Howdy my esteemed homeskillets. That whole using lime in growing containers dynamic is pretty important. Container soil, especially cannabis targeted soils, have huge ratios of organic matter vs. mineral matter. For this article “mineral matter” will be what I call all the other elements (in mineral form) in the soil the plant and microlife need and use to live and propagate, that aren’t technically organic. Like Azomite, SRP, greensand, and many others.
If you are growing in the ground, even in raised beds with high ratios of organic matter in the raised beds, the soil underneath is rich in mineral elements. Way lower ratios of organic matter. Why is this important? Because when organic matter is breaking down it tends to shoot the pH downwards, fast. As most of you know, this is bad, on several levels for your living roots; and the bacterial dominant soil life.
Today’s article revolves around the word BUFFERING. My favorite way to buffer is by using lime in growing containers, composted right into the soil. Specifically, dolomite lime, for some good reasons I will lay out below. But there are many ways to buffer your soil, so let’s have a little overview, shall we?
Using Lime in Growing Containers – the Art of Buffering
Let’s start out with some general info about lime. What we are really talking about here is calcium (Ca); which is a metal, FYI. Calcium carbonate is the form we will be dealing mostly with today. Calcium from bones, sea shells, and the hard shells (and exoskeletons) of many creatures, like crabs, shrimp, crickets, mites, beetles, etc. Limestone itself is mostly calcium carbonate. There are forms of calcium carbonate too, found in limestone. The two most prevalent forms of calcium carbonate in limestone are Calcite, and Aragonite.
Calcium in your soil tends to raise the pH. This is normally a great thing, but like anything else, using too much can bone you hard. Using lime (Ca) in growing containers, bottom line, is very simple if you are using living soil. Here’s some of the rules…
- Lime (Ca) must be composted into your soil before living roots can be in that soil. It takes about 30 days to compost it in.
- Try and secure a good source for Dolomite Lime, a special lime that is a true buffer, and the lime you will want to use when growing in containers. I will tell you more about it below.
- Prilled or pelletized dolomite lime is great stuff, but it MUST say FAST ACTING on the label. This is actually my favorite lime of choice to use.
- Lime additions aren’t the only way to give your plants pH balanced soil. You can use things like wood ash, diatomaceous earth (DE), and even tree bark as well. DE must be agricultural or food grade only.
- Having good amounts of calcium (lime) in your water is also an excellent way to keep all the soil life including your plants extremely happy and healthy.
Ratios and Benchmarks When Using Lime in Growing Containers
For dolomite lime I try and target my ratios to be about 1 to 2 tablespoons per gallon of soil mix. Using something like wood ashes, you need to be very careful because even a small overdose will become deadly fast. I use more like 1 teaspoon of wood ash per gallon of soil mix.
Avoid hydrated lime, it’s just way too crazy in my experience. I have seen it used successfully when growers using bagged soil mix and an organic liquid feeding regiment. The hydrated lime counters the hard pH dive caused by the liquid organic nutrients quite well. They used ½ cup hydrated lime per 9 gallons (1.5 cubic feet) of soil mix.
Using things like oyster shell as a pH balancer, I would go with ½ to 1 cup per 9 gallons of soil. You can also help your pH stay balanced by adding some bark mulch, shredded is best. Just add about 2 gallons of shredded bark to 9 gallons of soil mix. All of these additions above require that you compost them into the soil, even the bark mulch.
Using Lime in Growing Containers, Dolomite Lime, The King
Using most of the amendments that will balance your pH require a little dialing in, as far as the ratios go. Dolomite lime is easy peasy man. Dolomite lime is a TRUE BUFFER. Which simply means it will direct the pH towards neutral (7.0 pH) no matter if it is higher or lower to begin with. That my green friends, is just pure awesomeness! Other pH adjusting additions can be cruel. The more you add the higher your pH rises. Wood ashes and hydrated lime are both notorious for disaster, unless extreme care is used dialing in your ratios.
Another great way to bring in calcium for not only buffering pH, but as a nutrient, along with magnesium (Mg)—another element cannabis plants really love—is by using dolomite lime with your water. If you took something like rain water, or distilled water, or reverse osmosis filtered water, and bubbled some dolomite lime (like 1/8th teaspoon per gallon of water) for 24 hours. You would have water about 60 PPM at 7.0 pH that will help buffer the soil. It will also feed the soil life and the plants. Use the water every time you water.
Just remove the air-stone after 24 hrs. let it sit for about 5 minutes and pour the water off the top. Avoid pouring any sludge. Boom! Beautiful cannabis water. Using lime in growing containers isn’t limited to the soil. The water is a perfect delivery system. In nature most groundwater is rich in Ca and Mg.
Important Update on Using Arrowhead Water
There I was, smoking a little hashish, when I read an email from a TLO fan named, “Chunky NY.” He tells me his Arrowhead spring water is registering 200+ PPM! My first thought was that his TDS meter was all caddywhompus and in error. Then, I broke out a bottle of Arrowhead and checked it—WTF? I registered a PPM value of 210 PPM. That shocked me, bigtime!
The last time I checked the PPM and the pH of Arrowhead spring water, it was like 11 years ago, at least. Back then Arrowhead registered more like 55 PPM on my TDS meter. Okay, 200 PPM is around 4x too much PPM indeed. It’s still alright for sprouts because they will be out of their little containers fairly quickly. So, the excess salts won’t have time to reach toxic levels.
So, here’s the fix: 2 parts distilled water to 1 part Arrowhead spring water. This brings my Arrowhead water down to about 65 PPM; which is all good. Reverse osmosis filtered water would also work if no distilled is available. 55 to 65 PPM is a good range if using Arrowhead on sprouts or freshly rooted clones. Thanks for the heads-up Chunky NY—good lookin’ out. 😎👍
There You Have It Amigos
Well, I hoped you enjoyed today’s article about using lime in growing containers. If using something as a pH raising amendment like oyster shell crushed, etc., set out to dial in your benchmark ratios so it becomes a simple task in the future. Under-guess ratios off the bat if unsure, you can always add more later. If your plants are suffering from a pH dive, they look yellowish, chlorotic, especially at the growing tips. Also, growth is stunted.
Here’s another article for your reading enjoyment if you choose, Mulching Your Cannabis Plants for Microbes – Skunk Magazine. See ya all back here next Tuesday at SKUNK baybee. L8r G8rs.
- REv 😊
I'm The Rev, and I have been with SKUNK for about a decade now. I hail from Southern California, spent mucho time in Northern California, and now reside in Southern Oregon; always coastal. I am an all natural style cannabis grower and I have written a couple books on the subject - check out True Living Organics 2nd Edition on Amazon - I have been growing for over 45 years, and I have been breeding cannabis for over 30 years. Check out kingdomorganicseeds.com to see some exotic selections. Growing connoisseur cannabis is what I teach mostly, growing it in living soil without using liquid organic nutrients to feed the plant. I am also a highly skilled synthetics grower, hydroponics, aeroponics, DWC/SWC/NFT, Ebb and Flow, and soilless, but I cringe when smoking synthetic grown herbs, so for the last 15 years or so I preach the artisan style of all natural growing, specializing in container growing. Cheers and welcome aboard.