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What is super soil and how do you make it?

June 19, 2017
Trevor Hennings and Patrick Bennett contributed to this article.

If you’re thinking about getting started in the exciting world of organic cannabis cultivation, you’re going to want to learn a thing or two about the soil you plan to use. After all, a proper organic substrate is quite possibly the most important and often most overlooked aspect of the entire cultivation process.

When we think of soils, a pre-mixed plastic bag often comes to mind. Admittedly, it’s pretty easy to just dish out $20-$30 for a bag to start your grow. Many of these pre-mixed “super soils” are, in fact, organic and act as a terrific starting point for novice gardeners.


How to Grow Organic Cannabis at Home

However, building your own soil at home can be just as easy, cost-effective, and accessible as buying a pre-mixed back at the store. Creating your own super soil will also teach you a few great tips on soil science and how the component of your substrate will effect the outcome of your cannabis grow.

In the first part of our organic super soils series, we’ll explain they are and why they’re important for your cannabis, plus we’ll share some handy steps to consider when building organic soil for your grow.


Using Veganics for Growing Organic Cannabis

What is an organic super soil?

The key factor in organics is soil life. A proper organic soil, in the words of famed organic soil scientist Jeff Lowenfels, is “teaming with life.” To put this into perspective, a shot glass filled with a proper organic soil will contain more individual living organisms than humans that inhabit the planet. That’s a lot of life!

Each organism within this habitat serves it purpose in the web of life (sometimes also referred to as a soil food web). This web is not only virtually self-sustaining, it also has the capabilities to both convert and provide readily available nutrients to your plants. Maintaining an organic cannabis garden grown in super soil may require little to nothing more than adding water. Take that, synthetic nutrients!


Organic vs. Chemical Cannabis Fertilizers for Your Grow

The term“super soil” has been floating around the organic cannabis community for some time now. Its origin dates back to when organic cultivation practices were just beginning to make their way into the canon of cannabis grow methodology. Perhaps the undisputed king of organic super soils is Subcool of TGA Genetics, who a few years back posted his super soil recipe in a High Times article. Since then, his recipe has served as the de facto totem for the organic cannabis cultivation community. Virtually every subsequent article on organic super soils references SubCool’s soil recipe, and for good reason: it works.

4 steps to building organic soil for cannabis

Growing cannabis organically allows growers to raise a high-quality product without the interference of chemical nutrients that can burn or kill the plants. To create a soil that provides the perfect environment, you’ll need a basic primer on how best to work with it and what nutrients are required to help your plants thrive. It’s important to truly understand what you want in your soil so that you can produce your own custom blend that costs less and contains all essential nutrients.


What are the best nutrients for growing cannabis?

Follow these steps to better understand what makes ideal soil and how to build it in your own cannabis garden.

Step 1: Know what’s in your soil

Chicken manure


To build a quality soil, you first need to know what’s in it to begin with. When buying soil, you’ll see a list of ingredients and information on what nutrients are readily available in it. If you’re hoping to use soil that is already in your garden or being taken from another source, it’s impossible to readily know what is actually in that soil. To remedy this problem, you can submit a soil test that will give you a base understanding of what nutrients it contains.

Additionally, you can work your hands through the soil and get to know it. Is it compact or fluffy? Is it sandy or claylike? Does it hold moisture or is it dry? Are there worms and insects present? These are all things you can consider by simply using sight and touch.

Step 2: Find the right soil amendments

Chicken manure


Once you’ve gotten to know your soil’s nutrient levels and texture, it’s time to add any necessary soil amendments. The basic building blocks for plants are based around N-P-K. This stands for nitrogen (N), phosphorus (P), and potassium (K). To build a strong healthy soil, it should have these nutrients readily available for your plants to absorb.

Nitrogen-rich nutrients:

1. Worm castings

Providing a quick-release source of nitrogen for your plants while also introducing healthy bacteria, worm castings contain many micronutrients depending on where they are sourced from.

2. Crustacean meal

A little slower to release than worm castings, crustacean meal adds nitrogen, phosphorus, calcium, and chitin to your soil. Chitin-eating microbes will help keep nematodes at bay.

3. Bat guano

Bat guano provides the highest levels of nitrogen and phosphorus of all these listed nitrogen amendments. It does wonders for sustained plant growth while diversifying the soil’s bacteria and microbes.


