Down and Dirty Super Soil for Organic Marijuana

organic marijuana

There are lots of recipes for Sub Cool’s Super Soil on the net. Why is super soil important? If you want to grow organic marijuana but don’t want to fuss too much with organic fertilizers and whatnot during the growing season you can use super soil as a one time, take care of everything solution.

The idea is to create a super soil that is packed with all the things that organic marijuana needs during it’s life cycle. You put this soil in the bottom of plant pots (or if you’re growing outside in the ground you put it into the bottom of the hole), then cover the rest with regular, un-manipulated soil. The plant begins growing in regular soil, but as the roots develop they start finding the super soil and take off.

The idea with growing any plant, including marijuana, is to replicate as closely as possible the optimal environment. Set the plant up for success and then let it do it’s thing. Sub Cool has developed a great recipe over the years, as have some other growers. Google “subcool super soil” and you’ll get a good grounding in what’s going on.

The problem that I had with the recipes were that they used terms like “4 large bags of Brand X Soil”, without saying how big Brand X’s large bag actually was. If you don’t live where the grower lives, especially if you’re living in a different country, you’re not going to get the same brand of soil or the same size bags. I’ve re-written and re-jigged the recipe to be in parts. That way you can make any size batch you want.

The other problem I had was that I had to read and re-read a lot of recipes to get a clear understanding of what was going on. Hopefully my description will make things clearer to a newbie.

Here’s the first thing to understand. You’re going to start with a base soil. Some of this base soil will be made into super soil, and some will be put aside as base soil. When you fill your pots or your holes the super soil will go on the bottom and the regular base soil will go on top. Some people put in half super soil and half base, and other put in 1/3 super soil and 2/3 base. You need base on top because young plants and clones will get burned if you plant them right into the super soil.

The base soil is usually store bought potting soil. There are different brands and different types. Do some research on the web and see what growers in your area prefer. Where I live we can’t buy a lot of the brands I see recommended in the forums. The common brand around here, Sunshine Mix, gets mixed reviews. Try to check out the ingredients, although in some countries and with some brands you may not get to see much.

One thing you really want in the soil you buy is mycorrhizae. This is a fungus that bonds to the roots of your plants in a symbiotic relationship. The plant gives the fungus carbohydrates like glucose and sucrose, and in return the fungus improves the roots’ ability to absord water and nutrients. I was able to find potting soil with mycorrhizae in it pretty easily – hopefully you will too. Don’t be scared by warnings that there is fungi in the soil – that’s what you want.

You also need aged compost. Aged compost is compost that won’t burn your plants. New compost, while great in some applications, can steal nitrogen from your plants while completing the composting process. You can buy aged compost in bags, or you can use your own (which is what I did). Aged compost should be dark, crumbly and be able to sift through a 1/2 inch screen.

Organic worm castings are also required. Again, worms eat my garbage, so I have organic worm castings. If you don’t have a worm composting system you can buy worm castings. You can also start your own worm composting project. organic marijuana

You need vermiculite or perlite as well. These improve the drainage in the soil by lightening it and making it resitant to compacting. They also improve air movement through the soil.

These are the big ingredients for your super soil (or my down and dirty version of it). Remember, you’re going to put at least half, and possibly 2/3s of the base soil to the side for the top level of your pots/holes, so you probably need to buy more than what I put in the recipe.

Next come the nutrients. You need blood meal, rock phosphate, alfalfa meal, kelp meal, green sand and bone meal, You need azomite, epsom salts and dolomitic lime. Blood meal is essentially dried blood, and is a great source of nitrogen (it can also be used to deter rabbits). Rock phosphate is a source of phosphorus and calcium. Alfalfa meal is naturally high in nitrogen and benefits soil microorganisms by helping them convert soil nutrients into soluable forms more available to plants. It also contains the naturally occuring groth hormone, Triacontanol, which boosts the growth rates of seedlings. Kelp meal is a good source of nitrogen and potassium. It also contains minerals, amino acids, and trace amounts of other micronutrients. Greensand is a good organic source of potash along with iron, magnesium, silica and as many as 30 other trace minerals. Bone meal is a slow release source of phosphorus. Bat guano provides high levels of phosphorus and nitrogen

You also need azomite, which is a source of over 70 trace minerals. Epsom salts provide magnesium. Dolomitic lime also provides magnesium and lowers PH (which may or may not be required).

So, here’s the recipe I used:

5 parts base soil material
1 part aged compost
1 part worm castings (organic)
2 parts vermiculite or perlite
1/8 – 1/4 part each of:
blood meal
rock phosphate
alfalfa meal
kelp meal
grean sand
bone meal
bat guano

1/16 to 1/8 part:
azomite
epsom salts
dolomitic lime

Mixing is a challenge, but not too hard. I used a cement mixer and a couple of sheets of plywood. You can use child’s pool or a tarp or a clean concrete floor. The important thing is to mix everything really well. If you’re mixing by hand don’t just throw the ingredients on top of each other. Spread the base soil out first, and then spread the ingredients evenly across the top of it. Turn it over carefully and thoroughly to make sure everything gets mixed in. organic marijuana

Once you’ve done that you put the super soil into a container. I used a couple garbage cans. Add 1 – 2 parts water, cover, and let stand for a month outside. Let the microbes in the soil flourish. Check your ph before using it, but remember that nutrients in organic soil are more accessible to plants, so ph isn’t as critical as it is in hyrdoponics.


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This blog talks about different ways of growing marijuana. Growing marijuana may be illegal where you live, and if it is I don't recommend that you break the law. Also, don't do damage to other peoples' property while cultivating cannabis. Instead, if you're going to do it, cultivate something special that you can share with your friends and that you can be proud of.