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.
If you haven’t read it already, I highly recommend you start with Part 1: Soil Basics. Here in part 2 we will talk about how to plan your mix, and how to go about mixing and preparing your soil for planting.
As you read, you might start to think, “Wow Soup, this sound like kinda a lot of work…” and well my friends let me be the first to tell you, Yes, indeed it is lot of work and it requires a lot of planning. But let me also tell you that the benefits are huge!
You will work hard studying, planing your mix, and tracking down the best ingredients available in your area, but you will also learn more about plant nutrition than buying a bagged soil could ever teach you. You will spend some time measuring out amendments and get a little sweaty mixing up soil, but you won’t have to stand around mixing nutes into your water, checking it with meters and pretending you are some sort of lab chemist every time you need to water your plants. When you take the time to build a quality soil, most of the hard work is done in advance, and you’ve got a solid team of microbes watching your back for the rest of your grow.
Nothing against folks who like measuring nutes and being nutrient chemists, but I’ve learned its not for me. I’m a dirt kind of guy, and I enjoy the mixing, the shoveling and all the other associated dirtiness. 🙂
Ok, lets talk soil!
Planning Your Recipe
In Part 1, we broke down our soil mix into 4 parts: Base Mix, Organic Nutrients, Minerals, and Biology. Now lets break down each component and talk about how to use these concepts to put together an ingredients list for your mix.
The base mix is the foundation of your soil. You want it to hold a good amount of water but don’t want it to be too heavy and muddy. Fluffy, spongy consistency is what you are after. Your base mix makes up most of the overall soil volume, so figure out how many total cubic feet of soil you will need and make that much base mix. A good base mix usually consists of 3 roughly equal parts:
1 part Starting material: An organic base substance that acts like a sponge. Coco and peat moss are the most commonly used but there are other options out there.
1 part Aeration material: Keeps your soil texture nice and fluffy and improves drainage. Perlite is popular, but not the best option for a long term soil mix. It eventually breaks down to dust that will compact your soil. Pumice is a great alternative and is very similar to perlite, except it is much tougher and doesn’t easily crush. Other good options include rice hulls and lava rock.
1 part Compost material: The magic substance that turns your pile of ingredients into soil. Using just worm castings works, but worm castings and good compost works even better. The more sources of compost you use, the more diverse and robust your soil food web will be.
The organic nutrients are where your plant gets most of its nutrition. This is where your plant gets the Nitrogen, Phosphorus, Potassium, and Micro-nutrients it needs to grow and thrive. The goal here is to cover all the essentials, but to not put too much of anything. Its tempting to go crazy adding lots of nutrition, but the truth is, what your plant really wants is BALANCED nutrition. You can always add to your mix later with topdressing or liquid feeding if you need it. Once you put something into the soil its in there for good. It is best to start light and add more nutrition later on in the grow if needed. REMEMBER: Using less is almost always better. You can always add nutrition later if you need to!
-You are shooting for a good balance of NPK and Micro-Nutrients.
-Most of the ingredients I use have fairly low NPK (less than 5%). If you are using something with a higher NPK, keep in mind you will want to use a lot less.
-Some soil amendments provide more than one nutrient. Crab meal (4-3-0), for example, provides a good amount of both nitrogen AND phosphorus, so make sure you account for that while planing your mix.
-A good place to start is around ½ cup to 1 cup of each N, P and K focused ingredient per cubic foot of soil, assuming you aren’t using anything super strong.
–A good rule of thumb is about 1 ½ to 4 cups of total organic nutrients per cubic foot of base mix.
Minerals provide most of the calcium and micro nutrients your plants need. They also serve many other roles like stabilizing pH and helping build good soil texture.
-Cannabis plants use lots of calcium so its a good idea to have a few different sources of calcium to make sure there is always some available.
-Rock dusts and kelp are both rich in micro nutrients so I like to make sure I always have both in my mix.
-A good rule of thumb is around 1-4 cups of minerals and rock dust per cubic foot of base mix.
Biology is what turns your pile of dry ingredients into a living soil. The goal is to create a diverse ecosystem. This means getting lots of different sources of life to ensure this diversity, and re-inoculating regularly to maintain it.
-You will get a good amount of biology from your worm castings and compost in your base mix
-You also want to get yourself some RECHARGE from Scotty Real!
-Having things like Recharge, Mammoth P and compost teas that you can water in and re-inoculate your soil with on a regular basis is essential to this style of growing.
-Compost is a good start but the more diverse your soil food web is, the more effective it will be. Keep adding life to your soil as often as you can!
Lets Get Mixing!
Before you start, go through your recipe and double check that you have enough of everything. Mixing soil by hand is a decent amount of physical labor, but I’ve come to really enjoy it. I honestly find it really relaxing and meditative. Smoke a joint, put on some music and enjoy the process!
Once you’ve decided on a recipe and have gathered your ingredients, its time to get dirty!
There are lots of different ways to mix up your soil, so consider your situation and space available when deciding the best way for you to do your mixing.
