume has decreased by approximately 40–50 percent compared to the starting mass

Regulations and practical considerations

In the Netherlands, horse manure falls under manure legislation. More lenient rules apply to private individuals with fewer than 3 horses on their own land, but as soon as you remove or sell manure, you must register this correctly. If in doubt, contact the RVO for up-to-date information. Professional stables are required to keep a manure record. Use the calendar and horse profile in EquiSight to document manure removal and composting rounds. This way, during an inspection you have everything immediately to hand and don't need to search through old notes or emails.