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Simple Soil for Extraordinary Results

July 8, 2016

Professional growers have many options for soil, but it’s best to make a soil mix yourself. Doing this will help you understand what types of soil that cannabis thrives in and how the soil should feel in your hands. You need to make a soil mix rich in beneficial organisms; this will add nutrients to your water. Since cannabis is a fast-growing plant, it will quickly deplete the soil of nutrients.

The goal of making your own soil is to create a biodiversity. The symbiotic relationship among the organisms increases the availability of the added nutrients. A large plant in a five- to 10-gallon container of dirt pulls as many nutrients as it can to bring tremendous results in weight and density.

There are many soil and additive brands on the market. If grow supply stores don’t offer the exact brands we mention, they may know what to use instead. The following cost-effective recipe is for 50 seven-gallon containers.

Recipe for grow mix

First, add three bails total to your base mix as follows:

  • Two bails of Premier Horticulture Pro-Mix BX (3.8 cu. ft.). This contains a beneficial mycorrhizal inoculum in the combination of Canadian Sphagnum peat moss (75-85%/volume), vermiculite and perlite. Mycorrhizae is a fungus that attaches to the roots and works symbiotically with the plant.
  • One bail of Premier Horticulture Pro-Mix BX Biofungicide (3.8 cu. ft.). This can pre-emptively stop problems from arising if you live in areas prone to fungus and mold infections. The BX mix contains a biofungicide that has been inoculated within the soil and will systemically help the plant fight off any fungus spores. This added fungicide is not a full replacement for preventive care of the plants, but it will help with overall health throughout the growing cycle.

Next, add beneficial additives such as:

  • Bat guano. There are two types, one with nitrogen and one with phosphorus. It’s best to add more nitrogen than phosphorus for the vegetative state, up until flowering. If you plan to transplant before you flower, mix in the high phosphorus guano during your last transplant. For an overall one time potting use, your mix will include two bags of guano with nitrogen and one bag of guano with high phosphorus.
  • Earthworm castings. The more, the better. One to two 30-pound bags added in this mix will bring it to life. Cannabis loves earthworm castings, so there can never be too much.
  • Two blocks (or 4 bags) of coconut fibers. These are ideal for both retaining water and helping keep a natural pH balance. The blocks need to be soaked in reverse-osmosis (R/O) filtered water before use; this will let them expand and maintain pH balance. There are many brands of coconut fiber, and your local vendor can advise you on what’s best in your area.
  • Two or three bags of organic compost mix. This additive gives your soil a balance and helps beneficial microbes grow and multiply.
  • 15 gallons of perlite. This helps with both drainage and nutrient availability. Wear a mask when dealing with this product, since the dust can be hard to breathe.
  • 10 gallons of vermiculite. This helps oxygen make it to the roots by keeping the soil from packing.
  • Cal/Mag powder additive blend. You can opt out of this for a liquid form that’s added to your nutrient mix in water feedings. Calcium and magnesium can prevent deficiencies from fast-growing plants. Also, when you water with an R/O-filtered system you must add this to your regimen, either in the soil mix, the watering routine or both—because R/O filtration removes both calcium and magnesium.

By the way, always use R/O water in your grow. This provides a base of zero parts per million to help keep salts and contaminants out of your watering cycle, giving you the perfect base to add nutrients and pH balance agents.

Back to the additives list:

  • Three cups Xtreme Gardening Azos. This works with IAA (indole-3 acetic acid), creating a rapid production of more IAA. This beneficial microbe is a great way to boost growth and increase new root development.
  • Three cups Xtreme Gardening Mykos Mycorrhizae. This is a very particular species of Mycorrhiza that offers stable and stronger microorganism availability.
  • One package of beneficial nematodes. These living organisms kill soil-dwelling bugs such as root aphids and feed on the larvae of thrips and fungus gnats. The nematodes leave behind more useful living soil agents in the waste of the nematodes.

So, that’s the list; now what? The best way to make the soil mix accessible and as easy as possible is to get the largest tarp you can. A 20-foot by 30-foot tarp is a great start, but you may find that you will need a different size.

When adding the ingredients together, it’s best to layer them (think lasagna). For example, if using three bails of Pro Mix, add half a bail. Then add some (not all) earthworm castings. Then add some organic compost. Repeat this until you have layered all the ingredients. This methodology will help with mixing evenly and ensure each plant will have an equal mix.

Using a hoe or a shovel, mix the ingredients. Ask a helper to grab a corner of the tarp while you grab the corner diagonal to your helper. Fold it in on itself from each opposite corner until it is uniformly mixed. Your mix will compress when squeezed in your hand and will expand when the pressure is released.

Finally, lightly add some R/O water and let it sit overnight. It’s best if you wait four to seven days until use, to allow all the living microorganisms to begin inoculating the soil. This soil mix is generally pH-neutral and ready for any combination of nutrients you add to your water. Making sure you pH test your R/O water before use is paramount for success.


By Eric Stone


Cannabis Cultivation Today articles are for informational purposes only and should not be considered legal guidance or advice on grow practices. You should contact an attorney or a qualified cultivation consultant for specific compliance and cultivation advice.


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