Apr 13, 2018

What is Super Soil? A Professional Review

“The best part about it is the consistency. I rarely, if ever, see any nutrient deficiencies, across various plant types.”

What is Super Soil?

Super soil is a term coined by well-known grower and seed producer Subcool to describe a soil recipe he uses to help simplify the process of attaining an ideal harvest no matter your level of growing expertise. It is a highly amended growing medium that eliminates the need to use liquid nutrients. Subcool, who operates TGA Genetics, has been a contributor to a variety of magazines. He has won awards, is an accomplished author, and has over 30 years of experience as a grower.

Do you want a super easy, low-maintenance way to grow organically?

The theory behind Super Soil is that by creating a well-balanced and nutrient-dense growing medium, you should never have to adjust for pH or nutrient imbalance. All you have to do is water! Because Super Soil creates a very “hot” or nutrient-dense soil, you will want to be careful about how you use it. Super Soil is a concentrate to be used in addition to base potting soil. Below we have the recipe, along with specific instructions on how to build and use Super Soil in your garden.

There are benefits and drawbacks to using Super Soil, so before we really dive in, here are some things to think about if you are considering using a highly amended soil recipe:


  • Organic growing method
  • Saves money on fertilizers
  • Saves time on pH adjustments
  • Nutrient-dense so it grows strong plants
  • Mimics natural outdoor growing environment
  • No need to flush plants


  • “Cooking” time can be long and inconvenient
  • Potential to burn plants if not used properly
  • Not as easy to manipulate as liquid fertilizers
  • Yields may not be as large as with synthetic nutrients
  • The growth cycle may be slightly longer than with liquid nutrients

Plant Nutrition 101

All plants need nutrients from the soil for healthy growth. Along with light and water, nutrients are crucial for plant development. Plants require macronutrients in the largest amounts, and although micronutrients are needed in much smaller amounts, they are still a necessity for viable plant growth.

Primary plant macronutrients:

  • Nitrogen: promotes healthy and fast vegetative growth
  • Phosphorus: promotes root growth, flowering and fruiting, and disease resistance
  • Potassium: helps with fruit ripening, disease resistance, and overall plant health

Secondary plant macronutrients:

  • Magnesium: helps plants process and utilize calcium, promotes vegetative growth and sugar formation
  • Calcium: supports the structural integrity of plants, new cellular growth, and disease resistance
  • Sulfur: helps fruits and seeds mature and promotes the growth of green leaves

Plant micronutrients:

Micronutrients are trace elements that help promote green leaf growth as well as starch formation. These include boron, chlorine, copper, iron, manganese, molybdenum, and zinc.

Super Soil is so effective because it takes into consideration every one of these plant nutrients. Each ingredient in the recipe provides one or more essential plant nutrients to your growing medium, making it an ideal mixture for plants.

For more information on plant nutrition and how to diagnose nutrient deficiencies, check out our plant nutrient basics


Super Soil Recipe

  • 14 cubic feet (or 8 large bags) of Roots Organic Original Potting Soil
  • 1 cubic foot bag Roots Organics Big Worm Worm Castings
  • 2.5 lbs. Down to Earth Bone Meal
  • 2.5 lbs. Down to Earth Fish Bone Meal
  • 5 lbs. high phosphorus Sunleaves Jamaican Bat Guano or VermiBat
  • 5 lbs. Down to Earth Blood Meal or VermiBlood
  • 3 cups Down to Earth Oyster Shell
  • 3 cups Down to Earth Kelp Meal or VermiKelp
  • 3 cups Down to Earth Alfalfa Meal
  • ¾ cup Pennington Epsom salts
  • 1 cup Speedi-Grow Agricultural lime
  • 2 cups Down to Earth Azomite
  • 2 Tablespoons Down to Earth Granular Humic Acid
  • 2 Tablespoons Mykos Mycorrhizae (per transplant, applied directly to the roots [STEP 6])


  1. Mix all ingredients either on a large tarp, in a small kiddie pool, in a yard waste trailer, or even in the bed of a pickup. You can choose to leave out the mycorrhizae here and apply them directly to the root ball when transplanting. If you choose to include mycorrhizae at this step they will remain dormant (usually encased in clay) until it comes in direct contact with live roots.
  1. While mixing, moisten the media just enough to promote humidity, not enough to drench it.

