The difference between compost and humus is one of the most debatable and probably confusing topics among home gardeners. Although the terms ‘compost’ and ‘humus’ are often used interchangeably, the truth of the matter is, they aren’t similar.
When the organic material has completely decomposed, it is identified as humus. Whereas compost is a term that refers to an active phase of decomposition where the decaying plant matter tends to be most beneficial to the soil. In other words, humus is a mature and stable form of compost.
However, there is more to it. You may have heard about gardening centers selling ‘humus compost,’ so what about it? If you are interested in diving deep into the difference between compost and humus, including the benefits and key elements, this article is for you.
Difference between Humus and Compost
Compost is the black dirt produced from decomposing organic material such as food scraps and plants. Usually, compost is considered a ‘finished product’ when individual contributors are no longer distinguishable.
Even though organic materials in compost cannot be identified as they are turned into dirt, it doesn’t mean the decomposition process has completed or reached the end state.
Compost refers to a phase where microscopic activities of breaking down and decaying the organic material are still going on.
Humus, a dark, mostly carbon-based spongy substance, is the end product obtained from the complete decomposition of the organic material. The ready-to-use compost we put in our gardens contains a small percentage of humus.
The bottom line is: humus isn’t compost, but the components of the compost, when decomposed fully, become humus.
Organic Material Vs. Organic Matter
Organic material can be anything from a dead animal to plant matter that was once alive and now is in or on the soil, actively decomposing. However, traditional compost doesn’t contain animal products but waste food, leaves, lawn clippings, cornstalks, green manures, sludge, etc.
For the organic material to convert into organic matter, it must be decomposed into humus. Microbes present in the soil break down the organic substances to a molecular level, gradually releasing the nutrients into the ground for plants to uptake.
By the time organic material converts into the final, stable organic matter or humus after a complete decomposition, it’s already been depleted of the essential chemicals by microorganisms.
This is why organic matter is inert in nature and doesn’t affect the soil’s chemical properties.
What Is Humus Made of & Why It’s Important?
If you have read the above sections carefully, you should already know what humus is made of. To recap, humus is the leftover produced after a complete decomposition of the organic material. It’s essentially the inert core of the original tissue.
Humus has a crumbly and fibrous texture, enabling it to hold up to 80% of its weight in water. The loose nature of the humus soil allows air and water to flow easily through and reach the plant’s roots without meeting any resistance.
The primary function of humus is to act as a reservoir for nutrients, help increase the soil’s moisture-holding capacity and improve soil structure, fertility, and friability. As a key nutrient, humus is rich in Nitrogen.
Humus or Compost: Which is better?
Both compost and humus are beneficial amendments for increasing soil fertility and improving texture and overall plant life.
Adding compost to your garden will provide a nutritional boost and nutritional diversity to the soil. In comparison, humus is particularly helpful in preventing nutrient leaching and providing better water drainage/retention to the soil.
Besides, humus is also great for adding fungal activity to suppress plant diseases and fight nasty pathogens.
To conclude, neither humus nor compost is better than the other. Combining both will create better results.
What is Humus Compost?
We have already discussed humus and compost separately, but what the heck is ‘humus compost’?
Humus compost is “humus-rich compost.” It is a more stable and mature form of compost soil naturally rich in rotted organic matter.
Due to the beneficial characteristics of humus and compost, gardeners were adamant about adding both organic soil amendments, and that is how the ‘humus compost’ came into existence.
Manufacturers claim that commercially made humus compost is produced using higher composting standards. It’s primarily a manipulation of the decomposition rate of the organic material to increase the humus content.
Humus compost is undoubtedly a higher-quality soil amendment. This may come to you as a surprise, but most products (of course not all) sold in the name of humus are a form of compost containing a certain amount of humus. Pure humus is quite expensive.
Do you know humus originally refers to the natural decay of plants, trees, animals, and other organisms like fungi in the forest soil’s top layer? It has no human involvement and is created all by itself in nature as opposed to the commercially made humus.
How to Make Humus At Home
If you want to build your humus soil at home, below is how to do it:
Making Humus From Leaves
For this method, we will use leaves as a primary organic substance to make humus.
Step 1: Collect leaves
Gather as many as leaves from your lawn. If you don’t have trees, ask neighbors if you can gather leaves from their property.
Preferably avoid leaves from beech, oak, holly, and sweet chestnut trees as they are low in nitrogen and calcium. Leaves from black walnut and eucalyptus must be avoided for making humus because they contain natural herbicides.
Step 2: Shred the leaves
Dump all the collected leaves into a shredder. Shredded leaves typically take 2 to 4 weeks to convert into compost, whereas whole leaves can take 6 to 12 months to decay.
Check out this LWorx WG43 highest-rated electric leaf mulcher/shredder on amazon.
Step 3: Transfer shredded leaves into a container
Transfer the leaves into a larger, ideally tall mesh/wire composting container. It provides better airflow and helps microorganisms break down the leaves into compost much faster.
Place the container anywhere on your lawn where the wind is not too strong, or cover it with a plastic tarp to prevent the leaves from blowing away.
Step 4: Turn the leaves every 3 to 7 day
The simple act of turning the leaves is significant for increasing airflow inside the leaf pile, thus speeding up the decomposition process. Using a square shovel turn the leaves upside down, bringing the bottom content up to the side of the pile.
