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What is Compost and How to Use It

When made correctly, compost is free organic fertiliser for your plants that not only contains valuable nutrients but also important soil microbes.

Many gardeners around the country understand the benefits of creating and using compost in their gardens.

Essentially, composting is the art of breaking down organic waste both from the kitchen and the garden into soil that is packed with nutrients.

What is compost?

compost and food scraps | Plant care

Compost is what you get when you let organic waste such as vegetable scraps, dried leaves, and grass clippings sit for some time in a heated environment until it breaks down to create a nutrient-dense soil additive.

When made correctly, compost is free organic fertiliser for your plants that not only contains valuable nutrients but also important soil microbes.

It’s even better if your compost has encouraged worm activity as these will then end up in the garden to benefit your plants.

What is compost used for?

Compost is used to give your plants valuable nutrients and to create a premium growing environment.

Essentially, you’re using a natural material that you’ve created to give your plants the goodness that they need.

You can use compost by adding it to your garden beds where you grow vegetables and flowers. You can also mix it with some other potting mix ingredients to use in all of your potted plants.

How to use compost in your garden

Compost 2 | Plant care

Before you can use compost in your garden, you have to make some. This is fairly easy and there are plenty of ready-made compost bins that you can purchase for this purpose.

Most compost bins are made from heavy-duty black plastic as this is both durable and attracts heat from the sun. This heat helps to break down the organic waste faster. 

Once you have your compost bin set up, all you have to do is add all of your organic kitchen scraps, leaves that you’ve raked up in your garden, and your grass clippings. 

When the organic waste has broken down sufficiently, you’ll end up with a rich, dark soil-like product. You can now add this to your growing beds. 

Generally, I like to top my vegetable beds with a layer of compost before planting the next crop. This means that my vegetables get an extra boost of nutrients right from the start.

If you have plenty, you can also spread compost around your fruit trees and other ornamentals to give them a boost of nutrients. Just take care not to place it around some of your native plants because many don’t appreciate a lot of phosphorus in the soil.

How to use compost in potted plants

pot plants | Plant care

If you want to use compost in your potted plants, you can do this in two ways. If your plants are already growing in potting mix, it’s fine to add a layer of compost to the top of the soil in the pot.

Potting mixes tend to settle over time and the plants will deplete all the nutrients that were in the mix, to begin with. Adding a layer of compost to the top not only adds additional nutrients but also replenishes the soil.

Another thing that you can do is make your own potting mix using compost, sand, and coconut coir. By mixing these ingredients together in equal parts by volume, you can create a nutrient-rich mix that your potted plants will love.

This is actually one of the best types of potting mix that you can create yourself because the compost adds the nutrients, the sand helps with drainage and the coconut coir helps the mix to retain moisture.

You could even consider adding some compost to any commercial potting mixes that you buy. This helps to bulk up the mix so that it goes further and also adds additional nutrients. It’s also a great way to save money because the compost that you create yourself is free.

Planting into compost

Many gardeners will tell you that you should dig your compost into the soil before planting. However, I never do this and my plants are happy and healthy. 

With my vegetable beds, all I do is add a layer of compost over the top of the existing soil and then, just lightly rake it over with a three-pronged cultivator. I then let the bed sit for a week or two before planting my next crop of vegetables.

For fruit trees that are grown in large pots, I simply add a layer of compost to the top of the soil and water as normal.

As a tip, I also like to add a little wood ash to fruiting trees, especially citrus. As a result, my potted lime tree has a massive amount of blossoms this year!

How much compost to add to soil

fresh compost | Plant care

You can never add too much compost. After all, compost is just nutrient-rich soil.

It’s very similar to the topsoil that you’ll find in a large forest. This topsoil has been created by the decomposition of all the green matter that has fallen from the trees and other forest plants.

Therefore, how much you add will depend on how much you have available and how far it needs to spread. Even a thin layer of compost will be beneficial but a moderate layer that’s around 5 to 20 centimetres thick will be perfect.

When should you apply compost?

You can apply compost at any time of the year. The perfect time is when your vegetable beds have finished with one crop and are waiting for the next crop to be planted.

However, don’t be afraid to add some compost around your existing plants any time you have some available.

What is the best compost for a vegetable garden?

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The best compost for a vegetable garden is compost you’ve made yourself from organic kitchen scraps and garden waste.

It’s free fertiliser and will give your veggies the perfect growing environment.

You can also add some aged manure to the compost as it’s cooking to add even more nutrients and goodness.

Compost vs fertiliser

In essence, compost is a natural and totally organic fertiliser. It should contain all the nutrients your plants need without the need for adding any additional fertiliser.

Compost is also unlikely to expose your plants to fertiliser burn as many inorganic fertilisers can. 

Therefore, using compost is simply the best way to give your plants all that they need to grow happily in your garden.

Compost vs manure

Compost is very much like natural manure because it has been created from broken-down organic matter.

In fact, you can even add some aged animal manure to your compost as this will help to heat it up and break it down even quicker.

But if you have plenty of compost to add to your garden, you don’t really need to add manure as well.

However, some plants are very heavy feeders so they may benefit from a little aged manure as well as the compost.

Compost vs mulch

mulch around plant | Plant care

Compost and mulch have separate purposes. Compost is used as an addition to your soil and helps support your plants with plenty of healthy nutrients. It also helps to improve the overall soil structure.

On the other hand, mulch is used as a covering over the soil to prevent moisture loss and to help regulate the soil temperature.

Therefore, you should use both compost and mulch in your garden.

In addition, a lot of organic mulches will eventually also break down, just like the compost, and this will improve the structure and nutrient content of the soil even further.

FAQ

Can plants grow in compost only?

Absolutely. Compost is just like topsoil and is full of goodness for plants. Of course, you want to ensure that the compost is completely cooked and not still decomposing. You also don’t want to grow native Australian species in compost.

What are the disadvantages of composting?

Personally, I don’t see any disadvantages of composting apart from the initial cost of purchasing the compost bin and the wait time before the compost is ready to use.

Photo of author

Annette Hird

Annette Hird is a gardening expert with many years of experience in a range of gardening related positions. She has an Associate Diploma of Applied Science in Horticulture and has worked in a variety of production nurseries, primarily as a propagator. She has also been responsible for a large homestead garden that included lawn care, fruit trees, roses and many other ornamental plants. More recently, Annette has concentrated on improving the garden landscape of the homes that she has lived in and focused a lot of energy on growing edible plants as well. She now enjoys sharing her experience and knowledge with others by writing articles about all facets of gardening and growing plants.

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