  2. Once mixed, you can transfer it to several lidded containers like 35-gallon trash cans, or large totes, or just cover it with another tarp. Keep it in a warm area for a minimum of 30-45 days, up to 90 days to “cook”, or start the process of breaking down amendments.
  1. After this waiting period, you will want to fill the bottom ¼ to ⅓ of your pot with this Super Soil mixture and then top with another couple of inches of base soil.
  1. Gently mix the top layer to create a buffer zone between the base soil and the Super Soil. Then fill the rest of the way with base soil, creating a hole in the center of the dirt- this is where you are going to gently set the root ball of the transplant.

  2. Remove the plant you are planning to transplant from its container. Apply mycorrhizae directly to the root ball. Mycorrhizae need direct contact with living roots to snap out of their dormancy and cultivate properly.

  3. Finish packing the plant in with base soil. From this point, you should only need to water- no pH necessary unless you know your water supply can be unpredictable.

Hydroponic garden using super soil

Super Soil is a very nutrient-dense soil concentrate, so you never want to plant directly into the mixture or you risk subjecting your plant to nutrient burn.

Super soil can be a lot of work to get set up, but for the growers who choose this method, the benefits are well worth it.

To get more familiar with the ingredient list, let’s dive into the purpose behind the specific amendments in this recipe.

What is the purpose of the ingredients in Super Soil?

High-quality organic potting soil with coco and mycorrhizae.

Coco is a by-product of the coconut industry and is an environmentally friendly alternative to using peat. As coir breaks down, it also releases potassium, serving as both a potential nutrient source, while also increasing the structural integrity of your growing medium.

The benefit of mycorrhizae in your grow medium is indispensable, so finding a good base soil that includes it is important. You can also add it separately, as we have shown in our recommendations for the recipe. Mycorrhizae are beneficial fungi that attach themselves to the roots of plants. Once attached, they help plants to better process and utilize nutrients more efficiently.

Worm castings are the waste products from earthworms that serve as an excellent organic fertilizer. Worm castings are high in nitrogen, one of the three primary plant macronutrients. Worm castings are coated with special oil as they travel through Earthworms. This oil takes time to break down, which makes worm castings a very effective, slow-release nutrient source that can feed plants longer than other fertilizers. It is because of this that the nitrogen in worm castings is particularly helpful at promoting vigorous vegetative growth.

Bone Meal and/or Fish Bone Meal are good sources of Phosphorus.  Bone meal has the added benefit of containing calcium, a secondary plant macronutrient.  Calcium increases the structural integrity of your plants, promotes new growth, and increases disease resistance.

High phosphorus Bat guano stimulates soil microbes and improves plant development and growth. Depending on your nutrient needs, you can generally find either high phosphorus or high potassium bat guano. This recipe calls for high phosphorus guano.

Blood meal is one of the highest natural sources of Nitrogen, which is often the limiting factor in plant growth.

Oyster shells provide slow-release calcium, a secondary plant macronutrient. This is an especially useful amendment if you use Fish Bone Meal, which lacks the calcium you could get from bone meal. In addition, oyster shells help neutralize soil acidity.

Kelp meal is used primarily as a source of trace minerals and plant micronutrients, including potassium. It is also a source of natural plant hormones.

Alfalfa meal adds organic matter and trace minerals to the soil. It also contains triacontanol—a natural fatty acid growth stimulant.

Epsom salt provides magnesium sulfate, a highly soluble form of magnesium, and sulfur, both secondary plant macronutrients. Magnesium also helps the uptake of calcium and may be useful in preventing bottom-end rot in tomatoes.

Dolomite lime buffers pH by neutralizing soil acidity and provides calcium and magnesium to your soil mixture. By serving as a pH buffer, it also makes many micronutrients more bioavailable.

