To put old compost in a compost bin mix it with new compost, dry fall leaves, fruit and vegetable scraps and water it in. Old compost can make up to 50% of the new compost mix in your compost bin. Supercharge old compost by adding worm castings, pelleted chicken manure and aged cow manure. In 3-6 months you will have supercharged compost for your garden.
What to do with old compost
There are many ways to use old compost in your garden that will benefit your garden and plants. Old compost is a good source of organic matter and micronutrients so adding it to garden beds, top dressing plants and mixing it through new compost are all great ideas.
Use old compost to top dress garden beds
If the levels of your garden beds are starting to drop, you can sprinkle old compost on the top of the soil to bring the level back up. Move back any mulch first and then add the old compost on top of the soil.
Rake and cover it with the mulch. If you are using the old compost around existing plants, make sure you don’t dig the compost in and disturb the roots. This is important for fruit trees who have delicate feeder roots near the surface of the soil.
Add old compost to the top of worm farms
If you have a worm farm, you can add a small amount of old compost to add to the top of your worm farm. Old compost can be used to cover vegetable scraps in your worm farm that may be attracting ants or flies.
Keep a bucket of old compost next to your worm farm and scoop out small amounts when you need. The worms will incorporate the old compost through the worm farm, enriching it and turning it into worm castings that can be put back on your garden.
Add old compost to garden beds
You can add old compost to your garden beds if you need to top up the level. A simple way to do this is to put the old compost in a wheelbarrow, add 1-2 handfuls of pelleted chicken manure and some aged cow manure. Mix it through using a fork or spade and add it to vegetable garden beds or flower beds.
You can use this old compost mix to top up soil after removing old, spent flowers like I just did with my canna lilies. These have been planted in the same spot for over 5 years so are ready to be lifted and the soil improved. Use old compost boosted with animal manures to add nutrient rich organic matter to your garden.
Does compost go bad?
Old compost can become dry and lack microorganisms if it has been left for more than a year. Once all of the organic matter has been broken down the substance turns to humus and the microorganisms and worms will move on to feed on something else. There are simple ways to revive old compost and make it a fantastic addition to your garden.
How to revive old compost
To revive old compost add some extra nutrients and water if it has dried out. If compost is left in a compost bin for too long without attention it can dry out. Black lidded compost bins can heat and dry out the compost once it has fully broken down so here are some steps to revive it.
Add water to your old compost
The first step to reviving old compost is to add water. If it looks dry then use a sprayer nozzle to wet it down. This will stop any particles flying in the air and start to encourage microorganism to return. Add water until it looks like damp potting soil but don’t soak it. You can let it dry out slightly before using.
Add pelleted chicken manure to your old compost
Add 1 handful of pelleted chicken manure to every bucket sized amount of compost. Adding pelleted chicken manure will help the compost to begin to hold water and add back nitrogen. This will create a supercharged mix which will attract more microorganisms and provide a slow release fertilizer for your plants.
Add aged cow manure to your old compost
To supercharge your compost mix, add aged cow manure up to ¼ of the mix. Aged cow manure is a mild fertilizer which will help to revive your compost. Mix it through using a fork and this will create a fantastic mix to use to top dress around fruit trees, top up raised vegetable beds or use a potting mix.
What to do with old compost in the bottom of containers
Use leftover compost in the bottom of containers or pots to add back to your new compost or add to the top of your worm farm.
Putting old compost in the green bin
Most councils state that “soil” cannot be added to your green waste bin. Because compost is essentially soil, large amounts should not be added to your green waste bin. Most local councils will turn green bin waste into compost in large composting facilities.
In Australia, all local councils will have different rules about whether you can add compost to your green bin so send an email to their customer service team just be sure.
How to use last years old compost
You can use last years’ compost in your garden but there are a few things to check first.
Is the compost dry?
If the compost is dry and crumbly or has a white powder you will need to wet the compost off. This is important to do before you handle the compost so that small particles do not get in the air.
Does the compost have worms?
If the compost contains worms, then it is likely that it still full of organic goodness. Worms will live in healthy compost and eat the bacteria and fungi that are breaking down the organic matter. Finding worms in your old compost is a sign that your compost is good to use on your garden.
Is the old compost completely broken down?
While we might assume that old compost is completely broken down it can still contain large pieces of mulch, food scraps or leaf matter. If the compost mix wasn’t correct to begin with, the food scraps, leaves and bark may not break down at all.
To fix the old compost, turn it over with a garden fork and see if it has broken down. If not, mix through a handful of pelleted chicken manure and worm juice if you have it. This will supercharge bacteria growth and get the compost to finish breaking down. Turn it regularly and within 2-3 months it should be fully broken down and ready to use on your garden.
How to put old compost in a vegetable garden
Put old compost in your vegetable garden before you plant a new season crop. old compost is good for root vegetables like carrots, turnips and swedes which do not need soil that is rich in nutrients. They prefer to be planted in soil that has had a previous crop so using old compost will be perfect for them.
Old compost can be used to grow other vegetables but first add pelleted chicken manure and aged cow manure. This will ensure that your vegetables will have long-lasting nutrients. This is great for tomatoes, strawberries, cucumbers, peppers and aubergene.
How to put old compost in a worm farm
You can put old compost in your worm farm to top up the level, use as worm bedding or sprinkled on top of food scraps to keep flies away. Old compost is perfect for worm farms as it provides a good bedding and if it hasn’t completely broken down, the worms will work to finish the process. Afterwards you will have a moisture rich ‘vermicompost’ ready to add back to your garden.
Using old compost as mulch
You can use old compost as mulch underneath fruit trees, shrubs, annual flowers or large trees. I prefer to add another layer of bark chips or sugar cane on top of the compost as it will help to retain the moisture well.
For more on composting check out this article.
I am an accredited practicing dietitian, experienced gardener and a dedicated cook. I love writing and sharing my experience so you can learn from my successes and mistakes.