We’ve already published two articles about soil for marijuana growing and this is the third.
In the previous articles we covered:
- Sourcing soil that’s properly made, clean, free of sticks, excess filler, stones, pests, and diseases.
- Adding 5-15% extra coarse perlite to soil for marijuana growing because almost all commercial soils are too dense.
- Finding out from the manufacturer everything that’s in the soil when you buy it.
- Packing soil when first transplanting your marijuana plants and watering tips.
- Weighing your potted plants when the soil is dry so you know how much water to use when watering.
Some readers asked me about my statement that if you water a pot so much that water runs out the bottom you’ve watered too much.
It’s true that when water runs out the bottom you get these benefits:
- Oxygenation is spread from top to bottom of your root ball.
- Stagnant nutrients are flushed out, helping to prevent root zone nutrients excess.
- Spaces inside the root zone are rearranged so roots can spread more easily.
- Roots are cleansed… and nutrients, oxygen, and moisture are delivered to them.
The problem is you don’t want to waterlog your root zone.
Even with proper drainage at the bottom of the pot, and the right amount of perlite, you can still end up with a waterlogged root zone.
What often happens is that the soil at the bottom of the pot is too moist and the soil higher up isn’t moist enough.
Over the years I’ve learned to water until only a small trickle of water comes out of the bottom of the pot.
If I have suspicions that my root zone is toxic due to a nutrients build-up or for other reasons, I’ll use zero parts per million reverse osmosis water with a flushing solution like Flawless Finish and no other additives.
In those cases, when I have to flush the root zone, I’ll be chill with more than a trickle of water coming out of the bottom of the pot.
When I suspect my root zone is too wet, I crank up my dehumidifier to make the grow room air drier than usual, around 45% humidity, until I see the plants have pushed through the excess root zone water.
I urge you to use drip irrigation systems. But if you hand-water your soil, be sure to use a watering pot rather than a wide-mouth dispenser.
I’ve seen people watering with 5-gallon containers that dump a massive amount of water all in one place at the top of the root zone.
It’s better to water slowly and carefully so you’re wetting the entire root zone evenly.
However, let me contradict myself! In some cases I want to water the root zone selectively so the water leads my roots where I want them to go.
For example when I’ve just transplanted into new soil for marijuana growing and my roots at the top of the root ball are in older soil, I want to lead those roots to the bottom of the pot.
What I do is I water from the bottom by putting the pots in trays filled with nutrients water so the water wicks up rather than pours down from the top.
If I transplanted from a small pot to a much larger pot with lots of space around the diameter of the existing root ball, I water from the top of the pot, but only around the sides.
This encourages the roots to develop towards the new soil in the sides of the pots.
The last things I want to discuss about soil for marijuana growing have to do with nutrition and soil pH.
Most of the commercial soils I purchase such as Fox Farm Ocean Forest have a surprisingly substantial starter fertilizer charge built in that can last throughout grow phase and maybe even into the first couple weeks of bloom phase.
I realize that some soil companies also make fertilizers and they tell you to supplement with fertilizers starting early in grow phase.
My experience is that using base nutrients while your soil still has an on-board fertilizer charge can overload your plants, stunt root growth, and create root zone toxicity.
What I add during grow phase if the soil has existing nutrients already in it when I bought it are root zone beneficial microbes such as Voodoo Juice, Piranha, and Tarantula, along with Microbial Munch to feed them.
I might also add reduced doses of B-52 B vitamin booster, which has the added benefit of an N-P-K dose.
I make sure when I’m growing in soil to use organic base nutrients, Advanced Nutrients SensiZym (which breaks down organic substances), beneficial microbes boosters and the carbos that feed them (such as Voodoo Juice and Microbial Munch), and Rhino Skin, which adds potassium silicate that strengthens plants.
Because soil for marijuana growing can have dicey root zone pH due to the manufacturer not using enough lime or because of bad fertilizers and water, I’ve sometimes resorted to a soil pH meter.
After buying several soil pH meters and discovering they mostly suck, here’s the one I found most reliable.
I also note the time a fellow grower made the mistake of buying Scotts Miracle-Gro soil and had rare marijuana plants that he couldn’t easily transplant out of that shit soil.
The Scotts Miracle Gro soil pH was so off that nothing worked until he started using Advanced Nutrients pH Perfect base nutrients in the soil.
He alternated feedings between a dose 35-45% of what Advanced Nutrients recommends, with a dose of pure reverse osmosis water.
The pH Perfect base nutrients restored pH balance to the soil and the crop problems leveled off and gradually receded so the dude had a decent harvest.
Soil for marijuana growing isn’t a perfect root zone material like rockwool, coco coir, deep water culture, or other inert and/or pure hydroponics.
You can’t control soil feeding, pH, and watering anywhere near as well as you can control those factors in hydroponics marijuana growing.
However, if you choose to use soil for marijuana growing, we’re sure our three articles on this topic have helped you get the most out of your choice.