Johnson-Su composting is a method of making high-quality, biologically rich compost using a carefully designed static composting system. It is best known for producing a compost that is often described as fungal-dominant, or at least more fungal-rich than many fast, turned composting methods.
This composting method was developed by Dr David Johnson and Hui-Chun Su Johnson, whose work has focused on soil biology, carbon cycling, microbial diversity and the role of compost as a biological inoculant.
Unlike conventional hot composting, where piles are turned regularly to add oxygen and speed up decomposition, the Johnson-Su method uses a static, no-turn bioreactor. Air is supplied through vertical pipes during the early stage, then the compost is left to mature slowly over many months.
The aim is not simply to make a bulk soil amendment. It is to create a small amount of highly biologically active compost that can be used to inoculate soil, seed, compost extracts or compost teas.
In regenerative agriculture, this is especially interesting because it shifts the focus from compost as “nutrients in a heap” to compost as living biology.
And that is where Johnson-Su composting becomes rather exciting.
Johnson-Su composting is a no-turn aerobic composting method designed to encourage diverse microbial life, including fungi, bacteria, protozoa and other soil organisms.
It is usually made in a cylindrical composting unit called a Johnson-Su bioreactor.
The system is designed to:
A typical Johnson-Su bioreactor is filled with a well-mixed, moist blend of organic materials. During setup, several vertical air pipes are placed through the compost. These pipes create airflow and help maintain oxygen. After the compost has settled and begun to stabilise, the pipes are usually removed, leaving air channels behind.
The compost is then left to mature for around 9 to 12 months, sometimes longer.
This slow maturation is important. Fungal networks take time to develop. Many fast composting systems prioritise speed. Johnson-Su composting prioritises biology.
It is less “make compost quickly” and more “cultivate a microbial civilisation in a bin.” Tiny compost metropolis energy.
The method is named after Dr David Johnson and Hui-Chun Su Johnson.
Their research and practical work explored how compost biology might help improve soil health, plant growth, carbon cycling and the efficiency of photosynthesis in farming systems.
The Johnson-Su bioreactor was designed to make compost that could be biologically consistent, aerobic and relatively easy to replicate. It was developed partly in response to the challenges of conventional composting, where turning, temperature spikes, uneven moisture and anaerobic pockets can affect microbial communities.
The goal was to create a composting system that supports a rich soil food web and produces a material suitable for inoculating agricultural land with beneficial microbes.
Johnson-Su compost differs from many traditional composting methods in several important ways.
1. It Is Not Turned
Most hot composting systems rely on turning the pile to add oxygen, mix materials and control temperature.
Johnson-Su compost is not turned after the initial setup.
The idea is that turning can physically disrupt fungal hyphae and change the microbial succession inside the compost. By leaving the compost undisturbed, fungal networks have more opportunity to develop.
2. It Uses Passive Aeration
Instead of turning, the compost is aerated using vertical air channels.
At the beginning, plastic pipes or similar tubes are inserted into the composting material. These allow air to move through the pile. Later, when the pipes are removed, the holes remain as air channels.
This helps keep the system aerobic.
3. It Matures Slowly
Johnson-Su compost is usually matured for many months.
This long curing period is one of the defining features of the method.
Fast compost may be finished in weeks or a few months. Johnson-Su compost is more like a slow-aged biological inoculant. The extra time allows microbial communities to develop and stabilise.
4. It Is Often Used as an Inoculant
Many composts are spread in large amounts to add organic matter and nutrients.
Johnson-Su compost is often used in much smaller amounts because it is valued for its biology.
It may be applied as:
The idea is not necessarily to apply tonnes per hectare. It is often to introduce beneficial biology and stimulate soil life.
5. It Is Designed to Encourage Fungi
Many conventional composts, especially frequently turned hot composts, may end up more bacterial-dominant.
Johnson-Su composting is designed to encourage more fungal development by avoiding disturbance, maintaining moisture and allowing long maturation.
Fungi are important in soils because they help decompose complex organic matter, form relationships with plants, improve soil aggregation and support nutrient cycling.
The phrase “fungal-dominant compost” is often used around Johnson-Su composting, but it is worth understanding what that means.
Soils naturally contain both bacteria and fungi. Both are important. The goal is not to declare fungi the winners and bacteria the compost villains. Bacteria are doing plenty of excellent work.
However, many degraded agricultural soils are thought to have lost fungal diversity and fungal biomass through tillage, bare soil, synthetic inputs, compaction and simplified rotations.
Fungi can support soil health by:
Mycorrhizal fungi are especially important because they form partnerships with many plants, exchanging nutrients and water for plant sugars.
Johnson-Su compost is valued because it may help reintroduce or support fungal-rich microbial communities in the soil.
That said, it is best to be careful with claims. Compost biology can vary depending on ingredients, moisture, temperature, time and management. Not every homemade Johnson-Su style compost will automatically be perfectly fungal-dominant. The method creates favourable conditions, but quality still depends on execution.
