Why Old, Rotted Manure Is Better for Growing Potatoes
Best Manure for Potatoes: Why Well-Rotted Manure Is Better 🥔💩
The golden rule: let it rot!
Potatoes need good soil to grow
If you’re growing potatoes, they’re going to need plenty of food to get those lovely tubers forming. And while fresh manure might look like the good stuff, when it comes to potatoes, old, well-rotted manure is definitely the better option.
Horse manure, chicken manure, well-rotted compost and even seaweed can all be useful additions to your potato-growing soil. Waste from small herbivores such as rabbits is also generally fine, provided the manure/bedding is suitable and composted where appropriate. The trick is knowing what to use, and when to use it.
Why not fresh manure?
Fresh manure is very strong stuff. It hasn’t had time to break down, so it can contain high levels of nutrients that may be too concentrated for growing plants.
It can also be hot enough to damage young roots and shoots. Fresh manure can contain plenty of ammonia and other compounds released as it decomposes, and it can even encourage unwanted weed growth if it contains viable seeds.
There’s another reason to avoid putting fresh manure directly around your seed potatoes: potatoes don't need to be sitting in a pile of fresh poo!
Give it time to rot down first and it becomes a much more useful soil improver.
Old manure is the good stuff
Well-rotted manure has had time to break down. It becomes darker, crumbly and much more pleasant to handle and, importantly, its nutrients are released more gradually.
It can help:
- Improve soil structure
- Add organic matter
- Improve moisture retention
- Improve drainage in heavier soils
- Provide nutrients as it continues to break down
- Encourage healthy soil life
And potatoes appreciate good soil. They need enough moisture and nutrients to produce a good crop, but they also need plenty of room for those tubers to develop.
Horse manure 🐴
Well-rotted horse manure is a popular choice for potato growers. It adds plenty of organic matter and helps improve the structure of the soil.
Chicken manure 🐔
Chicken manure is also packed with nutrients, which is exactly why you need to be a little careful with it.
Fresh chicken manure is particularly strong and shouldn't be used directly around growing potatoes. Well-rotted or properly composted chicken manure can be used, but use it sparingly.
If you're using a commercial chicken manure fertiliser, follow the application instructions on the packet. See the Royal Horticultural Society page for a good article on commercial chicken manure.
Seaweed 🌊
Seaweed can also be a useful addition to the garden. Whether you're using collected seaweed or a commercially prepared seaweed product, make sure you follow local rules about collecting it and allow fresh seaweed to weather or compost before using it around plants.
Seaweed isn't a replacement for everything your potatoes need, but it can be a useful source of organic matter and nutrients.
🐇 Rabbit manure
Rabbit manure is generally suitable for the garden. It can be added to compost or used around plants, although bedding material may need to be composted first.
🐹Gerbil/hamster bedding and droppings
Gerbil/hamster bedding and droppings can be composted, particularly if the bedding is untreated paper or wood-based material. However, check what the bedding contains and avoid anything treated, scented or contaminated with unsuitable materials.
❌⚠️ Dog and Cat Faeces ❌⚠️
Keep large domestic pet poo well away from your potatoes! 🐕💩🐈 Cat and dog faeces can contain harmful bacteria, parasites and pathogens that can survive in soil and potentially contaminate crops. ☠️Unlike well-rotted farmyard manure, pet waste isn’t suitable for adding nutrients to a vegetable patch. Compost your garden waste and use properly composted manure instead. Keep the pet poo for the bin, not the spuds!
⚠️ The big distinction is what the animal eats and what else is mixed with the waste. Avoid bedding containing chemicals, medication, cat litter or other unsuitable materials.
When should you add manure to potatoes?
There are two particularly useful opportunities: when planting and when mounding up.
When planting
Before planting your seed potatoes, work some well-rotted manure or compost into the soil.
You don't need to create a giant manure-filled trench , you're growing potatoes, not opening a spa for worms!
