Do you want a bigger yield and higher quality buds from your plants?
Of course! Who wouldn’t?
It’s no secret that the better your soil is, the better your plants grow.
But do you know how to get the best soil?
Follow this organic super soil recipe and you will learn how to make the best soil for cannabis.
Seriously, you will be shocked by how well this 8 step recipe works.
It’s fun, easy, inexpensive, and I am here for you every step of the way.
The organic super soil recipe that will blow your mind
This super soil recipe uses principles of soil science to create a living organic soil that is perfect for growing outstanding cannabis plants.
The ingredient list
Here is the ingredient list for those of you who want the quick and dirty details.
- Base Materials
- Compost: 15% of total volume
- Worm Castings: 15% of total volume
- Peat: 30% of total volume
- Scoria: 30% of total volume
- Biochar: 10% of total volume
- Nutrients and Minerals
- Crustacean Meal: ½ cup per 1 cubic foot
- Neem Seed Meal: ½ cup per 1 cubic foot
- Kelp Meal: ½ cup per 1 cubic foot
- Glacial Rock Dust: 1 cup per 1 cubic foot
- Gypsum Dust: 1 cup per 1 cubic foot
- Oyster Shell Flour: 1 cup per 1 cubic foot
- Basalt Dust: 1 cup per 1 cubic foot
- Add-ons and Extras
- Endomycorrhizae powder: enough to cover plant roots entirely
- Worm Castings: 1 cup per 4 square feet surface area
- Cover crop mix: enough to seed all of your pots
How to make super soil
The how-to guide below will give you in depth information on how to make this super soil mix. You can click the section headers to jump around on the page and learn more!
- Before we get started
- Choose your containers and mixer
- Determine the volume of soil you need
- Add your base materials
- Add in the minerals and nutrients
- Mix all the materials
- Test your soil
- Add endomycorrhizae to plant roots and put your plants in soil
- Top dress and mulch
Before we get started
You may want a refresher on the basics of soil science. Check out our beginner’s guide to living organic soil for a solid crash course in agronomy. Understand why this super soil recipe works and you can master your grow.
Credit for pioneering this soil mix goes to Clackamas Coot. He shared this soil mixing technique on a popular online grow forum and it has helped many organic growers succeed since then. Subcool is another forum-famous grower who helped spread soil recipe knowledge, though my recipe differs significantly from his suggestions, I give him a lot of credit for opening up opportunities. Drew Plebani from Commercial Cultivator provided me with rich detail on how he makes his own soil mixes and this post wouldn’t be the same without his help.
In the tech industry there is a lot of talk about “standing on the shoulder’s of giants”. The soil industry applies the same philosophy – build upon the work of others to create new innovations!
In this guide, I tweak certain aspects of Coot’s famous mix based on some new discoveries. This soil mix provides consistent results for everyone from small scale to commercial growers.
This recipe is a solid starting point to learn about living organic soil mixing. Consider it as a baseline for high performing soil. I encourage you to experiment and further “dial in” the soil to your specific needs.
I will be digging into more advanced techniques in future posts, so be sure to subscribe for updates!
Choose your containers and mixer
It all starts here.
Containers are great because they are modular. You manage your risk by keeping everything separate. If something goes wrong in one container it doesn’t take down your entire grow.
So what containers are you growing in?
A perfect container would be the size of your plant’s expected drip line. That is not always realistic, so try to have your container be at least half of the drip line.
If you are using smaller containers, make sure they are not restricting root growth. You may also need to add more frequent amendments to your super soil. That is not a necessarily bad thing, but something to keep in mind when planning your grow.
Pots are usually sized by the gallons, so browse around until you find what works for you. Just remember that more roots mean more shoots, and more shoots yield more loot.
There are three main options when choosing containers:
1. Fabric pots
These are an industry standard, and will work just fine for any type of grow. Smart Pot is the best manufacturer of fabric pots out there today.
2. Air pots
The innovative design on these pots increases soil aeration. For most growers that use them, their plants root out quicker and the plants veg out bigger. Holes on the side also let roots come through so you can do simple root pruning. These pots make it easy to transplant and clean since you can take them apart and lay them flat.
Beds will be your best bet long term on a larger grow. If you can put wheels underneath the beds, you are set up for success. The beds are shallower and wider than pots, and you can plant several plants in each one. This allows roots and mycorrhizae to spread out further and interact with each other. You also get more surface area to play with for mulches and amendments.