A Johnson-Su bioreactor is usually a tall, cylindrical composting container.
It can be made from materials such as:
The classic design includes:
The exact design can vary, but the principles are the same:
The vertical aeration pipes are one of the most distinctive parts of the design. They are inserted during filling and later removed, leaving channels through the compost.
Johnson-Su compost can be made from a mix of organic materials.
Common ingredients include:
The exact recipe can vary, but a good mix usually includes carbon-rich and nitrogen-rich materials.
These include:
Carbon-rich materials help provide structure and food for fungi.
These include:
Nitrogen-rich materials help fuel microbial activity.
The trick is balance. Too much nitrogen can lead to smells and anaerobic conditions. Too much woody carbon can slow the process dramatically.
A mix of particle sizes is also useful. Fine materials can compact, while coarse materials help airflow.
Moisture is crucial in Johnson-Su composting.
The compost should be moist like a wrung-out sponge. Not dry and dusty, not dripping wet.
If it is too dry, microbial activity slows down and fungi struggle to grow.
If it is too wet, oxygen is pushed out and the compost may become anaerobic. That can lead to bad smells and poor-quality compost.
Good moisture management means:
In dry weather, the bioreactor may need watering. In wet climates, it may need a cover to prevent saturation.
Moisture is one of those boring details that quietly decides whether the whole thing works. Compost is humbling like that.
Johnson-Su composting can go through a warm phase, especially early on, but it is not managed in the same way as conventional hot compost.
Traditional hot composting often aims for high temperatures to kill weed seeds and pathogens. Johnson-Su composting tends to focus more on stable aerobic decomposition and biological maturation.
The temperature should not become so high that beneficial biology is damaged or the pile dries out too quickly.
If the compost gets very hot, it may indicate too much nitrogen or too much easily decomposable material.
If it does not heat at all, it may be too dry, too low in nitrogen, too cold or poorly mixed.
Because Johnson-Su compost is often used as a biological inoculant rather than a bulk compost, ingredient selection matters. Avoid adding diseased material, persistent weeds or contaminated inputs unless you are confident the composting process will handle them safely.
Step 1: Choose a suitable site
Place the bioreactor somewhere accessible, level and protected.
A good location should have:
Avoid placing it where runoff could cause pollution.
Step 2: Build the bioreactor
Create a cylindrical or square structure using mesh, posts and breathable fabric.
The sides should hold the compost in place while allowing airflow.
Make sure the base drains freely but does not allow material to fall out easily.
Step 3: Prepare aeration pipes
Use several vertical pipes with holes drilled into them. These will create air channels.
Place them evenly through the composting area before or during filling.
They should be tall enough to reach through the full depth of the compost.
Step 4: Prepare your compost materials
Mix your ingredients before filling.
Aim for a balanced mixture of:
Chop or shred large material where possible. This helps create a more even composting process.
Step 5: Wet the materials thoroughly
Moisten everything as you build the pile.
It is much easier to wet the material during filling than to rehydrate a dry bioreactor later.
The finished mix should feel like a wrung-out sponge.
Step 6: Fill the bioreactor evenly
Add material in layers, gently packing around the aeration pipes.
Do not compact it too heavily. The compost needs pore spaces for air and biology.
Keep the mix consistent throughout the reactor.
Step 7: Cover the top
Cover the top with breathable material, straw, hessian, old carpet, cardboard or a loose lid to protect from drying and heavy rain.
Do not seal it airtight.
Step 8: Monitor moisture and smell
During the first few weeks, check regularly.
A healthy bioreactor should smell earthy, sweet or pleasantly compost-like.
Bad smells may indicate anaerobic conditions. If it smells rotten, sour or like sewage, something has gone wrong with moisture, airflow or ingredients.
Step 9: Remove the aeration pipes
After the compost has settled and begun to stabilise, the pipes are usually removed, leaving vertical air channels.
Do this carefully so the channels remain open.
Step 10: Let it mature
Leave the compost undisturbed for many months.
This is the patience phase. Not glamorous. Very important.
During this time, keep moisture consistent and protect the compost from drying out or becoming waterlogged.
Step 11: Harvest the compost
After around 9 to 12 months, the compost should be dark, crumbly, earthy-smelling and biologically mature.
It may contain visible fungal strands, depending on conditions and ingredients.
Harvest gently to preserve structure and biology.
Because Johnson-Su compost is often valued as a biological inoculant, it is commonly used in small amounts.
A compost extract is made by mixing compost with water to extract microbes.
Unlike aerated compost tea, a simple extract is usually used soon after mixing and is not necessarily brewed for long periods.
It can be applied to:
Small amounts of compost extract or fine compost may be used to coat seeds before sowing.
The goal is to introduce beneficial microbes close to the emerging roots.
Seedlings or young plants can be dipped in a compost extract before planting.
This may help introduce microbial life around the root zone.
