Among circles of gardeners, the terms “humus” and “compost” gets used interchangeably. While both humus and compost are essential to a healthy land, they are different in many ways.
But, do not think that compost and humus are applied to totally different situations. They are common parts in both man-made gardens and natural greeneries.
It is important you know the difference between humus and compost if you are getting serious with your gardening.
If you want a soil that will provide nutrition to all types of plants over the different seasons, read this guide and you will certainly be a better gardener after.
Table of Contents
What is compost?
Compost is a group of organic matter that is already decomposing. The definition is not strict to the amount of soil, amount of organic waste, or how is it stored.
As long as it is rotting on soil, it is considered to be compost.
You can usually find compost bins in houses. They look like an open container with a bed of soil topped with organic waste from the house. This waste could be leftover food, fruit peels, or even paper.
It is hard to know whether it has finished composting. A good rule is if the waste you have thrown there are “not there” anymore, it means it has already decayed with the soil.
Finished compost is usually used in businesses that involve keeping plants and trees healthy. Some good examples are nurseries, hotels, and resorts.
However, a lot of homeowners now are making their own compost bins for their plants.
What is a humus soil?
Humus can be defined as naturally-formed compost. This could be rotting twigs under the water in swamplands or pile of leaves buried in the soil in forests.
They are found everywhere compared to compost since humus is always produced by the natural processes in any ecosystem.
However, there is a lot of confusion whether humus is just finished compost or humus is a natural compost (no humans involved). Let us find out how these two decaying matter are different and similar to each other.
humus vs compost What is the difference?
The difference in compost and humus is a contentious one which is why up until now the topic is still being debated.
Basically, any soil has humus since the soil which you got from your yard has been in the decomposition cycle for hundreds of years. So, the soil you use in your compost has humus.
Here are some ways how compost and humus are different to each other.
- Level of decay. Compost is traditionally any organic matter that is rotting. However, it has been attached to a different definition to separate it from humus. Basically, compost is any pile that is still decaying. When a compost has become “stable,” it is now considered as humus. To sum it up, when a leaf is still decaying, it is a compost. When you cannot leaf has “blended” into the soil, it is now humus.
- Appearance and texture. Compost is, well, soil that has rotting banana peel or scrap meat. It is heterogenous that you can distinguish which materials are which. Humus looks darker and feels more like a wet sponge compared to the topsoil which has a brown color and a grainy texture. The reason for this is humus has almost zero exposure to human and animals when untouched. The decomposition process is uninterrupted.
- Human involvement. Part of the reason why the term “compost” is used more often among gardeners is that compost has human involvement in its decomposition compared to humus which has none (direct, a least).Compost bins are continually fed with organic waste from human households. The formation of humus are often unseen. Think of the pile of leaves at the nearby park. Park rangers do not assemble these pile of leaves every day. It just forms there and the next time you visit you will notice that it is gone and fresher leaves have replaced it.
- Method of decay. When we want to understand how different compost and humus are in how both decays, we need to understand the human involvement for both which we discussed in the previous entry. The reason for this is compost decays with oxygen presence. This is known as the aerobic decomposition. This is possible because man-made bins have aeration holes or just plainly open. Meanwhile, humus is usually made via anaerobic decomposition or decaying without (or minimal) oxygen.
- Nutrient content. Humus has higher levels of NPK or Nitrogen, Potassium, and Magnesium since the organic matter have completely decayed. However, since anaerobic process is like fermentation, humus has more carbon and methane.
Here is a handy list of the macro-nutrients and micronutrients (items g to j) found in soil.
- Nitrogen. It is helpful in the vigorous growth of plants especially to spreading plants.
- Potassium. Aids in the reproductive function of plants.
- Magnesium. Helps in keeping the plant looking green and healthy.
- Calcium. Important in having a permeable wall which nutrients come in.
- Phosphorous. Necessary in root and seed growth.
- Sulfur. Maintains a healthy metabolism.
- Iron. Also helps in chlorophyll-related functions like oxidation.
- Manganese. Essential in photosynthesis, nitrogen metabolism, and respiration.
- Zinc. Responsible for synthesizing proteins.
- Copper. Activates enzymes for photosynthesis and respiration.
To put it side-by-side, compost is any decaying matter. Whether it is a dead bird or a leftover apple, it is compost.
It becomes humus when it has completely decayed, its nutrients absorbed by the soil, and becomes part of the soil.
You can say that everything is a compost first then a humus, but not the other way around.
When & Why to use Compost to Your Garden
Compost is used to have an eco-friendly way of disposing organic waste. Instead of putting it in a plastic bag and throwing it along with other non-biodegradable waste, you can just simply throw it to any land near you (as long as you do this in a tidy manner).
Also, it is a way of keeping any organic waste from being thrown in the drain and entering the wastewater system.
Once the organic waste reaches a river or lake, it can cause the growth of algae which takes up the oxygen for the fish.
You should also use your compost when planting or transplanting seedlings. The seedling will have a healthy soil to start growing since the first few weeks (especially after being transplanter to the soil from a pot) are vital in the survival of the seedling.
What are the benefits of humus compost to the soil?
Humus is naturally richer in nutrients due to its longer duration of decomposition. Humus is a good way to start your compost.
You can find the humus when you dig deep enough to reach a moist and spongy layer of soil. Usually, once you see earthworms, it is the humus layer already.
Mixing it with compost will make the decomposition process faster. Make sure you include some worms in your compost bin.
Humus is a more preferable choice when it comes to enriching semi-adult or even fully adult trees. This is because as trees grow, they require more nutrients to live.
When a tree is fully grown, the leaves will naturally fall down, become compost when decaying, then become humus when fully decayed.
How to keep your soil and plants healthy
While most gardeners encourage to add the latest batch of fertilizer from the local market or establish a strict watering schedule, the most effective way of keeping your garden healthy is letting it be.
This does not mean that you will have zero attendance towards your garden. What this means is you do not need to keep adding store-bought garden supplements or gadgets to have a healthy garden.
Your goal is to help plants have a healthy growth by themselves and not tamper with it. Plants have been growing, dying, and reproducing since the start of time so they know how to adapt and survive in natural conditions.
This is the reason why tropical rainforests are lush and dense compared to nearby forests in urban areas.
For the sake of the argument (how to keep your garden healthy), one unobtrusive way of doing this is have a compost bin and keep your garden from your rowdy pets and from being walked on.
Not knowing the difference between compost and humus is going to make you a bad gardener. A lot of gardens have thrived well even if its owner is not an expert on the technical know-how of compost and humus.
However, knowing the difference is an advantage. You should know how the soil interacts with organic matter and how is it beneficial to your plants (and to the soil itself).
Plants are self-maintaining but delicate beings. While they are best to have a minimal routine with it, they are also vulnerable to dying caused by bad practices.
At the end of the day, some of us do not want to be a good gardener, but a great one instead.
Last Updated on June 23, 2021 by Lindsey Hyland
Lindsey Hyland grew up in Arizona where she studied at the University of Arizona’s Controlled Environment Agriculture Center. She continued her gardening education by working on organic farms in both rural and urban settings. She started UrbanOrganicYield.com to share gardening tips and tactics. She’s happy to talk about succulents and houseplants or vegetables and herbs – or just about anything in a backyard garden or hydroponics garden.