You will also need a mixing container to turn your ingredients in to a uniform batch of soil. The size of the mixer you need depends on the volume of ingredients you are working with. Make things as easy as possible for yourself here. Tarps, troughs, or any similar basin is fine to use so long as they hold all the material and is easy to work with.
Determine the volume of soil you need
Now that you have chosen your container gallon size, it’s time to find out how much soil will fill them all up.
You need to translate the gallon measurement of your containers to cubic feet of soil.
Cubic feet is the measurement for soil volume. Gallons measure as either dry or liquid, which can sometimes be confusing. When you are purchasing materials always check to see how the store measures volume. In this guide I use the liquid gallon measurement. 1 cubic foot of soil = ~7.5 liquid gallons.
Use the calculation below to determine how many cubic feet of super soil you need to fill your containers.
(Number of containers * gallons per container) / 7.5 = cubic feet of super soil
This equation gives you the “total volume” of super soil that you will make out of base materials in the next steps.
Add your base materials
This is the foundation of your super soil mixture. The most basic recipe is a 1:1:1 ratio of humus : peat : aeration. I added in the biochar as 10% and split the humus section as half compost and half worm castings to make the super soil even better.
Compost: 15% of total volume
Compost is an organic matter food source for microbes. It also provides a physical structure for plants, has a solid NPK analysis, and generally a neutral pH. A well developed compost in your soil mix is the replica of a natural humus in outdoor soil.
Sourcing high quality compost for your super soil is essential. There are major two factors that affect compost: what they made it out of and what they did with it after they made it.
Buy your compost from a reputable source. If you can find “tea grade” compost, that is likely a winner. Trustworthy sources provide biological data and guaranteed NPK and pH analysis. High quality compost is made from a consistent process and a diverse food source. Smaller batches that are well cared for will provide the best results. The best thing to do is make your own!
Worm Castings: 15% of total volume
Vermicompost is nutrient dense, improves porosity, and has a low chance of carrying pathogens.
Quality is essential here. Many vermicompost companies pass off subpar material as premium product. The best castings come from diverse food sources and are properly screened.
Find yourself some good worm castings with baby worms or worm cocoons. Buy worms separately if you can’t find castings with worms included. Live worms will give you a ridiculous supply of continuous worm castings!
Peat: 30% of total volume
Spaghnum Peat Moss, usually sourced from Alaska or Canada, is the industry standard. It has a low pH as well as amazing water retention and aeration capabilities. This helps build your soil structure and provides a organic wonderful food source for microbial life.
Scoria: 30% of total volume
As an igneous rock, Scoria provides complex shapes with massive surface area. These features increase porosity, aeration, and permeability. Microbes also get to enjoy the porous playground for hunting and hiding. Scoria will have a slightly higher pH, and is also a paramagnetic rock.
Super soil recipes often call for perlite as a way to similarly increase porosity, but you should avoid it if you can. It is expanded volcanic glass that does not lend itself to mimicking the natural soil system except for creating more pore space.
Biochar: 10% of total volume
This stuff is incredible. The char is made from slowly roasting organic matter until it turns into dark earth. By using this material your soil will get a huge CEC and porosity increase. A single gram of biochar has hundreds to thousands of square feet surface area that microbes can use. The biochar and scoria alongside each other provide varied porous textures throughout the soil. In my opinion, microbes enjoy having that variety.
Add in the minerals and nutrients
These materials emulate a natural soil’s diverse sand, silt, and clay particles. Microbes break them down into plant available nutrients and the soil system moves forward. These ingredients improve soil structure, moisture holding properties, nutrient availability, and microbial activity.
Crustacean Meal: ½ cup per 1 cubic foot
A mix of ground up crustaceans, and ideally also salmon. The product that growers traditionally use is a crab and shrimp meal. These sea creatures provide nitrogen, calcium, phosphorus, magnesium, fungi-specific foods, and bug control. The chitin in these crustacean meals is an incredible ingredient for your soil.
Neem Seed Meal: ½ cup per cubic foot
This is also called Neem Cake and is rich in macro and micro nutrients. It helps protect against insect pests, and worms love the stuff.
Kelp Meal: ½ cup per cubic foot
Using this ground up seaweed provides tons of macro and micro nutrients to the soil. It also stimulates plant hormones to enhance vigor, pest resistance, and disease tolerance.
