Gardening Advice

How to Use Compost in Your Garden

alicja neumiler /

Autumn days in Australia are numbered, and with them the window for composting is slowly coming to a close. Compost consists of decomposed organic matter, rich in beneficial nutrients for plants, but that’s not all there is to it.

The benefits of compost are way too many. In short, it can amend soil, improve water retention, enhance aeration and even combat climate change! How cool is that?! Keep reading to learn more about how the magic happens, what compost is used for and how to use it in your garden.

Table of contents:

Benefits of using compost in the garden

It might seem slightly exaggerated, but in reality, compost has so many advantages that its nickname “Gardener’s Gold” doesn’t do it enough justice. Compost helps feed your plants and maintain a high level of beneficial bacteria in the soil with its structural, biological, and chemical benefits. Plus, it helps form humus – the adhesive that makes healthy soil stick together. To answer the question “What is compost used for?” here are the main benefits of compost, explained:

  • Conserving water – The Gardener’s Gold can control and reduce the water flow through and on your soil to help increase water absorption. That way, water soaks into the ground and stays there longer, allowing your plants to receive the optimal amount of water.
  • Enhancing all soil types – Compost works wonders with sandy soil’s weak moisture retention, while clay soil gets better compaction and drainage. Compost also helps protect silt, which is prone to erosion from the wind.
  • Promoting healthy plant growth – It’s not just about structure. Composting balances soil density and pH and increases the soil’s capacity to exchange nutrients. On top of that, it can protect your plants from both pests and diseases. And did we mention it discourages weed growth?
  • Reducing maintenance costs – In the long term, compost reduces the cost of maintaining your garden. The benefits of composting reduce plant mortality, which saves you both money and time from re-planting. Another bonus you get from compost’s water mastery is that you spend less time and money on irrigation.
  • Reducing waste – On top of all the personal benefits, compost is also beneficial to the environment. It’s made of organic waste, which would otherwise be transported to a landfill, emitting considerable amounts of carbon dioxide. The waste wouldn’t have decomposed for decades in the landfill due to the plastic bags people use for waste containment.
  • Tackling climate change – Compost can both reduce and absorb greenhouse gasses. Reducing the amount of waste in landfills prevents methane emissions, and promoting healthy plants helps cleanse the atmosphere from carbon dioxide faster.
  • Stormwater management – Another benefit that stems from composting’s incredible functionality with water is that it can benefit landscape infrastructure projects with stormwater hydrology. Hence, large open areas have an easier time supporting healthy vegetation. Quite the benefit, considering how rainy it gets during the wet season in Australia.
  • Wetland reclamation efforts – Wetlands are beautiful environments that provide food and shelter for many animal and plant species. However, many human activities can pollute them, causing disruptions with catastrophic consequences to their ecosystems. That’s why government organisations promote the implementation of compost as a defensive layer between pollutants and sensitive ecosystems.

Obviously, there is a considerable number of composting benefits. Combined with other practices that improve your soil’s quality, you can use it to make all the neighbours praise your gardening skills.

How to know your compost is ready to use

First things first, premature compost is a bad idea. You will attract pests and damage your soil and plants. But when is it ready to use? What does finished compost look like? There are a few things to check before you add it to your garden:

  • Texture – It should feel smooth and crumbly when you pick a handful. You shouldn’t be able to recognise the kind of organic matter it used to be – leaves, shells, sticks etc. Depending on how your compost was made and what ingredients were used, you might have to remove larger pieces that take longer to decompose. (e.g corncobs)
  • Colour – Your compost should be dark brown or darker. The colour should be rich and consistent throughout the entire pile, both inside and out.
  • Smell – The aroma of mature compost should be reminiscent of forest soil. The scent should be fragrantly sweet. There shouldn’t be any trace of sour odours, like ammonia.
To check your compost, put some in a sealable plastic bag, push the air out, and seal it. After 3-4 days, open the bag and smell it. If it smells anything like ammonia, then it isn’t ready yet. Give it two more weeks and check again.

How to use compost

Now that you know how many benefits composting brings to the table, and how to tell if it’s ready – it’s time to learn more about when and how to use compost.

The first thing gardeners wonder about is when to use compost – the best time is during the autumn. Your soil will have enough time to saturate with nutrients and prepare for planting in the spring. You should aim to reinforce your garden with compost once or twice a year. If your compost isn’t ready by autumn, you can save it and add it to your new or existing garden in the early spring days.

There are various ways to use compost, depending on the type of garden you have, the kind of plants you want to grow, and the result you want. Here are a few common ways people use compost, tried and tested by the Fantastic gardeners.

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How to use compost for a vegetable garden

Vegetable gardens have a single essential purpose: to raise thick and juicy edible plants for the gardener. If you want to achieve that, your veggies need a lot of nitrogen. Here’s how to use compost for vegetables:

  1. Spread 10-15cm of compost on top of your current bed during autumn.
  2. Mix it into the soil in the spring by tilling it.
  3. Add a handful of compost to each planting hole you dig when you get to planting.
  4. Spread a thin layer of compost around the base of each plant after they start growing to use as mulch.
  5. For “heavy feeder” plants like melon, pumpkin, eggplant, and tomato – mulch with compost monthly to increase the quality of your produce. Every time you add fresh compost, dig the older into the soil.
Don’t overdo it by adding too much compost. Heavy feeders can handle it and grow very large, but other vegetables can’t, and you risk burning them!
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How to use compost for raised garden beds

You can spread compost and dig it into the soil for raised garden beds, but the effort is optional. It’s good enough to simply sprinkle it along the surface and let the seasonal rains carry the nutrients all the way to the roots.

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How to use compost for shrubs and trees

The best approach with shrubs and trees is to work 2-3cm of compost into the top 5-6cm of the soil beneath. With trees, you should cover the entire area from the trunk to the dripline.

You can also use it as mulch around your trees and shrubs to make them more drought-resistant and prevent weeds. Your mulch layer should be at least 3cm but no more than 10cm and shouldn’t touch your tree or shrub’s bark.

When planting trees, don’t add compost to their planting holes since this will obstruct the tree roots when they try to grow beyond the hole.

How to use compost for flowers

If you wonder how to use compost for flowers, it’s best to wait until spring to mix it into the topsoil. If you insist on adding it in the autumn, you can use compost as mulch to help your plants stay warm during the winter and retain their moisture.

How to use compost for your lawn

Compost can be implemented into the soil base before you seed your lawn for better results. Add a 7-8cm layer on top before seeding, and watch your lawn thrive. While it isn’t necessary, you can also take it a step further and till the compost to a depth of 15-20cm.

Another thing you can use it for is getting rid of bald spots on existing turf. Mix a 2-3cm layer with the top 4-5cm of soil wherever your lawn has bald spots to help it cover them.

Last but not least, you can spread a 2-3cm finely-screened compost across your entire lawn and rake it evenly to use several of its benefits at once – prevent weeds, protect from pests, cover bald spots etc.

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  • Compost can help in almost every aspect of gardening.
  • Using compost that isn’t finished is harmful.
  • The best time to add it is autumn, but early spring is also okay.
  • Using less than enough compost is almost always better than overdoing it.

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Did you enjoy the guide to using compost? Which one of its benefits is your favourite?
Let us know in the comments section below!

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