If you’re new to gardening, you’re probably interested in using organic quality compost or manure, but not sure which to choose. Making your own compost is confusing enough, but when you add manures and fertilizers to the mix, there’s an overload of information.
So what is compost exactly, and how is it different from manure?
There is one very obvious difference between manure and compost – its origin. Manure is animal dung and a by-product of livestock farming, usually a mixture of faeces and urine. Compost is more varied but typically made from grass clippings, kitchen waste, leaf litter, cardboard and plant material.
In this article we want to move beyond that obvious difference and look at the mineral make-up, the nutrient ratios, and the efficiency and safety of manure vs. compost, keeping an open mind to some alternative products too, because just like you, we’re gardeners on the eternal search of the best growing mediums.
What is the difference between manure and compost?
There are three major differences between manure and compost, beyond their origins:
- nutrients;
- safety;
- speed of nutrient release.
For clarity, we’ve split the macro-nutrients – Nitrogen, Phosphorous and Potassium – out from the micro-nutrients and minerals so the differences are clearer.
The nutritional difference between manure and compost
The most common manure used in gardens is horse manure. It’s the easiest to harvest, and least damaging to the environment as it’s a by-product of pet and sports animals, rather than farmed animals. So to compare the nutritional difference between horse manure and compost, they are actually strikingly similar.
- Horse manure’s NPK is 0.7/0.3/0.6
- Compost’s NPK is 0.5/0.3/0.8
So while manure has more nitrogen, and is more capable of supplying roots with that nitrogen thanks to higher acidity, its potassium and phosphorous levels are virtually identical to compost.
The big difference is in how it is supplied to the roots. Manure’s nitrogen is mostly carried in ammonia (ammonium nitrate). This has higher acidity than basic nitrogen, and the plant’s roots take its nutrients more easily in slightly acidic conditions.
The mineral difference between manure and compost
Magnesium, calcium and sulphur are typically classed as micro-nutrients when we talk about composts and fertilisers as they’re delivered in very limited supplies, but manure from mammals and birds (cows, rabbits, pigs, horses, sheep, chickens, etc.) contains these minerals in much higher quantities than compost.
In some cases, the higher mineral values are useful, particularly for soft-leaved lettuces, and climbing greens like Malabar spinach, but for most vegetables overusing manure can lead to excessive calcium and burned roots because of the high ammonia and sulphur.
Provided you allow fresh manure to rot fully before use, sulphur and ammonia content can be dramatically reduced.
Is compost or manure safer in the garden?
Compost can harbour bacteria and lead to food poisoning if poorly aerated, but with less severity, so it’s a generally safer alternative to cow or horse manure.
Different manures have different properties, but hot manures like cow and horse manure can carry Escherichia coli (E. coli). While most E. coli are harmless, and humans typically carry E. coli in our intestines, some strains can cause kidney failure or food poisoning.
Those strains are not rare in cow or horse manure and can infect crops if they’re not properly washed, or manure is not properly prepared.
Does Alpaca manure contain E. coli?
Over the last few years, alpaca manure, and alpaca farms in general, have become more mainstream, but research into their manure, wool and effects as farm animals has not been strongly proven.
Many alpaca breeders claim there have never been E. coli infections related to alpaca manure, which would be a great advance for gardeners, but in reality, every mammal carries E. coli and can pass on the harmful E. coli 157 strain.
What works faster, manure or compost?
Manure’s nitrogen release is incredibly fast-acting on crops of all ages, while compost is generally used as a slow-release fertilizer, and has a less direct impact on the roots.
One clue to manure’s efficacy is its regular use in soil improvers. Thanks to its higher acidity, manure is a great way to boost overall plant health and increase nutrient uptake in the roots of plants, provided those plants like slightly acidic soils.
Because manure raises acidity, it is a more effective all-around plant support than compost.
Should you use fertilizer or manure?
Fertilizers have higher NPK ratings than manure and compost, but that doesn’t mean they feed as effectively. If you water any dry pot, you’ll see water drain from the bottom pretty quickly – this happens in the soil when using liquid feeds.
Fertilizer has high NPK ratings because it needs big ratios to make sure some sticks around the roots, whereas manure and compost are slow-release, reliable fertilizers.
In an ideal world, plants would get all their nutrients from the soil as they would in nature, but we live in cooler climates and our soil is less fertile so we rely on these methods of fertilization more than we care for.
Manure, compost, or fertilizer – what to use?
When to use compost instead of manure
You should use compost instead of manure whenever you are growing root vegetables or starting seedlings. Manure can be too strong for tender plants, or annual vegetables, but root vegetables, in particular, can have very strange interactions with manure.
