Biochar vs Compost vs Fertiliser: What's the Difference?
Biochar, compost, and fertiliser all get added to soil, so it is easy to mix them up. They are not the same thing and they do different jobs. Here is the simple version.
The Short Answer
- Fertiliser feeds the plant
- Compost feeds the soil
- Biochar helps the soil hold onto water and nutrients for the long term
What Is Fertiliser?
Fertiliser is concentrated nutrients, such as nitrogen, phosphorus, and potassium, that plants need to grow. It works quickly. You apply it, and the plant can use it fairly soon after.
Good for: a fast boost to plant growth.
Limit: it does not improve the soil itself. Nutrients can also wash out of the soil if there is nothing there to hold them.
What Is Compost?
Compost is broken down organic matter, such as food scraps, garden waste, and manure. It adds nutrients and organic material to the soil and feeds the microbes that live in it.
Good for: improving soil structure and adding organic matter.
Limit: compost keeps breaking down. Over time it is used up and needs to be topped up regularly.
What Is Biochar?
Biochar is a charcoal-like material made by heating wood or other plant material with very little oxygen, a process called pyrolysis. It is mostly carbon, and it is full of tiny holes.
Those holes give it a very large surface area. In soil, that surface can hold water and nutrients and give microbes somewhere to live.
Good for: long-term soil improvement. Biochar breaks down very slowly, so it stays in the soil for a long time.
Limit: on its own, biochar is not a fertiliser. It does not add much in the way of nutrients unless it has been charged first (see below).
Side-by-Side Comparison
| Attribute | Fertiliser | Compost | Biochar |
|---|---|---|---|
| What it does | Feeds the plant | Feeds the soil | Improves soil long term |
| Speed | Fast | Medium | Slow |
| How long it lasts | Short | Medium | Very long |
| Holds water and nutrients | No | Some | Yes |
| Adds nutrients | Yes, lots | Yes, some | Very little on its own |
Do You Have to Pick One?
No. They work well together. In fact, biochar is often mixed with compost or fertiliser before it goes on the ground. This is called "charging" the biochar. Fresh biochar can soak up nutrients from the soil, so mixing it with compost or fertiliser first means it holds nutrients and releases them to plants instead of taking them.
A common approach
- 1.Mix biochar with compost or a nutrient source
- 2.Let it sit for a while so it can soak up nutrients
- 3.Apply it to the soil
Which One Should You Use?
- Need quick plant growth? Fertiliser
- Need to improve poor or tired soil? Compost
- Sandy soil that drains too fast, or want a long-lasting improvement? Biochar, ideally mixed with compost
- Want the best all-round result? A combination
Every soil is different, so a soil test is the best way to know what yours actually needs.
Biochar from Ignis
Ignis makes biochar from Victorian waste timber. If you are a farmer, grower, or landscaper and want to know more about using biochar, get in touch.
Get in Touch