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The business end of a cannabis plant may be above ground, but it’s down in the earth where all the magic happens. And because weed ain’t no ordinary houseplant, it needs something a little richer than just potting soil if it’s to produce decent bud.
Therefore, growers have two choices: either buy a ready-made soil specially designed for cannabis plant growth or generate their own homemade super soil.
What Is A Super Soil?
The term super soil gets thrown about a lot when cannabis growers get together, despite lacking a clear definition. Essentially, it refers to any soil recipe or mix containing the ideal ingredients for growing cannabis.
Different growers have their own soil recipes, but the best soil for cannabis usually consists of a base mix plus a load of amendments like guano, bone meal and worm castings. Ultimately, the goal is to provide cannabis plants with a mix that contains all the essential macronutrients and a broad spread of micronutrients.
More specifically, cannabis soils need to provide plants with the three major plant nutrients: nitrogen, potassium and phosphorus. Additional micronutrients like copper, iron, manganese and zinc can then be introduced using a range of weird and wonderful ingredients.
Just as importantly, a cannabis super soil must have the right texture, consistency, aeration and water retention properties. Additional amendments are therefore often thrown into the mix to improve the structure of the soil, ensuring it remains light and airy with good drainage while still holding a significant amount of water.
When the balance is right, your plants’ roots should have enough to drink without becoming waterlogged and starved of oxygen. Meanwhile, an abundance of nutrients and optimal pH makes the rest of the growing season an absolute doddle, as there’s really nothing more that needs doing apart from watering and harvesting when the time comes.
Key Ingredients And Amendments
Getting the base mix right is fundamental to providing the right soil for your cannabis plants. This will make up about a quarter to half of your final soil mix and should be well aerated, permeable and slightly acidic.
To make things easy, you could just pick up any organic soil from your local garden centre that matches the above description. Some more expensive products contain other ingredients like coco coir, peat moss and worm castings, so it’s worth splashing out a bit to get the perfect base for your soil.
Alternatively, you could make the base yourself. To do so, you’ll need to mix up some compost, organic material and aeration amendments in roughly equal measure. The compost you can either buy or make from kitchen scraps and garden waste. Bear in mind, though, that it can take over a year for this material to decompose and be ready to use, so you’ll need to plan well in advance.
Coco coir, perlite and vermiculite are all ideal ingredients to add to the base mix, as they help with water retention and drainage, creating the perfect soil texture for your cannabis plants.
Once the base is ready, you’ll need to start mixing in amendments to provide your plants with all the macronutrients and micronutrients they will need. Worm castings, for instance, provide nitrogen while also introducing loads of helpful bacteria, which help make nutrients more readily available for plants’ roots.
Bat guano, meanwhile, is a great source of both nitrogen and phosphorous, while wood ash and kelp meal provide potassium. Greensand is another excellent addition, as it slowly releases micronutrients like iron and silicon.
Creating the best soil for your cannabis plants also means establishing a thriving fungal community, which can be achieved by adding mycorrhizal amendments. These fungi form mutually beneficial relationships with plants’ roots and help to distribute nutrients through the soil.
Cannabis Soil Recipe 1
If you don’t have much composting experience, it may be best to start with a simple beginner’s mix. This means buying your base straight from a garden centre rather than making it yourself. Any neutral potting mix will do, but if you can get your hands on something that contains coco coir, perlite or guano, you’ll have a head start.
Next, add a generous helping of worm castings, equalling about 20 per cent of the total volume of soil you want to make. Extra bat guano should also be added, totalling five per cent of the final volume.
About a quarter of a teaspoon of mycorrhizal powder per gallon of soil should be plenty to kick-start that all-important fungal population and create a high-quality living soil. A quarter of a cup of kelp meal for every five gallons of soil, meanwhile, will provide a potassium boost.
|Method||– Combine worm castings and potting mix (20% of total volume)|
– Add bat guano (5% of the total volume)
– Add 1/4 teaspoon of mycorrhizal powder per gallon of soil
– Add 1/4 cup help meal per 5 gallons of soil
Cannabis Soil Recipe 2
Rather than using potting soil, we’re going to take things up a notch by making our own base mix this time. To do so, you’ll want to combine one part coco coir, one part perlite, one part vermiculite and roughly 1.5 parts organic compost. This last ingredient can be bought from a garden centre or made at home, bearing in mind that a compost pile can take anywhere from a few months to a couple of years to be ready to use.
Be sure to mix the base well to achieve the right consistency before adding in the micronutrient amendments. For every five gallons of soil you end up with, mix in one-third of a cup of bat guano, kelp meal and alfalfa meal – the latter of which provides an extra nitrogen kick.
Depending on your compost’s pH, adding some dolomite lime as an acidity regulator may be necessary. This handy ingredient contains magnesium and calcium and will raise the pH of an acidic soil to bring it into the optimal range for cannabis plants. Generally, about a quarter to a third of a cup of dolomite lime per five gallons of soil does the trick, but you may need to adjust this amount after consulting your pH meter.
About half a teaspoon of mycorrhizal powder per gallon will get the whole soil mix teaming with fungal life, ensuring express delivery of vital nutrients to plants’ roots.
At this stage, it’s worth mentioning that a super soil like this is way too rich for cannabis seeds or young seedlings, which should be started off in neutral soil and transplanted into your homemade mix once they have three or four nodes. Even larger plants can get burnt by such a hot mix, so be sure to give your soil several good soakings over a number of days to cool it off before putting anything in it.
|Method||– Combine 1 part coco coir, perlite and vermiculite with 1.5 parts organic compost|
– Ensure the base is mixed well
– Mix 1/3 cup of guano, kelp meal and alfalfa respectively in soil mix
– Add 1/3 or 1/4 of dolomite lime depending on your ph
– Add 1/2 teaspoon mycorrhizal powder
Cannabis Soil Recipe 3
This next soil mix for cannabis plants was first shared by legendary breeder Dave Bowman, better known as Subcool. This recipe first popularised the term ‘super soil’ and continues to be used by weed growers worldwide.
The base mix consists of eight large (ten-gallon) bags of high-quality organic potting soil that contains coco fibre and mycorrhizae. To this, add 25 to 50 pounds of worm castings, five pounds of steamed bone meal (a great source of phosphorus) and five pounds of bat guano.
A further five pounds of blood meal provides a nitrogen boost, while three pounds of rock phosphate enhances the phosphorus content. A third of a cup of Epson salts helps to break down the nutrients in the soil gradually, and half a cup of dolomite lime regulates the pH of the entire mix.
A further half-cup of azomite provides cannabis plants with all the trace elements they may need, while two tablespoons of humic acid powder boost microbial activity and improve nutrient uptake.
This hot mix needs about one to two months to ‘cook’ before it can receive any plants. During this period, you’ll need to place your soil in a sealed container, opening it once a day to mix it all up and check that it’s still moist. Water your mix if it gets too dry, but don’t allow it to become waterlogged.
This process will stimulate the microbes and allow all the ingredients to dissolve so that the nutrients become available for use by your cannabis plants.
Steamed bone meal
|Method||– Combine 25-50 lbs of worm castings, 5 lbs steamed bone meal and 5lbs of bat guano with potting soil|
– Add 5 lbs of blood meal and 3 lbs to rock phosphorate
– Mix in 1/3 cup of epsom salts
– Add 1/2 cup dolomite lime
– Mix in 1/2 cup azomite
– Add 2 tablespoons humic acid
– Add mixture to sealed container/s
– Leave mixture for 1-month minimum to combine
– Open up mixture once a day to mix and ensure it remains moist, add some water if not