Hey DGC! I’ve heard a lot of chatter around the crew lately about making your own soil. I’m not a college trained “soil expert” or anything like that, but I’ve been making my own mixes for a while now so I thought I’d share some of what I’ve learned. My goal is to present what I’ve learned in an understandable way so please forgive me if I oversimplify things or say things that are downright incorrect in order to get my general points across.
I also want to specifically acknowledge Jeremy from www.BuildASoil.com for helping start me on this path.
His blog posts about making your own soil and studying the soil recipes for sale on his site were what finally gave me the courage to take the plunge and start making my own mixes. He was also on the show to talk with Dude and Scotty (Episode 39 back in May 2014) and has appeared on other growing podcasts a few times as well.
If you are out there Jeremy, Thanks for all you do my friend, and please come back on the show! We have lots of new organic soil growers in the crew and we could use your expertise!
I also want to quickly say that its my belief that if you are growing your plants with love and care there is no wrong way to do it. I have nothing but love for all my grow sisters and brothers out there growing in hydro, coco, organic, synthetic or whatever else you might be doing. Whatever style you choose, as long as you do it with love and respect, growing cannabis is one of the best things you could choose to do with your time, and I applaud you for doing it. Bring the dank however you want, JUST BRING IT. 😛
That said… I have fallen in love with soil… 🙂
What goes into a good mix? I’ve begun to think of my soil mixes in four distinct parts, with each part playing a critical role in creating the end product:
- Base Mix– Provides a structure for the roots to hang on to and acts as a sponge, holding air, water, nutrition, and biology within.
- Organic Nutrients- Provide the majority of the nutrition to the plant.
- Minerals- Provide some nutrition (especially calcium and micro nutrients) to the plant but they also play a key role in soil texture, soil pH, and many other processes that are key to healthy plants
- Biology– Bacteria, fungi, archaea, nematodes and other kinds of creatures who make their home in soil are ESSENTIAL to creating a healthy soil environment. Together they make up a food web of creatures that process, store, and make the nutrition in your soil available to your plants. Biology connects the other components together and creates a living system you and your plant can take advantage of for better growth and plant health.
In other words:
The Base Mix acts like a sponge for Organic Nutrients and Minerals, and serves as an environment for the Biology needed to tie the whole mix together and turn it into a healthy soil.
Now lets break each part down a bit further.
To me, a good base mix is all about a nice balanced texture. A good soil mix will hold a decent amount of water and air while providing lots of fluffy surface area for nutrients, minerals and biology to cling on to and colonize. Good soil needs to be able to hold lots of water, but also lots of air, so finding the right balance between the two is key. If your mix is too heavy it will be muddy and will stay soggy too long. If its too light and doesn’t hold enough water it will dry out too quickly. There may be a small amount of nutrition provided by the base mix, but generally most of the nutrition is coming from elsewhere.
Good Common Base Mix ingredients include: Coco, Peat, Compost, Worm castings, Pumice, Rice hulls, Bio char, and lava rock (compost and worm castings provide some nutrition)
The “meat and potatoes” of the mix. Organic nutrients make up the majority of the nutrition your plant will be receiving from the soil. Theses are the building blocks your plant uses to grow bigger and to create the beautiful flowers we are after. For this reason, I think its worth the extra time and energy to source the best materials you can get your hands on. Its also very important to note that its always better to error on the side of adding too little of something than it is to add too much. When growing in organic soil, once you put something into the soil, its very difficult to get it back out. You can always add nutrition later on down the line if you think your plant needs a boost so its best to start off light.
I highly recommend starting out with a very light amount of nutrients in the soil and making plans to top dress or use some liquid fertilizer later on if you need it. Trying to cram too much nutrition into your soil is a recipe for trouble and almost always ends up hurting the quality of your final product.
Good Common Organic Nutrients Include: Neem seed meal (aka neem cake, left pic), Kelp meal (center pic), alfalfa meal, crab meal (right pic), and other organically grown seed and plant based “meals”
Minerals are mined rock and clay materials. They provide a lot of the trace elements required by our plants and the majority of the calcium. Calcium is used by your plant to make new tissue, including buds so you want to make sure its available. Agricultural mineral products containing calcium are pretty common, but some become available to the plant at different rates. It seems best to apply a few different calcium sources to insure there is always something available when the plant needs it.
When it comes to trace elements, I’ve found the best approach to be a broad one. Plants use trace minerals in such tiny amounts, its probably impossible to predetermine exactly how much of things like Molybdenum or Boron you are actually going to need. A more realistic approach is to use a “rock dust” product that contains a wide variety of minerals, each in small amounts. This ensures there is a little bit of everything there that the plant can access as it needs, but not too much of any given thing as to cause toxicity or other problems.
Good Common Calcium Mineral products include: Oyster shell flour (left pic), Gypsum (center pic), calcium carbonate, and cal phos (contains phosphorus as well)
Good Common Rock Dust products include: Azomite, Cascade Mineral mix (right pic), rock dust local brix blend basalt
To bring the rest of your components together to create a living soil, you are going to need creatures and critters. Your goal is to create a living ecosystem within your soil. Nature has taught us that diversity is a key component in any healthy ecosystem. You cant just have one kind of critter running around in your soil, you need a complex system of creatures all serving their individual roles to create a balanced ecosystem. I suggest using several different sources of microbes and soil biology to ensure a diverse ecosystem. I like to use some “wild sources” as well as some good “lab grown” sources. These creatures serve such a vast variety of functions, its best to have as much diversity as possible to get the most benefit. The best way to maintain a large and diverse population of beneficial critters, and to keep this system running and healthy for the long term, is reapply them on a regular basis as your grow progresses.
Good “wild sources” for soil biology include: compost, worm castings, backyard soil
Fantastic “lab grown sources” for soil biology include: Recharge! and Mammoth P
Thanks for reading!
Check out Making Soil with Soup Part Two, where I will share and discuss some of the soil recipes I have tried and will explain how to mix and “cook” your soil so it is ready for planting.