Which manure is best for a garden — horse, cow, chicken or sheep?

Manure does two jobs at once — bulky organic matter that improves structure, and nutrition — and the different animals sit at different points on that spectrum. Underneath that, the bedding it comes mixed with changes the material more than the species does, and the risk of herbicide residue varies with what the animal was fed rather than with what it is.

Safety

Step by step

1. Assess horse manure.The most widely available, usually free from livery yards. Moderately rich, bulky, rots reasonably fast on straw and slowly on shavings. Excellent general soil improver for clay and for hungry vegetable ground. Its weakness is risk: horses are fed bought-in hay whose origin nobody tracks, which makes it the highest aminopyralid risk of the four.
2. Assess cattle manure.Wetter, finer, lower in nitrogen and slower-acting than horse. It rots to a dense, dark material that holds water well, which makes it the better choice on sandy or free-draining soil. Farmyard manure sold in bags is usually cattle-based. Residue risk is real but generally lower than horse, because more cattle are on home-grown forage.
3. Assess poultry manure.Not a bulk soil improver at all. It is a concentrated nitrogen and phosphorus fertiliser with some organic matter attached — several times stronger than horse manure by weight. Use it as a feed, at a fertiliser rate, not as a mulch. Fresh, it will kill anything it touches. Housed birds on a grain diet mean the residue risk is the lowest of the four.
4. Assess sheep manure.Richer than cow, drier, in small pellets that break down readily. Very good material where you can get it, which for most gardeners is rarely. Sheep on unimproved pasture are a low residue risk; sheep on treated grassland are not.
5. Then look at the bedding, which matters more.Straw-based manure rots in six to twelve months and adds nitrogen. Wood shavings and sawdust bedding is high in carbon, takes eighteen months or more, and will lock up nitrogen if used before it is finished. Paper and cardboard bedding sits in between. A straw-bedded horse manure and a shavings-bedded one are different products.
6. Weigh the availability against the ideal.The best manure is the well-rotted, tested one you can actually get. A local yard giving away straw-based horse manure that passes a bean test beats a theoretically superior material you have to pay to have delivered from forty miles away.
7. Test whatever you choose.Species tells you about strength and speed. It does not tell you about residue. Run a bean bioassay on any manure going onto a vegetable plot, whichever animal it came from.
8. Match the material to the job.Bulk soil improvement on clay: horse. Water holding on sand: cow. Feeding a hungry crop: poultry, at a measured rate. Surface mulch around ornamentals: any of them, well rotted.

Tips

• Bagged 'farmyard manure' from garden centres is usually cattle-based and quite finely composted — closer to a rich compost than to raw manure, and priced accordingly.
• Zoo manure, sometimes sold at open days, is generally herbivore manure with the same properties as farm manure and an interesting provenance. The same rotting and testing rules apply.
• Rabbit and guinea pig bedding from your own animals is excellent, safe, low-risk and available in small quantities — ideal for a small garden or for adding to a compost heap as nitrogen.
• Mushroom compost is often grouped with manures because it is manure-based, but it is alkaline and behaves quite differently. It is a separate decision.
• If a yard will not let you take it from the middle of the heap, take from wherever they allow and stack it yourself for another six months.

Alternatives

• Garden compost: No residue risk if your inputs are clean, free, and improves structure just as well. Lower in nitrogen than manure, so hungry crops still want feeding separately.
• Municipal green-waste compost: Cheap in bulk and consistent. Choose a certified producer working to a recognised quality protocol, which controls what goes in and audits the process.
• Leaf mould: The safest bulky material there is and free if you have trees. Low in nutrients, superb for structure and water holding, and it settles less than compost.
• Composted bark: Slower to break down, so it holds soil open for longer as a mulch. No nutrition to speak of, and no contamination risk.

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