Mixing well-rotted organic matter into the soil helps create a good growing environment for your seed potatoes and gives the developing crop access to nutrients as it grows.
If you're growing potatoes in containers or grow bags, mix suitable well-rotted compost or manure into the growing medium rather than using fresh manure.
When mounding up
As your potato plants grow, you'll gradually add more soil around them. This is mounding up (or earthing up).
It's another opportunity to incorporate some well-rotted organic matter.
Add a layer of soil and well-rotted compost or manure around the plants, taking care not to bury all the foliage. As the plants grow, continue building up the mound.
Mounding helps cover developing tubers, gives the plants more growing room and helps prevent potatoes being exposed to light.
The golden rule: let it rot!
Whether it's horse manure, chicken manure or another type of organic material, fresh isn't automatically better.
When it comes to potatoes, give manure time to do its thing.
Well-rotted manure is easier on your plants, improves the soil and provides nutrients more gradually. Your potatoes will appreciate it, even if they don't particularly care whether their food comes from a horse, a chicken or the sea!
So, if you've got a pile of manure that's been quietly maturing in the corner of the garden, don't rush it.
Leave it to rot. Your potatoes will thank you. 🥔🌱
For more information about growing your potatoes, please see our growing guide.
Where can you get horse manure? 🐴
If you don't have your own supply, don't panic. You don't need to own a horse to get your hands on some well-rotted manure!
Try asking at local riding stables, farms or smallholdings. Many have more manure than they know what to do with and may be happy for you to take some away. Local gardening groups and community pages can also be a good place to ask.
Just remember that manure isn't necessarily free. Be prepared to make a donation or pay a small amount for a load, particularly if someone has gone to the trouble of loading it for you (and this is especially true if it is kids - give them a reward for their entrepreneurial spirit!)
And always ask how old it is. You want the good, well-rotted stuff rather than a fresh delivery straight from the stable! If it's still fresh, give it plenty of time to break down before using it around your potatoes.
A little bit of detective work locally could leave you with a very useful supply of organic matter and save a perfectly good pile of manure from going to waste. 🐴🥔
Things to watch out for
Manure is brilliant for the garden, but there are a few things worth checking before you start shovelling!
The smell: Fresh manure can be, well… fairly fragrant! 🐴💩 Properly rotted manure should have a much more earthy smell. If it still smells strongly of ammonia or looks very fresh, give it more time to break down.
Bacteria and disease: Manure can contain bacteria such as E. coli and other pathogens, particularly when it is fresh. This is another good reason to use well-rotted or properly composted manure rather than fresh manure. Wear gloves when handling it, wash your hands afterwards and avoid spreading fresh manure directly onto areas where crops are being harvested. If you're unsure about the source or how it has been stored, it's better to leave it alone.
What else is in it? Ask what's been used for bedding and what the animals have been eating. Horse manure often contains straw or wood-based bedding, while chicken manure may contain litter. Also be aware that some persistent herbicides can pass through animal manure and compost and damage crops. If the manure has come from horses that have been grazing or eating hay treated with certain herbicides, ask about this before putting it on your vegetable garden.
Weeds: Horse manure can sometimes contain seeds that have passed through the animal undigested. Good composting can reduce this problem, but you may still find the occasional bonus plant popping up!
So, know where your manure has come from, find out how old it is, and when in doubt, let it rot a little longer. Your potatoes won't complain about waiting. 🥔🌱
If space allows, it is best to use new compost / area for potatoes each year. Potatoes are a hungry crop and deplete many nutrients from the soil. In addition, using new soil prevents disease and pest build up. Planting potatoes in the same spot year after year lets fungal and bacterial diseases (like potato blight, scab, and verticillium wilt) multiply in the soil. Moving them starves these pathogens. Pests such as wireworms and cyst nematodes build up quickly if potatoes or related plants stay in one place.
The area that was used for potatoes can be used for legumes, brassicas or onion-family crops the following year.
Pictures on this page are (c) Lisa Patullo.
