How To Make The Best Soil Mix For Growing Cannabis

Soil provides the very foundation of productivity and health when it comes to growing cannabis. This natural medium contains nutrients, microbes, and moisture—everything a plant needs to grow from a cute little seedling into a canopy loaded with dank flowers.

You might look at soil and see an inert, lifeless substance. Why would it even require a second thought? Well, this article might just change your perspective. Using high-quality soil makes the difference between an average outdoor growing season and an excellent one.

Below, you’ll learn how to create the best-quality soil possible, one teeming with nutrients and beneficial organisms that enhance your harvest and combat disease.

WHY TOP-NOTCH SOIL IS SO IMPORTANT WHEN GROWING CANNABIS

Cannabis plants obtain most of the substances they need to survive from the soil, with the exception of hydrogen, carbon, and oxygen. But soil doesn’t just provide a pool of nutrients; it hosts a world of lifeforms that influence and benefit cannabis plants.

GIVES PLANTS ALL THE NUTRIENTS THEY NEED

What makes you feel better, a bag of crisps or a bowl of fruit? As humans, we need the right nutrients to feel good and perform at our best. Cannabis plants are no different. If we miss out on a particular vitamin or food group, we start to feel the impact and can even become deficient. The same applies to our herbal friends.

While we rely on several food groups and a balanced diet, cannabis plants require nutrient-dense soil to meet all of their demands. High-quality soil features large amounts of nutrient inputs in the form of organic matter such as mulch and compost.

Over time, this matter breaks down—with the help of beneficial microorganisms—and releases nutrients into the soil. Cannabis plants have a high demand for three primary macronutrients:

• Nitrogen
• Phosphorus
• Potassium

Plants also require several micronutrients. They don’t need as much of these elements, but they still play a fundamental role in plant health and physiology. These include:

• Boron
• Calcium
• Copper
• Magnesium
• Manganese
• Molybdenum
• Sulphur
• Zinc

High-quality soil will provide cannabis plants with all of the nutrients they need to get the best start in life. Spending time preparing the soil will pay dividends at the end of the growing season in the form of massive yields and luscious plants!

PROMOTES PLANT HEALTH

Poor-quality soil simply won’t contain all of these key nutrients. This can lead to deficiencies that slow plant growth, reduce harvests, and even kill plants. But good soil provides more than just nutrients; it provides a living growing medium.

Plants don’t simply suck nutrients out of organic matter. First, these materials need deconstructing. Living soil contains many microbes and insects that make up the soil food web. These lifeforms break down compost, eat each other, and liberate nutrients into plant-available forms. This complex dance of life brings plant health to another level and builds healthier and more biodiverse soil year after year.

PERFECT ENVIRONMENT FOR ROOTS

We all know cannabis plants are alive, but just how intelligent are these fascinating beings? Advances in soil science suggest they are a lot more clever than we give them credit for. High-quality soil provides an ideal environment for their roots—the bridge between plants and the soil world below.

Have you ever heard of the rhizosphere? This word refers to the region of soil that spans several millimetres from the outside surface of the roots. Plants excrete sugars created during photosynthesis into these regions. Many beneficial organisms are attracted to these so-called exudates.

Bacteria, for example, love the taste of these sugars. But with plants treating them to such precious resources, what do they get in return? Well, bacteria also break down organic matter. They are essentially little sacs full of nutrients. When they die, they release these nutrients into the rhizosphere for plants to consume.

Exudates also attract another plant ally: mycorrhizal fungi. These species form a physical connection to plant roots. In exchange for tasty sugars, they act as an extension of the root system, digesting organic matter and shuttling nutrients into root cells.

Easy Roots Mycorrhiza Mix

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Cannabis roots thrive in high-quality soil thanks to the biodiversity it generates. Poor-quality soil simply doesn’t possess the same quantity or quality of microbial life.

WHY YOU CAN’T USE ANY OLD SOIL FOR YOUR CANNABIS PLANTS

After diving into the rhizosphere, it becomes apparent that throwing your seeds into any old soil won’t guarantee success. This brings us to an interesting comparison: soil vs dirt. Soil features a living matrix of life and a rich bank of nutrients that helps cannabis plants survive and thrive. Dirt features much less nutrients, organic matter, and beneficial microbes.

Cannabis plants will always fall short of their full potential if they don't have access to all of the nutrients they need. Nutritionally void dirt will give rise to stunted plants with less vigour and smaller yields. Living soil houses all the minerals cannabis plants need, along with the microbial life that makes these important nutrients available.

By investing in healthy soil—or building your own using mulch layers and composting—you'll unleash the full genetic potential of your favourite strains.

THE PERFECT BASE SOIL FOR YOUR CANNABIS PLANTS

The perfect soil might sound like a bold claim, but you can achieve this at home with little work. Our formula consists of two primary parts: a base soil that serves as a growing medium early in the cycle, and a super soil that adds extra nutrients to see plants all the way from the vegetative phase to harvest time.