Spider Mites, Fungus Gnats, and Root Aphids: How to Deal With 3 Common Cannabis Pests

Phosphorus-rich nutrients:

1. Bone meal

Bone meal generally comes from cattle bones, and it helps to keep phosphorus levels up. Keep in mind that your soil needs to be at a pH below 7 for bone meal to be most effective.

2. Chicken manure

Chicken manure is a great way to introduce both phosphorus and nitrogen. Choose a high-quality manure that is fully processed and make sure to amend the manure into your soil with enough time to let hot manure cool off.

3. Rock dust

Rock dust is a very slow-releasing phosphorus source that can be effective in soil for years, but it does not perform well in soils with a pH above 7.


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Potassium-rich nutrients:

1. Kelp meal

Kelp meal is a great source of potassium that promotes microbial diversity in the soil. A water-soluble amendment, kelp can be applied with water or by hand directly into the soil.

2. Wood ash

Wood ash can be used to increase the potassium levels in your soil, but be aware that it generally raises the pH so make sure to test your soil’s pH levels regularly.

3. Compost

Your compost bin can be an excellent source of potassium for your garden, especially if it contains fruit rinds and banana peels.


How to Make Compost Tea for Cannabis Plants

These three basic N-P-K amendments are most important, but there are also micronutrients that will help your plants grow. Products like gypsum, azomite, and kelp meal can add many micronutrients to strengthen your soil. When it comes to soil, a wide diversity of nutrients can introduce nuanced flavors, aromas, and effects in your end product.

You should also consider amendments that change the soil’s density, airflow, and ability to hold water. For example, perlite and peat moss can improve drainage and water retention. Introducing a healthy worm population and fungal colonies will also help fluff up the soil, thus improving its structure. A healthy soil maintains itself, and living organisms both reap and share the benefits of a healthy soil with your cannabis plants.

Step 3: Mix your soil

Soil tiller


To till your soil, apply the amendments and start digging or use a rototiller. It takes time, but make sure everything is adequately mixed and that all corners of the pot or bed have been reached.

Once you’ve mixed everything in, water your soil to help cool any added manure. This process should be repeated every few days until the soil is cool to the touch when you bury your hand. At this point, the soil is ready for your seeds or clones.

Though tilling your soil is necessary for your first year as a gardener, it’s up for debate whether or not tilling annually is beneficial. The argument against tilling is that it breaks down a complex network of mycelium, worm tunnels, and cavities created by beneficial organisms in the soil. However, by tilling your soil annually, you can easily add amendments and break down cover crops, thus making sure all the nutrients in the soil are mixed and readily available.


How No-Till Cannabis Farming Methods Can Improve Your Crop

Still not sure whether to till or not to till? Try analyzing soil samples at the beginning and end of the season to determine whether or not annual tilling benefitted your garden in the end.

Step 4: Prepare your soil for the next season

Growing radishes


To protect your soil for the next season, remove the stalks and roots of the previous cannabis plants; you can compost and re-apply them to your soils once they’ve decomposed.

Next, introduce a cover crop to your soil to help maintain it during winter. Common crops include legumes or radishes. Legumes sequester and preserve nitrogen while radishes have long taproots that help aerate and free up deep, compacted soils. These cover crops need to be destroyed before they go to seed. This can be accomplished by tilling or cover mowing to kill the plants.


Stages of the marijuana plant growth cycle

In the offseason, you can add nutrients back to your garden by top dressing the soil. Adding compost, manure, and other amendments and allowing rainfall to bring the nutrients into the soil is a great way to improve the soil quality in the offseason without having to do much work.

Building your own soil is a rewarding investment that will only strengthen your understanding of gardening and how plants grow and thrive. With quality soil, you will find the need for liquid feeding to be greatly reduced, saving you time and money. You’ll also find that the soil becomes a sanctuary for other living things as you improve the environment surrounding your garden.

In Part 2 of our super soils series, we’ll share a simple recipe you can build at home for your cannabis grow.

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Leafly Staff

Leafly is the world’s largest cannabis information resource, empowering people in legal cannabis markets to learn about the right products for their lifestyle and wellness needs. Our team of cannabis professionals collectively share years of experience in all corners of the market, from growing and retail, to science and medicine, to data and technology.

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4 part series