How to Use Animal Manure Safely in the Garden
Animal manure can add organic matter and useful plant nutrients to garden soil. When obtained from a reliable source and used appropriately, it can improve soil structure, support soil organisms and help feed demanding crops.
However, manure varies enormously. The animal, bedding, storage conditions and age all affect the finished material. It should never be treated as a perfectly measured fertiliser.
Which animal manures can be used?
Common garden manures include:
Horse manure
Cow manure
Sheep or goat manure
Rabbit manure
Poultry manure
Manure from herbivorous animals is normally suitable after appropriate handling. Do not use waste from dogs, cats or humans on food-growing areas because of the greater risk from pathogens and parasites.
Always ask whether the animals have recently received medication and whether their bedding or feed may contain herbicide residues.
Fresh manure and well-rotted manure
Fresh manure may contain high levels of readily available nutrients, particularly nitrogen and ammonia. It can damage plant roots, scorch foliage and introduce pathogens or viable weed seeds.
Well-rotted manure is dark, crumbly and no longer smells strongly of fresh waste. The original manure and bedding should be difficult to distinguish.
In most vegetable gardens, rotted or composted manure is safer and easier to use than fresh material.
How to compost manure
Build a contained heap using manure mixed with its straw, hay or wood-based bedding. The bedding supplies carbon and creates air spaces, while the manure supplies nitrogen and moisture.
The heap should be moist but not saturated. Covering it helps retain moisture and prevents heavy rain from washing nutrients away.
Turning the heap introduces air and encourages more even decomposition, although an unturned pile will still rot down given sufficient time.
Allow the manure to mature until it becomes dark and earthy-smelling. This commonly takes six months or longer, depending on the material, temperature and management.
Be alert for persistent herbicides
Some livestock feed and bedding may contain residues of persistent weedkillers. These chemicals can pass through an animal and remain active in manure or compost, damaging sensitive plants such as tomatoes, beans, peas and potatoes.
Before spreading unfamiliar manure widely, carry out a simple test:
Fill several pots with a mixture containing the manure.
Fill the same number of pots with trusted compost as a comparison.
Sow peas or beans in each pot.
Observe the new growth for several weeks.
Twisted, curled or unusually narrow leaves may indicate herbicide contamination. If the test plants are affected, do not use the manure on the garden or add it to compost intended for growing plants.
Pathogens and food crops
Fresh manure can carry harmful bacteria. The risk is greatest when it contacts crops eaten raw, particularly leaves and roots close to the soil surface.
Use thoroughly composted manure whenever possible. Keep it away from edible leaves and fruits, wash harvested produce carefully and practise good hand hygiene after handling manure.
If fresh manure must be used, apply it well before sowing or planting rather than around a crop approaching harvest. Local food-safety guidance may specify minimum intervals, so check the rules applying in your country if you grow food commercially or for other people.
How much manure should you apply?
A surface layer around 2–5 cm deep is enough for many beds. More is not automatically better.
Repeated heavy applications can cause excessive levels of phosphorus and other nutrients. This may reduce plant health and allow nutrients to leach or wash into waterways.
Observe crop performance and, where manure has been used regularly, consider a soil test before adding more.
Which crops benefit from manure?
Well-rotted manure is particularly useful for nutrient-demanding crops, including:
Squash and pumpkins
Courgettes
Brassicas
Sweetcorn
Celery
Established fruit bushes
Root crops such as carrots and parsnips often grow better on ground manured for a previous crop. Very rich or recently manured soil can encourage forked roots or excessive leafy growth.
Beans and peas can obtain nitrogen through their association with soil bacteria and may not need rich manure applications.
Using poultry manure
Poultry manure is usually more concentrated than horse or cow manure. Fresh material can be particularly strong and should be composted with plenty of carbon-rich bedding or other dry material.
Commercial pelleted poultry manure is easier to measure but is still concentrated. Follow the stated application rate and avoid assuming that an organic product cannot be overused.
Using manure as a surface mulch
Spread mature manure over the soil surface rather than automatically digging it in. Earthworms and other organisms will gradually incorporate the material.
Surface application protects soil structure and reduces unnecessary disturbance. Apply it when the ground is moist, and keep very rich material away from direct contact with young stems.
Manure can also be mixed with other compost ingredients when you want a more balanced, less concentrated material.
Storing manure responsibly
Keep manure away from wells, streams, drainage channels and areas likely to flood. Cover the heap to reduce nutrient loss and prevent runoff during heavy rain.
A contained storage area makes the material easier to manage and prevents it spreading into paths or neighbouring land.
If the heap becomes dry, add a little water. If it becomes saturated or smells strongly unpleasant, introduce dry bedding and improve drainage or airflow.
Use manure as one part of soil care
Manure can be valuable, but a healthy garden does not depend on it. Garden compost, leaf mould, chopped plant material, mulches and living roots all contribute to soil health.
Use manure from a known source, allow it to mature, test unfamiliar material and apply only as much as the soil and crops need. Careful use provides the benefits while reducing risks to plants, people and the wider environment.