Depending on your environment, you may have to repeat the process quite often. For instance, if you have hot or humid weather conditions, turn leaves every 3 to 5 days. For cold environments, turning the leaves every 4 to 6 weeks will be more than enough.
Step 5: Add nitrogen-rich organic materials
Although optional, incorporating manure, grass clippings, food waste, or fertilizer with the compost will increase its nitrogen compound, thus helping the leaves decay faster.
You can use commercially available organic chicken, horse, cow, or rabbit manure as they are high in nutrients and greatly benefits the soil.
Ideally, mix 1 part manure, food waste, or 10-10-10 fertilizer for 4 parts of leaves for optimal results.
Step 6: Sit back and wait
The waiting period is probably the most crucial part of making humus. The organic material first breaks down into compost, and as time passes, it eventually decomposes into humus.
After the shredded leaves turn into compost (usually after 3-5 weeks), it may take a few months or sometimes a year (or more) to break down into humus.
You have to be consistent with turning the leaves during the decaying process. Also, if you notice the pile getting dry or flaky, spray some water on it. But ensure you aren’t excessively wetting the leaves; running a garden hose for 5 seconds will be enough.
Making Humus From Food and Compostable Scraps
Another best way to make humus is using kitchen scraps. Here is how to do it:
Step 1: Find an area to compost
Food when rots, it causes a bad smell. So to not be disgusted by the rotting smell or get any complaints from your neighbor, find a place in your garden suitable for composting purposes.
Alternatively, you can buy a compost tumbler or spinner from any gardening supply or home hardware store.
Step 2: Add 3-inches of carbon-rich material
Building up the pile, the first layer will include leaves, straw, hay, twigs, wood chips, small cardboard strips, or shredded paper. It will introduce the necessary carbon into the pile to help microbes break down and decay the material.
Step 3: Add compostable materials
Collect all food scraps from your kitchen and put them over the pile. When adding compostable material, you have to be cautious to avoid anything that may attract pests, add toxic chemicals/heavy metals or degrade the humus quality.
Compostable waste to add:
- Food items: fruits, vegetables, eggshells, nut shells (except walnuts), coffee grounds, old herbs, and spices.
- Kitchen scraps: coffee filters, tea bags, shredded newspaper, cardboard, paper, cotton balls (100% cotton), hair, and fur.
- Natural materials: sawdust, wood chips, houseplants, grass clippings, yard trimmings, leaves, hay, and straw.
The non-compostable waste you must avoid:
- Dairy products: milk, butter, sour cream, yogurt, eggs (the yolk and whites).
- Fats: oils, grease, lard.
- Baked goods and grains: cake, cookies, pasta, rice.
- Meat products: all types of meat and fish (including the bones).
- Pet waste: feces, cat litter.
- Anything with pesticides: grass trimmings, tree trimmings, houseplants treated with pesticides.
- Items with plastic or dyes: cigarette butts, glossy magazines, colored paper, markers, leather goods, coated coffee cups, coated milk or juice cartons.
Step 4: Add another 3-inches of mulch
Food waste is naturally high in nitrogen, so to maintain a balance, add another layer of carbon-rich materials such as wood chips, straw, hay, grass clippings, or leaves.
To provide proper airflow inside the pile, add 3-4 inches of mulch after every 8-inch layer of compostable scraps.
Step 5: Turn the pile every three days
As you know, turning the composting content regularly helps in faster decomposition. Doing it every 3 to 4 days will prevent overheating alongside keeping the stink to the minimum.
However, don’t overdo it. Turning the material more frequently will disturb the fungi and other microbes colonies building up in a pile. Occasionally pour some water over the pile to maintain the required moisture.
Step 6: Wait and let it rot
You have done pretty much everything on your part. Now, you can wait for the organic material to decay and eventually convert into humus.
Depending on the various items in your composting pile, it may take anywhere between 12 to 18 months to produce humus.
NOTE: Compost when left to rot until it cannot decay any further; the end product you receive is humus. It takes years for compost to convert into humus. So understandably, more time given to decomposition will yield more humus.
Following the time period mentioned above (which is very little), you will not get 100% pure humus. However, it can certainly be considered high-quality compost with a good amount of humus content.
Frequently Asked Questions
Q. Is humus the same as compost?
While humus isn’t the same as compost, the organic material that has turned into compost will eventually become humus (albeit very, very slowly) upon decomposing completely.
Q. Does compost contain humus?
Aged compost usually has a good amount of humus in it.
Q. What compost is rich in humus?
Commercial products labeled ‘humus compost’ are probably the best options for humus-rich compost. It’s the matured, well-rotted compost soil that contains a high amount of humus content.
Q. Is humus necessary for the soil?
Humus is not necessary, but it is probably the best soil amendment you can use if you are trying to improve your soil fertility.
Humus increases the water holding capacity of the soil, improves soil structure, prevention nutrient leaching and erosion, causes soil aggregation, and maintains the nutrient cycling process.
Q. Can I use humus instead of compost?
Humus and compost both provide different benefits. Switching one over another (randomly) may do the job for you, but it won’t be optimal.
If you are still with us, we hope by now you have learned the key difference between compost and humus. Both are highly beneficial soil amendments and can be used in different conditions under specific requirements.