Why bother composting manure?

Fresh manure is a wonderful resource, but it is not ready for vegetable beds. Applied straight, it can scorch young roots, spread weed seeds, and carry pathogens such as E. coli, Salmonella and Listeria. Composting transforms it. The heap heats up, beneficial microbes break down bedding and droppings, and the result is a crumbly, earthy material that feeds soil life without the risks. On a smallholding, where every barrowload matters, composting manure is one of the best returns you can get for a bit of stacking and turning.

Getting the carbon-to-nitrogen mix right

Manure is high in nitrogen; straw and other bedding are high in carbon. Aim for roughly 25–30 parts carbon to 1 part nitrogen by weight. In practice, that means mixing about three to four parts straw or bedding to one part droppings. If you keep horses, the muck heap often arrives already mixed. Poultry and pig manure are richer, so add more straw, shredded paper, or spent bedding. Cow manure is wetter and denser, so mix in chopped straw or woodchip that has already been composted once.

• Horse and cow manure: usually well balanced with bedding; add straw if sloppy.
• Chicken and pigeon manure: very strong; use no more than one part to four parts straw.
• Goat and sheep manure: pellet-like and easy to stack; add a little water and green waste.
• Avoid dog, cat and pig waste for vegetable beds because of disease risks.

Building and managing the heap

Choose a level spot away from watercourses and wells, ideally on bare soil or a pallet base so worms and microbes can move in. Build in layers 15–20 cm deep: manure, then straw, then a thin sprinkle of soil or old compost. Water each layer as you go until it is as damp as a wrung-out sponge. For a hot heap, size matters: aim for at least 1.2m x 1.2m x 1.2m. Smaller heaps may never heat up properly, while larger ones can go anaerobic in the middle.

Cover the heap with a breathable tarpaulin or a thick layer of straw. This keeps rain from leaching nutrients and stops the surface drying out. Do not seal it completely; the heap needs some air. If you have several bays, turn from one into the next. If you only have one heap, turn it in place by pulling the outside to the middle and the middle to the outside.

Turning, temperature and moisture

Heat is the sign that composting is working. Use a compost thermometer or push a metal bar into the centre and feel it. A good heap reaches 55–65°C for several days, which kills most weed seeds and pathogens. Turn when the temperature drops below 40°C, or every two to three weeks for a slower heap. Turning moves cooler outer material into the hot core and gives the microbes a fresh supply of oxygen.

Check moisture each time you turn. If it is too dry, water gently as you rebuild. If it is too wet and smelly, add straw, shredded cardboard or dry leaves. A well-managed heap should smell earthy, not sour or ammonia-rich. In wet UK winters, a cover is essential; in dry summers, you may need to water more often than you expect.

Maturing, testing and using it

After the hot phase, let the heap mature. Six months is a minimum; twelve months is better, especially for beds growing root crops or salads. Mature compost is dark, crumbly and sweet-smelling, with few recognisable bits of straw. Store it under cover in bags or a covered bay until you need it.

Before spreading, test for aminopyralid or clopyralid residues from hay or straw. Fill a small pot with the compost, sow broad beans or tomatoes, and watch for twisted, cupped or fern-like leaves. If you see those signs, do not use it on vegetable beds; spread it on paths or leave it to break down for another year.

Apply well-rotted manure in autumn for heavy feeders such as courgettes, brassicas and leeks, or as a spring mulch around fruit bushes and perennials. A 5cm layer is plenty. For general beds, one to two barrowloads per 10 square metres is a generous dose. Dig it into the top 15cm or leave it on the surface for worms to pull down.

Common pitfalls and how to avoid them

• Using fresh manure: wait until it is fully rotted and crumbly.
• Letting the heap dry out: cover it and water when you turn.
• Adding too much nitrogen: balance poultry muck with plenty of straw.
• Forgetting to turn: unturned heaps may stay cool and leave weed seeds alive.
• Spreading on frozen or waterlogged ground: nutrients will run off. Wait for a dry spell.

Composting manure is not complicated, but it rewards attention. Stack it well, keep it damp, turn it when it cools, and let it mature. Your vegetable beds will thank you with stronger growth, healthier soil and fewer weeds.