If you dig manure through a raised bed for carrots, those carrots will likely fork, the same with parsnips, beetroot and even celeriac. Any tough root vegetable that is over-fed will react in strange ways to manure, so wherever possible you should sow root veg in pots of compost and sand so drainage is improved, and nutrients are reduced.
Also, annual fruits like tomatoes, aubergines and cucumbers prefer compost to manure. Manure can be too strong, even when rotted for these fruiting plants, where nitrogen isn’t key to their success.
When to use manure instead of compost
Manure is a great default mulch for allotments and vegetable gardens, and mulching between growing periods is a great way to improve soil health. Even fresh manure can rot down as a mulch in autumn when crops are finished. You can plant straight into the bed in spring.
- Leafy salads
- Beans / Grains & Pulses (incl. sweetcorn)
- Squashes
- Potatoes / Tubers
The only vegetables that enjoy a repeat treatment of manure are salad crops, which are hungry plants that require high water retention, lots of light, and lots of nutrients. By creating a manure feed (mixing manure with water) you’ve got a tidy way to feed salad crops without mulching around delicate plants. Feed them once a week in this way.
Squashes, sweetcorn and beans love manure too, but only as a starter fertilizer, either dug into the soil or added to the planting hole. As fast-growing annual crops, they need to establish lots of leaf and healthy root systems before they begin flowering and fruiting, so manure gives beans and squashes a useful boost.
When to use fertilizer instead of manure or compost
While tomatoes can benefit from added nitrogen and prefer slightly acid soil, manure can be too strong for their tender stems, especially as young plants. Even a simple garden compost can over-fertilize and lead to leggy plants if used too early in their growing stages.
- Vegetables, where the fruit is the goal rather than the leaf or root, will prefer fertilizers to manure.
- Compost can be useful for annual fruits (tomatoes, aubergines, peppers, cucumbers).
- Tender perennial fruits can be mulched with manure in winter, to protect their roots from frost.
Where to buy manure
Manure is relatively easy to find in garden centres or DIY stores, but there is no better place to find manure than straight for the farm.
Cow or horse manure from the farm is not rotted, and will need to be stored for around 4-5 months before use, but can be bought for a fraction of the price. Alpaca manure is typically expensive but has less ammonia so can be used after 1-2 months.
What to look for when buying manure
We’re not in the 1950s anymore, and no one’s walking after the police horse collecting manure for their allotment in 2022.
Rotted manure is incredibly easy to come by these days, with mail-order manure available online, in bulk, or in small manure bags. Rotted manure is more expensive than fresh though, as with fresh you have to do the work yourself.
You can find cheap fresh manure from local farms, and livestock farmers are often desperate to get rid of the stuff. By far the best way to find manure though is to join an allotment society. For the cost of an annual membership, many provide manure for free.
What is the best manure or compost for the garden?
| N (Nitrogen) % | P (Phosphorous) % | K (Potassium) % | |
| Garden Compost | 0.5 | 0.3 | 0.8 |
| Cow manure | 0.6 | 0.4 | 0.5 |
| Horse manure | 0.7 | 0.3 | 0.6 |
| Pig manure | 0.8 | 0.7 | 0.5 |
| Chicken manure | 1.1 | 0.8 | 0.5 |
| Chicken manure pellets | 4 | 2.5 | 2.3 |
| Sheep manure | 0.7 | 0.3 | 0.9 |
| Rabbit manure | 2.4 | 1.4 | 0.6 |
| Alpaca manure* | 1.5 | 0.7 | 1.1 |
- *Note: Alpaca manure has no formal studies into its composition and effects, so these NPK ratings are averages from alpaca manure sellers and may not be truly comparable to other ratings.
For general purpose feeds, manure and compost are both perfect, but it’s important to understand the ammonia and sulphur content in each when choosing a general-purpose compost or mulch for the garden.
Nitrogen is the key indicator of ammonia in manures, with all apart from rabbit droppings containing almost 15% ammonia, which can quickly burn your plants.
To avoid the risk of ammonia burns, compost is the safest bet, and the easiest to make yourself, but chicken manure and rabbit manure are both gentle to crops, and when used sparingly provide a wonderful and safe plant food.
Conclusion
Manure might not seem like a particularly exciting subject, but when you dig into it (pun intended) it’s full of fascinating microorganisms, and natural ways to improve plant health. Choosing between compost and manure depends entirely on what you’re growing.
While I can’t give you a simple answer to what is better – manure, compost, or fertilizer – you’re now familiar with the difference between compost and manure. Hopefully, that means you’ll make space for a proper manure stack in the garden so you can create your own rotted manure.