Glacial Rock Dust: 1 cup per 1 cubic foot
This material has available iron, calcium, magnesium, potassium, and a diverse range of micronutrients. It also increases plant-available phosphorus.
Gypsum Dust: 1 cup per 1 cubic foot
It has a neutral pH, and contains large amounts of calcium and sulfur.
Oyster Shell Flour: 1 cup per 1 cubic foot
Oyster shell flour has extremely plant-available calcium. It comes along with a slightly higher pH and helps to buffer the low pH of the peat moss in the mix.
Basalt Dust: 1 cup per 1 cubic foot
Basalt is a lava flow rock that is high in micronutrients. It also has paramagnetic properties.
Mix all the materials
Pour all your ingredients in to your mixing container. Use your hand or a tool to turn over your super soil until the mix looks consistent. You do not have to get it perfect! Nature is forgiving. Materials will naturally move around and settle in your container after planting, anyways.
There is no need to “cook” this super soil recipe. Yet, if you do want to cook your soil, I suggest doing it outside so that you can attract local beneficial biology.
Test your soil
To make the best super soil for cannabis, you first need to identify its needs. After you know what is lacking, you can accurately correct any imbalances.
Now that you mixed your soil you should test it for favorable pH and biology. You can do these tests yourself with the proper equipment or you can send the material to a lab. The lab tests are relatively inexpensive for a professional evaluation.
Why does a pH test matter?
All the individual ingredients that you mixed together have varying pH levels. You want your mix to end up in the best pH range for cannabis. That way, your plants are not stressed at the start and can focus on growing. This optimal pH range is between 5.5 to 6.5.
Why does a biological assessment matter?
Starting your soil with a balanced biology will make growing so much easier. With an early soil food web you can track and alter microbes to maximize growth and better understand what is happening in the soil. Your soil is in a good starting spot when all microbe populations are present, and ideally has a 1:1 ratio of bacteria:fungi.
Many organic soil recipes end up lacking arthropod, microarthropod, protozoa, and beneficial nematode populations. If those or other microbes are out of balance, you can correct the soil food web with two approaches.
- The broad spectrum approach: Use a compost tea base with enhanced levels of the desired microbe populations and brew it so that you extract what you want, which you then apply to the soil.
- The specific approach: Selectively purchase the required microbe populations and apply those directly to the soil.
Biology is individual to each batch of soil and you should handle it on a case by case basis. Know what the biology needs and figure out the best way to mix it in.
Add endomycorrhizae to plant roots and put your plants in soil
Pack your planting pots loosely with super soil.
Dust the roots of your cannabis plants with endomycorrhizae powder. Endomycorrhizae is a fungi that only grows in contact with plant roots and gives your plant a huge boost. As your soil progresses, these same fungi will grow and shift the soil more fungally dominate. Your cannabis plant is going to love that.
Now that you have the super soil ready and plant roots covered in spores, place your plant in the pot’s topsoil. Just be sure not to plant too deeply!
Top Dress and Mulch
Worm Castings: 1 cup per 4 square feet surface area
This is a rough measurement, you more so just want to topdress with a heavy sprinkling of castings. Use the same high quality worm castings that you added in to your base soil mix. Scratch the castings into the top two inches of the soil surface. If you have some worms or baby worms, throw them on top as well. Make sure not to have organic matter touching the stalk or leaves of the plant!
Mulches are a standard part of soil ecosystems. They enable biological activity at the top level of your soil and decrease evaporation.
There are many varieties of dry mulches that you can apply to your grow. In order of quality the scale generally goes like: barley, oak, wheat, alfalfa hay, rice straw.
For this recipe I recommend using cover crops as a living mulch. As they grow, their roots develop their own microbiological activity which enhances the soil. Cover crops remove excess moisture by using water that your cannabis roots could not otherwise reach. When they die, the living mulch becomes dry mulch and an organic biodegradable food source.
Clover is the most pervasive cover crop across all the seed mixes. It is a simple and effective place to start when learning to work with a living mulch. You can use either a clover blend or a batch of pure crimson clover.
That’s how you do it. You can grow the best cannabis by using an organic super soil mix like this.
The end product is a result of balancing quality ingredients and listening to what the soil tells you.
Have fun experimenting on top of this recipe to fine tune it for your grow.
If you liked this could you spread the love and share it with your friends?
What’s your mix? Let me know in the comments below!