Johnson-Su compost can be applied directly to soil in small quantities, especially around plants, in planting holes or as part of a compost blend.
Some people use Johnson-Su compost to make aerated compost teas.
This requires care, clean equipment and good water quality. Poorly made compost tea can become anaerobic or inconsistent.
A small amount of mature Johnson-Su compost can be added to new compost systems as a biological starter.
Encourages fungal growth: The no-turn method and long maturation period can support fungal development.
Low labour after setup: Once the bioreactor is built and filled, it requires less physical turning than conventional compost.
Produces biologically rich compost: The method aims to produce compost with diverse microbial life.
Reduces disturbance: No-turn composting protects developing fungal networks.
Can be made on farms or smallholdings: The system can be built with relatively simple materials.
Useful as an inoculant: Small amounts can be used to support soil biology, seed germination and plant roots.
Supports regenerative farming goals: It aligns with soil health, biology, carbon cycling and reduced input dependence.
It takes time: This is not a fast composting method. Expect many months before it is ready.
Moisture can be tricky: Too dry, and the process stalls. Too wet, and it may become anaerobic.
Ingredient quality matters: Contaminated inputs can lead to poor compost. Avoid materials with persistent herbicides, pollutants, plastics or chemical residues.
It may not kill weed seeds: Because the system is not managed primarily as a hot compost, weed seed destruction may be less reliable.
It produces limited volume: Johnson-Su compost is usually made for biological quality rather than bulk quantity.
Results vary: Biology depends on materials, climate, management and maturity. Not every batch will be equally good.
Testing can be difficult: Assessing compost microbiology requires microscopy or lab testing if you want detailed data.
| Johnson-Su Composting | Hot Composting |
|---|---|
| No-turn system | Usually turned regularly |
| Long maturation period | Faster process |
| Passive aeration | Oxygen added through turning |
| Encourages fungal development | Often more bacterial-dominant |
| Used as biological inoculant | Often used as bulk compost |
| Lower labour after setup | More active management |
| May not reliably kill weed seeds | Can kill weed seeds if hot enough |
| Takes 9 to 12 months or more | May finish in weeks or months |
Both methods are useful. They simply have different goals.
Hot composting is excellent for processing larger volumes of organic material quickly. Johnson-Su composting is better suited when the aim is high-quality microbial inoculation.
A farm may use both: hot compost for bulk organic matter and Johnson-Su compost for biology.
Johnson-Su composting fits naturally into regenerative agriculture because it focuses on soil biology.
Regenerative farming aims to:
Johnson-Su compost can support this by providing a biologically rich amendment that may help reintroduce beneficial organisms to degraded soils.
However, compost alone is not enough.
If soil is repeatedly tilled, left bare, compacted or treated harshly, introduced microbes may not thrive. Biology needs habitat.
To make the most of Johnson-Su compost, combine it with:
Think of Johnson-Su compost as an inoculant. The farm still needs to provide food and shelter for the biology.
You would not release a herd of tiny microbes into a desert and expect them to build a village without snacks.
Johnson-Su composting is worth considering if you are interested in soil biology and have patience.
It may be especially useful for:
It may be less suitable if you need large volumes of compost quickly, want to kill weed seeds reliably, or do not have time to manage moisture.
For many growers, the best approach is to try one bioreactor as a small experiment. Use the compost on a trial area and observe results.
Measure what you can:
Regeneration is best approached with curiosity rather than blind faith.
The more stable and biologically friendly the environment, the better your compost is likely to be.
How long does Johnson-Su compost take? Usually around 9 to 12 months, though some people mature it for longer.
Does Johnson-Su compost smell? It should smell earthy and pleasant. Bad smells suggest anaerobic conditions.
Do you turn Johnson-Su compost? No. The method is designed to be a no-turn composting system.
Can I use Johnson-Su compost like normal compost? Yes, but it is often used in smaller amounts as a biological inoculant rather than a bulk amendment.
Does it kill weed seeds? Not reliably in the same way as well-managed hot compost. Avoid adding seeding weeds if this is a concern.
Can I make it on a small scale? Yes. Smaller systems are possible, though they may be harder to keep stable. Good moisture and airflow still matter.
Is it suitable for farms? Yes. It is especially useful for farms interested in soil biology, compost extracts and regenerative practices.
Johnson-Su composting is a slow, no-turn composting method designed to produce biologically rich, fungal-friendly compost.
It is different from conventional hot composting because it focuses less on speed and more on microbial diversity, fungal development and long-term maturation.
For regenerative farming, this makes it especially valuable. It encourages us to think of compost not just as decomposed organic matter, but as a living inoculant that can help rebuild soil biology.
But Johnson-Su compost is not magic. It works best as part of a wider soil health approach that includes living roots, soil cover, reduced disturbance, diversity, organic matter and good water management.
Make the compost. Feed the soil. Protect the habitat. Let the biology do what biology does best.
Quietly, slowly and with absolutely no interest in your preferred deadline.