My preferred mixing method requires a thick tarp, a rake, and a shovel. Its a bit of a work out, but it allows me to mix up a good amount of soil inside my grow area without making too much of a mess. Buy a new, clean tarp to use for this purpose if you choose to mix things up this way. Get the thickest tarp you can find so it will last you a while. Note I am using a flat tipped shovel and we are using the rake points up so you don’t rip your new tarp to shreds. Its not a bad idea to get a bigger tarp than you think you need so you can double it up, especially if you are mixing in your grow area like I often do.
I start by mixing up my Base Mix. I dump my Starting material, Aeration material and Compost material out on my tarp and use the rake upside down to spread the ingredients out and to start mixing them together. (Remember: points up or you will rip your tarp!) You can use the shovel to help mix or lift up a corner of the tarp and use it to roll the pile of ingredients around to mix them up. If you are mixing a large batch, it can be easier to do half the base mix at a time. Try to get the base mix fairly well mixed before you proceed but you will be doing plenty more mixing so it doesn’t have to be perfect at this point.
Once you are satisfied, add up how many total cubic feet of base mix you’ve got and start measuring out your Organic Nutrients and Minerals.
Its a good idea to wear some sort of breathing protection at this point. Many soil amendments are harmful to inhale, so wear protection and save your lungs for inhaling more important things.
No idea if these are adequate breathing protection, but they are better than nothing. This 10-pack was at the dollar store, so there is really no excuse for not wearing one. If you can afford it, I would pick up something that provides even better protection. Protect your lungs!
Be careful about how you handle and mix amendments. You can keep things relatively clean if you are careful, but its very easy to get dust everywhere if you are sloppy or careless.
I like to make a measured pile of each ingredient before I mix it into my base mix. Laying everything out before you add it to the base mix helps insure you don’t forget anything and allows you to take a look at your recipe before you finalize it.
This is your last chance to make any changes or adjustments before you mix everything in. Its also a good chance to take a picture or write down your final recipe so you remember what you did.
Once I have all my ingredients laid out, I use the rake (points up!) to spread the pile of base mix into a flat sheet. Then I use the shovel to scoop up each ingredient pile and spread it out carefully across the top of the base mix, layering one ingredient after the next.
Once everything is layered up on top of the base mix, I go to town mixing with the shovel and the rake. I like to use the rake to flatten out a sheet of soil, then grab each corner of the tarp and fold it over, pulling the soil with it and mixing it into a pile again. Rake it flat, fold it over, then repeat.
It starts to feel like kneading a giant pile of bread dough. Mix until you have an even consistency and all your amendments are all mixed in. Its a lot of labor but smoke a bit and put on some music and just enjoy the mixing process. You’ll be done before you know it. At this point, the mix looks like soil, but its not quite done yet!
“Cooking” Your Soil
Imagine you are making a stew. You cut up all your veggies, toss in the meat and potatoes, add all your spices to the broth, but you still have just a pot full of soggy ingredients, not a stew. The cooking process is what merges all the individual components together into something new and tasty.
Well your soil needs to undergo a similar process. The good news is, you don’t have to be a master chef because we are going to let the soil Biology do all the cooking! Just like cooking stew on the stove brings all the ingredients and flavors together, the soil food web “cooks” the Organic Nutrients and Minerals together with the Base mix and turns it into something tasty and nutritious for your plants.
“Cooking” soil = adding soil biology and waiting for them to digest your ingredients into a plant available form.
This naturally occurring process is essential, and this is what turns your big pile of ingredients into real soil!
-There should already be lots of microbes and soil life in the Compost materials we added to the base mix. This means the cooking process has already started, you just need to give the soil food web time to complete the process.
-The amount of time you need to wait for your microbes to “cook” your soil depends on what ingredients you used and how much life there is in your soil to do the “cooking”. Some mixes take very little time to cook, some can take a lot longer. It depends on what amendments were used.
-If you plant in your mix too soon, the cooking process will still be going on in your pot! This will likely cause nutrient imbalances in your plants. The cooking process also generates surprising amounts of heat, which can damage your roots.
-Adding more life and diversity (Recharge!) to your soil food web as its cooking will help move the process along.
-Keep your soil moist but not soggy during the cooking process to keep the soil food web functioning at full capacity. Check on your cooking soil regularly and add water if it starts to dry out.
-Keep your soil in a large pile or container and cover it up with a lid or a tarp to keep pests out while it undergoes the cooking process. Leaving your soil exposed while it cooks is like inviting fungus gnats to move in! Cover it up!
-4-6 weeks seems to be a safe amount of time to wait for all the amendments to be fully broken down and to become plant available.
This soil was mixed then lightly watered with Recharge before I shoveled it into a plastic tub for cooking and storage. A month later, the soil is teaming with microbes and all the ingredients have fully cooked. This soil is so full of life you can clearly see mycelium spreading across the surface. Recharge ladies and gents… its good stuff!
Alright you are probably hungry from all that cooking talk, so now seems like a good point for a break. 🙂
Go get yourself a tasty snack and stay tuned for Making Soil with Soup: Part 3, Recipes and Why You Should Create Your Own.
Thanks for reading!