Our perfect soil blend removes the needs for additional organic nutrients and amendments. The base soil and super soil sit in two distinct layers. The base soil occupies the surface of the bed or container, while the super soil resides underneath.

Young plants thrive in the base soil and begin taking in nutrients. Eventually, their roots extend down into an incredibly rich source of nutrients—super soil—that provides everything else they need. This makes things very easy for you as the grower. Just water when necessary!

When selecting a base soil, you have basically two options. First of all, you can buy a base soil in a gardening centre or you can use homemade compost as your base soil.

BUYING BASE SOIL

Growers can simply buy base soil from a store or gardening centre. Purchase high-quality organic compost with at least some of the following ingredients:

• Coco fibre
• Perlite
• Compost
• Peat moss
• Bone meal
• Bat guano
• Kelp meal
• Greensand
• Soybean meal
• Worm castings
• Mycorrhizal fungi

Chances are you won’t find soil with all of these exact ingredients, but don’t worry. Any organic soil with just a few of them will suffice.

USING HOMEMADE COMPOST

If you make your own compost at home, you won’t need to buy base soil at all. Composting converts kitchen scraps and garden waste into a nutrient-dense growing medium suitable for mixing with regular soil and use as a base soil.

Compost piles consist of a mix of green and brown materials. Green materials such as grass clippings, kitchen scraps, and manure provide high levels of nitrogen. Brown materials like twigs and cardboard provide a source of carbon. The correct ratio of these materials creates an optimal environment for beneficial aerobic bacteria to break down this organic matter and release its nutrients over time. Worms will also turn up to the party, feast on the goods, and poop out highly nutritious worm castings.

Overall, composting is a superb way to create a highly valuable resource using a closed-loop system. It reduces your carbon footprint and enables you to transform waste into an effective growing medium.

CREATING SUPER SOIL

With your base soil ready for action, you’ll need to make your super soil next. Check out the ingredients and equipment you’ll need, as well as how to make it, below.

INGREDIENTS

• 2 large bags (2 x 40l) of base soil or the equivalent in homemade compost
• 5–10kg organic worm castings
• 1kg blood meal
• 1kg bat guano
• 1kg steamed bone meal
• 750g rock phosphate
• ⅛ cup Epsom salts
• ¼ cup azomite
• ½ cup dolomite
• 1 tbsp. powdered humic acid

HARDWARE

• Tarpaulin
• Rake
• Spade
• Large buckets or plastic garbage cans

INSTRUCTIONS

1. You now have everything you need. Follow the steps below to make your own super soil ready for use in the garden.

2. Clear a large space in your garden or garage.

3. Lay down a large tarpaulin to prevent losing materials.

4. Create a mound of base soil or compost in the middle.

5. Using a rake, spread a layer of worm castings over the top, and cover with another layer of base soil.

6. Now, add the bat guano, followed by more base soil.

7. Keep adding layers of super soil ingredients, followed by a final layer of base soil, until you’ve worked through the list.

8. Use a spade to thoroughly mix the ingredients into a homogenised substrate. It should take around 20 minutes (and a bit of sweat) to get them all blended well.

9. Load the mixed soil into large buckets or plastic garbage cans for storage or use right away.

HOW TO PLANT YOUR CANNABIS IN YOUR SOIL MIX

You did it! You made your own perfect soil blend ready to give rise to some incredible cannabis plants. Before you start plunging your seeds into the soil out of pure excitement, we need to cover exactly how to use it.

PREPARING YOUR POT

Super soil will help mature plants thrive, but the nutrient-rich medium can easily burn or kill young seedlings. Fill your empty pots to 30–50% capacity with super soil. Then, fill the remaining space with base soil. This will give your young plants time to mature before they make contact with the super soil below. We recommended using Zamnesia Geotextile Fabric Pots for improved moisture retention and optimal aeration.

WHEN TO TRANSPLANT

After starting your seeds and allowing them to reach 2–3cm in size, they’ll be ready for transplanting. Larger photoperiod strains can be potted up through several sizes until placed into their final vessel. Only pot up into base soil during the first transplant to avoid nutrient burn.

Fast-growing indica varieties or autoflowers can be placed directly into their final pot. The thick layer of base soil will give them time to mature before they reach the super soil layer below.

MAINTENANCE

Using our perfect soil mix makes growing incredibly easy. You won’t need to constantly mix up nutrient concoctions or add top dressings to your growing vessels. Just make sure to water your plants correctly, and you’re good to go. Wait for the top layer of soil to completely dry out before hydrating your plants once again.

Luke Sumpter

With a BSc (Hons) degree in Clinical Health Sciences and a passion for growing plants, Luke Sumpter has worked as a professional journalist and writer at the intersection of cannabis and science for the past 7 years.

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