Here is a guide on building your own super soil. This recipe was put together by @TempleGrower, who is a member of our cannabis growers forum.
If you are thinking about building your own living soil, feel free to ask for advice in our cannabis growers forum
TempleGrower’s Organic Super Soil Recipe
This is my general ‘super-soil’ recipe that I’ve been using in my indoor gardens for a few years now with very excellent results.
Being that my job can take me away for weeks at a time, I’ve tried to find/come up with something that is basically self sufficient from seedling to harvest, with the only addition being some high quality 6.5-7.0 pH H2O. The basic recipe I started with was Vic High’s Soil Mix #2, but I’ve since tweaked and substituted some of the amounts/ingredients. If you search for either ‘Vic High Soil Mix’ and/or ‘Subcool Supersoil’ on Google, there is a lot more info and background for anyone interested. But just so everyone knows, I didn’t come up with this recipe; just amended it for my local inputs. Full credit to Vic High and Subcool (RIP).
It’s up to you what you like to use but, I try to stick with stuff as local as I can get it, and especially if you can make it yourself (e.g. compost, worm castings, potentially manure, etc.). I live in Saskatchewan so, the stores I use to source ingredients from are Peavey Mart, Home Hardware, Canadian Tire, Home Depot, Costco, etc., but preferably local garden shops/local farmers.
My amended version is as follows:
105L high quality potting soil
- Primary medium – Any good quality potting soil will do – I’ll usually use either the Costco bails (‘The Answer’ – good value @ 12.99/85L, but only available in spring/summer. Made from peat moss/perlite/composted wood bark*), or the blend from Early’s Farm and Garden (more money @ $9.99/55L but always available, and local. Made from peat moss/vermiculite/perlite/loam.) Whatever you like/have available will likely be fine though. Just ensure it’s not ‘pre-amended’ with added fertilizers or water-holding crystals or things like that.
10-15L of worm castings
- N-P-K (trace – depends what the worms ate)/Micronutrients/Microbes/Moisture retention – I use either the Mark’s Choice brand from Home Hardware or the local garden store house brand. This is something you can definitely make yourself though through vermicomposting your kitchen waste. Don’t over-do these though, as they can cause issues with drainage.
3 cups blood meal
- Nitrogen – N-P-K ratio is 12-0-0, and the N is readily available.
6 cups 1/2 Blood + 1/2 Bone Meal
- Phosphorus – N-P-K ratio is 4-10-0, and P is also readily available. Some N in there too.
3 cups dolomitic lime
- Calcium + Magnesium – Plants need Ca and Mg for vital plant processes. Also important as it helps to keep the soil from becoming too acidic by acting as a buffer as Ca- and Mg-bearing compounds react readily with acids, helping to protect the medium’s pH from large swings due to inconsistent water quality, weird soil, experimental amendments, etc.
1 heaping cup of Epsom salts
- Magnesium/Sulfur – Not much to say here but, very important. You can get this from the garden stores, or buy the big jug from WalMart/Costco/etc. Just be sure it is unscented – it should be pure Magnesium Sulphate (MgSO4) with no additives.
5-10L Perlite/Vermiculite (or more if you prefer)
- Drainage – Most mediums have some perlite/vermiculite already mixed in but, not enough for the amount of extra organic material added to this mix. I personally always have used perlite as vermiculite has, in the past, been associated with asbestos (the mines where the mineral (called mica) that vermiculite is made from can also host asbestos-bearing minerals). I don’t think this is an issue anymore, but best to err on the side of caution, in my opinion.
5 heaping spade-fuls of sifted compost OR ½ bag (8-10L) store bought compost/steer/sheep manure
- Water retention/drainage/microbes/Macro & micronutrients – Garden compost is amazing stuff. It promotes proper and even drainage but at the same time helps with water retention (makes sense right? ?) . It’s also LOADED with beneficial microbes/fungi/etc., which help the plants absorb all the delicious treats you’ve added. I make all my own compost at home, but if you aren’t able, try to find a neighbour/friend/generous green soul who might donate some. It’s usually available at the garden shops as well. One thing to note is if it’s homemade (even if it isn’t), you may get some easily plucked weeds (which can then be composted!). You might also bring in some pests (insects and/or their eggs,mainly) which could prove to be more of a hassle than it’s worth in the end. Compost’s NPK content can be difficult to dial in between batches too, so it’s sometimes hard to keep a consistent profile. An excellent alternative, and my personal choice for making soil for an indoor grow is manure. I have used both steer and sheep manure instead of compost with very good results. Watch though – these manures tend to be fairly dense and have a relatively high moisture content, and so don’t promote drainage as well. They are an excellent choice though, and are usually very cheap and available.
And that’s it! Mix it all up nice and evenly, moisten (a good 4-6 L of CLEAN, chlorine-free water is usually lots), cover and let sit (also known as cooking – I use a 60 gallon drum for this) for a minimum of 1-2 weeks but preferably 3-4, mixing and turning occasionally. I like to use a kiddie pool, dump all my ingredients in, and mix it up with a rake. Saves a lot of mess, and you can usually get everything blended quite well. After mixing, I transfer it all to the 60 gallon drum and put the lid on. Every couple days I open it to refresh the air, as well lay the drum on it’s side (with the lid on, obviously) and roll it around to mix up the ingredients until the 3-4 weeks are complete. It’s important to blend very well in order to avoid ‘hot spots’ due to clumping of ingredients.
I usually grow in 3 gallon pots filled approximately 2-3 inches (5-8cm) from the top, and my plants are always happy from day 1 straight through to harvest (regular/feminized plants usually grow vegetatively for 4-6 weeks, flower for 8-10 weeks and/or autos run from 90-120 days, seed to chop). I can usually get about 20 x 3 gallon pots worth per batch, which usually lasts me for the whole year. It’s quite cost-effective at ~$30-50 per drum or close to about $3/pot. I use it to start my seedlings in as well. And obviously, you can use this mix for any plant you want to grow, not just Cannabis. I have a 4 year old Aloe plant that absolutely loves it…
I should add that during the grow I do add liquid kelp fertilizer to the irrigation water once per week, and a locally made compost tea called EPSI. once every two weeks. I also inoculate the soil with mycorrhizal fungi when planting/transplanting. These aren’t necessary if you can’t get your hands on them, but are very nice to have. Besides that though, no additional nutrients needed. Just properly pH adjusted water (6.5-7.0 pH) and a grower’s love. If you do have a deficiency (Mg is the most common I’ve run into if something does occur), topdressing the soil with the appropriate fertilizer and watering it in is all that’s required.
And remember to find the best value for your money when sourcing these ingredients as well – buying bulk is always cheaper, and bone meal, blood meal, perlite, epsom salts, and dolomitic lime can all be preserved basically indefinitely, if kept moisture free.
If these ingredients are not available to you, or you want to use something else, this is a link to a list of some alternative options. Even if you do have everything listed above, it’s worth having a look at. Just ensure whatever you decide to use provides close to the same amount of whatever nutrient you are replacing. The link is:
Also, here is a very short, but excellent article regarding these organic inputs we are focusing on in this soil mix, for anyone interested:
And, if you really want to delve deep into the very interesting science of soil microbiology and the soil food web, I highly recommend checking out this link from the brilliant Elaine Ingham:
*About using wood bark or composted-wood based-soils (like ‘The Answer’ brand I mentioned before) is that if the wood hasn’t fully decomposed, it can actually rob the soil of nitrogen to help to continue this decomposition so, make sure that your soil is fully soil without big chunks. I’ve never had an issue personally with this but, it is a thing, so be wary.*