What a load of old s***! Lets talk manure (and compost)

Animal dung (faeces) is a very traditional way of fertilising crops, but it can seem quite confusing! What manure is best to use on a vegetable garden? When should you add it? How much? What is the difference between manure and compost?

At Don’t Crop Me Now we predominately use composted horse manure to produce most of the mulch we use on our plots. We have a long-standing source of the manure that we are confident is weedkiller free (see Aminopyralid discussion below). Because we keep our own chickens we use their manure as component of our homemade compost. We have added guinea pig and rabbit manure/compost to our compost when we can source it. Recently I found a good few sacks of alpaca manure for a small donation to charity. I still have that stacked up in bags waiting for use!

Different types of manure: an analysis

Nitrogen (N), Phosporus (P) and Potassium (K) are the three basic elements required for plant growth. Obviously this is far simplified as plants do require other trace nutrients also, but these are the three biggies that are listed on ‘fertiliser’ nutrition. Allotment-garden.org has an interesting discussion on how these nutrients vary in different types of manures, however in reality it is very difficult to estimate this. It depends on the proportion of manure to bedding, water content of the manure and the stage of decomposition amoungst other factors. The important thing is that all animal manures are ‘complete fertilisers’. This means they have a good balance of N, P, K and also provide other trace elements.

The choice of type is a personal one. For us, chicken manure is a waste product from our own chickens so free and easy access! We use hemp bedding for our chickens and that also composts well. Horse manure supplies are plentiful in our area and a good relationship at our ground with a local riding stables means we can source a reliable supply; delivered at a very reasonable rate! Cow, small animal, sheep, alpaca and mixed farmyard manure would all be great for your vegetable plot! Look into supplies in your area and see what is avaliable! N.b. it is important to ensure you do not use manure from carnivores as that can introduce parasites into your compost that humans can be susceptible to.

What is the difference between manure and compost?

Really they are very similar! Compost is broken down organic matter. This could be plant or animal based or a mixture of both! Manure is animal dung (faeces) with or without their bedding. Therefore manure when left to break down = compost; hence you may hear the term ‘composted manure’. Both are great for the garden as a mulch (no dig) or to dig in if that is your sort of thing!

Adding manure or compost increases the organic matter of the ground which is great for microbial life in the soil. This drives fertility, but also creates good drainage and sound biological balance. In turn this will give you a healthy garden! Artifical fertilisers can boost nutrition of the ground, but they don’t increase the organic matter!

Homemade compost can be made from plant material, vegetable-based food waste, coffee grounds, paper, cardboard etc. There is no problem making compost from purely vegetable sources if that is important to you, but it works equally well with a mixture of animal manure and vegetable waste! We use a mixture of chicken manure/hemp bedding, vegetable/garden waste and paper/cardboard predominantly to make our own homemade compost.

When to use manure and how much to add?

There are many schools of thought on this. We add a layer of composted mulch (composted manure or homemade compost) from late Autumn to early Spring depending on when the bed is cleared of crops. At least 2 inches does well for us! If you have a large growing area (we have 500 square metres which recently increased to 625 square metres!). Even 2 inches is a very large volume. We can’t make that much compost (realistically). We produce about 2-4 tonnes of homemade compost and then bring in about 6-8 tonnes of composted horse manure from a local riding stable who deliver to our allotment ground.

Making liquid manure

Manure can be added to water to produce a liquid feed which is great for feeding plants throughout the growing season. If you have mulched well it isn’t essential, but flowering plants like tomatoes do like a good liquid boost! Add a small amount of the manure of your choice (say a trowel full) to every 10L (ish) of water.

Aminopyralid in manure

Aminopyralid is a type of weedkiller (herbicide) that is found in some lawn weedkillers as well as some agricultural products. It is used to kill broad-leaved weeds in grassland. This herbicide can pass through animals without breaking down. Therefore manure from animals fed on treated grass can contain the residue and damage crops.

The weedkiller is broken down by soil bacteria, but this does take time. In most cases this is around 1 year when spread and up to 2-3 years in heaps of manure. That does mean it is important to carefully check that your source of manure has come from animals that have not fed on areas of grassland that has been treated with aminopyralid. Before spreading manure on your growing area try testing growing a bean seed to ensure the young plant looks healthy. Typical symptoms include cupped leaves and fern-like growth with stunted growth meaning crops are unusable. Potatoes, beans and tomatoes are particularly senstive to this weedkiller whilst pumpkins and squash can be relatively unaffected.

In summary

Compost, or composted manures, are a very important component of a healthy vegetable garden. They increase the organic matter of the ground which drives healthy microbial life thus healthy soil! Making your own compost (with or without manure as a component) is also great for your garden. If you have a big area bringing in manure can be a good way to increase your volume, but it is important to check your sources of manure to ensure it is weedkiller free.