Barnes Common frequently receives enquires from people who want to make their gardens more sustainable, and here, we respond to some of these queries. If you have a question you would like us to feature – whether related to food growing or sustainable gardening in general – please contact Nicky. If you have tried these ideas at home, let us know how it goes!
At the growing project, we often receive queries about composting. It is a key tenet of gardening sustainably, but there is a huge amount of confusing and often contradictory information out there – it can be hard to know where to start! This month, we will explore the basics of composting and dive into some troubleshooting.
Composting is the process of recycling organic matter into valuable fertiliser which can be used in the garden. In order for compost to be effective, 4 components must be present; green materials, brown materials, water and oxygen. Green materials are high in nitrogen, and are soft and leafy – for example, soft plant matter, or vegetable waste. Brown materials are high in carbon and are harder and woodier – things like twigs, or shredded cardboard.
Both carbon and nitrogen must be present in order for composting to be successful. There is a lot of research into the exact carbon:nitrogen ratio that works best – if you’re interested in the science of this, there are a huge amount of resources out there. However, for the purposes of home composting, it is enough to aim for a ratio of roughly 50:50. This will create the right structure, level of moisture and aeration.
The right balance of water is needed in a compost heap. If it becomes too wet, anaerobic conditions are created, which slow decomposition. If it is too dry, decomposition will not occur. In especially hot, dry weather, you may need to add more wet material, or even water your compost heap, to ensure the materials continue to break down.
If the balance between green and brown materials and the water level is right, the compost heap will naturally have the right amount of oxygen. Some people turn the heap to aerate it, and prevent the formation of anaerobic pockets. This is useful, and can speed up the process of decomposition. However, it is not essential.
If you are running into problems with your compost heap, it is likely to be because these four elements are out of balance in some way. Below, we address some commonly raised queries.
My compost isn’t breaking down – why not?
One of the 4 components (green, brown, water, oxygen) is missing, or the components are out of balance. You’ll need to establish which element this is in order to rectify the situation.
My compost heap stinks – why is this?
This is likely to be due to too little aeration, or too much nitrogen. Turn the heap to introduce oxygen, or add more brown material if the heap seems wet or sludgy.
Why should I compost, instead of just adding un-decomposed organic matter to the garden?
Compost feeds the soil in a slow and steady manner, allowing plants to access the nutrients they need. A compost heap speeds up natural decomposition. Undecomposed matter provides an un-even feed, can result in habitat for slugs, and may be spread around by foxes.
Can I compost perennial weeds?
Perennial weeds add valuable nutrients to the compost heap. They won’t re-grow if they’re not exposed to light, so add them to the heap and mix them in.
What about annual weeds?
If you add the seed heads of annual weeds to the compost heap, it is possible they will germinate the following year when you spread compost on the garden. It is fine to add the rest of the plant to the compost heap though; as with perennial weeds, they will add valuable nutrients the mix.
Can I compost blighted tomatoes?
Yes – blight only survives on living plant material. Charles Dowding has done an experiment where he mulched tomato plants with compost containing previously blighted material, with no negative effects.
Can I compost citrus peel?
Many people avoid composting citrus peel on the basis that it will increase acidity in the soil, but this is a gardening myth. The acidity quickly dissipates as the peel breaks down in the compost. As with everything, as long as you have a good balance of other materials, it is fine to add citrus peel to your compost heap.
Do you have any compost troubleshooting queries of your own? Contact Nicky to have them featured in the next growing project newsletter.
Previous blogs:
How Can I Garden Without a Garden?
What is permaculture, and how can I apply it in my own garden?
How to Plant a Pollinator-Friendly Garden