Azomite is primarily a source of sodium and calcium and is high in many trace elements. It may contain as many as 70 individual trace elements, especially silica. Studies have shown that Azomite helps plants better absorb nutrients from the soil.

Powdered humic acid “neutralizes soil pH and liberates carbon dioxide. Once the soil is neutralized, then many trace elements formerly bound in the soil (such as iron in alkaline soils) and unavailable to plant roots, become available to the plant.”
-Dr. Robert E. Pettit, Emeritus Associate Professor of Texas A&M University

The Breakdown

As you can see, Super Soil is a pretty robust concentrate. You can see here the exact source and balance of essential plant nutrients:

Primary plant macronutrients:

  • (N) Nitrogen: worm castings, blood meal
  • (P) Phosphorus: bone meal, bat guano
  • (K) Potassium: coco breakdown, kelp meal

Secondary plant macronutrients:

  • (Mg) Magnesium: Epsom salt
  • (Ca) Calcium: bone meal, oyster shells, dolomite lime
  • (S)Sulfur: Epsom salt
  • Plant micronutrients: kelp meal, alfalfa meal, azomite
  • pH buffer: oyster shells, dolomite lime, humic acid

What do home gardeners have to say about Super Soil?

To give you an idea of what it is like to work with Super Soil, we met up with seasoned gardener Topher Jones to get his take on it.

How long have you been using Super Soil?

I have been using super soil for about two years, or about a dozen or more indoor crop cycles. We stage our crop cycles, so I can let a batch of soil cook for a minimum of 30-45 days, but honestly, the longer the better. The longer you let it cook, you give everything a chance to break down, making nutrients more bioavailable and less hot. The longer you let it cook, the friendlier the soil is for the plants. You have to have a constant batch of super Soil waiting, so you can have a batch at the ready and fully cooked when you are ready to transplant.

What made you decide to make the switch to super soil?

I have always liked the idea of organic, natural-style growing and saw the benefits of saving time by not having to pH and mix nutrients for all different stages of growth. I was looking for something low-maintenance on daily chores. With multiple rounds in different stages of flower, it was a no-brainer to not have to mix different batches of water and nutrients for each phase group. I have also been continually learning and helping other people learn about their plants and grows, so Super Soil gave me a simpler platform to learn and figure things out as I went along and developed my grow more.

Do you modify your recipe from the original Subcool recipe?  Why?

Generally, I keep the original recipe for the most part, but I sometimes add more perlite and stay on the low end of worm castings. It says 25-50lb of worm castings in the original recipe and 50 pounds just seemed like a lot to me. I use 25 pounds of worm castings and that seems to be enough—you get a lot of nitrogen from the blood meal, too. For Perlite, I add about 4gal by volume for every 2 gallons of soil because I like a more aerated soil. My plants seem to like it more too.

Do you do any other modifications during your grow cycle?

I feed with compost teas two weeks after flower and two weeks before harvest to keep bacteria and micro-life alive and thriving and add a little nutrient bump at the end. It helps fully digest the amendments in the soil mix. I also tried Mammoth this last grow cycle instead of compost tea and had great results. It bumped up my yield by potentially as much as 33%, but it’s too early to tell for sure. I was pretty happy with the results, though, and am considering using it again. I’m thinking about trying a new compost tea recipe and attempting to match results with Mammoth. That might be hard to beat, though.

Have you noticed a difference in your overall plant quality with Super Soil?

Plant quality is high, but the best part about it is the consistency. I rarely, if ever, see any nutrient deficiencies, across various plant types. Minimal in-cycle work is a major plus. Flavors and smells are fantastic with Super Soil- you can’t beat organic growing and I never have to worry about flushing my plants.

Do you have any final comments for our readers?

For people who like growing organically and have busy schedules, I recommend a form of Super Soil or a highly amended growing medium for a great way to grow quality product.

Thanks for your input, Topher!

 The More You Know, the Better You Grow!

Despite the evolutions of Subcool’s Super Soil recipe, the basics have stood the test of time. You can see there are some major benefits to making the switch to organic Super Soil! Stop in today to one of our locations if you think Super Soil might be right for you!