PH Nemesis

I'm almost ready to start my first serious grow. The part that I'm most confused and worried about is PH. I've looked at a few in-depth explanations to what it is but they were to complicated and some even had chemical equations and stuff. I'm not trying to be a plant scientist or anything but most of the threads I've looked at so far have been too vague so I'm sorry if this has already been asked a million times. Please help a noob out.

I'm going to buy a PH meter, dolomite lime, ph down. I'm going to grow in FoxFarm Ocean Forest Organic soil. So here's my question. If I want to keep the ph constantly at 6.8 (or whatever is best), what do I buffer my medium at with the dolomite lime and what PH do I bring my nutrient solution or water to before adding it? And where do I need to measure the PH to ensure the most control?

And am I missing anything? Am I misunderstanding how it works? I appreciate all feedback. Thank you.

Ok check out this chart for soil grows:

View attachment 1233340

It just shows that at different pH levels, the elements the plant needs to absorb through the roots have more or less availability. For example, at a pH of 9 a plant will have major trouble trying to uptake iron and manganese from the soil. At a pH of 5 a plant will have trouble trying to uptake calcium and magnesium.

At a neutral pH (7), all of those elements are available for the plant to uptake and use easily at the levels it needs. At 7, the major elements that plants use in high amount: nitrogen, phosphorus, potassium (NPK) have high availability. And even though a pH of 7 is not optimal for iron and manganese (for example), the plant doesn't use that much iron and manganese so it still works out overall.

But in the end, the moral of the story is that a neutral pH (~7) allows a plant to uptake everything it needs at the approximate rate it can use them.

Might sound complicated but it's not if you take a little time looking at the chart.

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Forgot to add - what most people do is just check the run-off water that comes out of the bottom of the pot when feeding (or just watering if you want). If it is outside of a neutral range, you can then start adjusting the water you use to compensate. So if your run-off is coming out at 8 and you want it at 7, then pH adjust your water before you use it next time to around 6. The run-off should then start coming out closer to 7. Hope that makes sense?

Growing hydroponically has a slightly lower recommended pH range but without getting into unneeded science - the reason is the same.

IMO, you're going the right route, choosing 6.8 as the PH to shoot for, being that you're using soil. If you go 6.8, go 6.8 with your water, and your fert mix as well. Basically. try to keep everything there. You won't need to add any lime to the FF OF, because it has PH-stabilizers included, which tend to hold the soil close to 7.0(neutral). PH will drop over time, that's inevitable, which means that it wouldn't be a bad this to add a little extra lime to your soil, when transplanting to your bigger pots. Don't add any lime to the soil you'll be using for seedling, or newly-rooted clones, that's asking for trouble. The plants are really sensitive at that stage, and can easily be effected(negatively) by having a bit too much lime in the soil. After that stage, lime is fine, as the bigger plants can tolerate it better. That soil is fine as-is, so IMO, don't mess with it,(referring to lime only. I always suggest adding perlite) til later on. Alot of guys go with 6.5, which works great, as well as 6.8. I've always gone with 6.8, myself, and never had a problem. Anything in the ballpark, will work. I like 6.8, because I believe it keeps the PH from dropping sooner than 6.5 would, yet still is in a range where nutes are readily available. The choice is your's, and as long as you stay consistent, you'll be fine.

Also, get some PH Up, because most nutes drop your PH, and it'll be alot more useful than PH Down, in most cases. I've never used PH Down, personally.

I'm guessing you bought the lime as a way to raise pH? Dolomite lime is usually used outdoors to amend the local soil if it is very basic (usually a season prior to anything being grown in that soil). I'm not sure it's used very often in indoor growing because as jawbrodt pointed out - most commercial soil mixes (like FF) already contain pH buffers to be around 7 in pH.

Maybe someone will come along and prove me wrong about using dolomite lime as a pH adjuster with container growing indoors but thought I'd mention it in case you bought the lime thinking it was a good pH adjuster to use indoors with small containers and commercial soil mixes.

IMHO far too much worry is expended on pH - like all plants, MJ is widely pH tolerant.

I bung a bit of lime in my soil and that is it - I NEVER measure pH after that.

My 3 plants this year gave me 44 ounces.

But people who cant get one ounce still warn me about nute lockout, whatever that is.

It just depends - the water out of the tap where I live is over 8.5 (no idea what it really is as my pH meter doesn't go higher). And even though cannabis is fairly tolerant, if I forget to pH adjust the water before I use it I start seeing strange discolorations/browning/necrosis within 24-48 hours on the lower leaves. Even buffered nutrients seem to fall out of suspension if I don't pH adjust the water a bit first. And my plants will pretty much just stop growing as well if I don't pH this crazy water - I've tried that as well to see if they would just adjust over time but no-go.

But I agree that for most people in most situations, pH is overly fretted over. Is a pH of 8 going to really matter compared to a pH of 6? Not likely unless there are other issues going on as well. A lot like humidity levels. Are you really going to see a noticeable difference in yield between a plant vegged at 20% humidity as opposed to 40%? As long as mold isn't a problem, I doubt anyone is going to diss smoking your product because the humidity was too low under optimal during veg.

Optimal is optimal - it's just a good reference point. Not a strict rule. I get what you are saying though Spanishfly. In fact, for my soil plants I don't mess with pH at all either. I use rainwater for them and just trust that any of my commercial nutrients/soil is going to be reasonable as far as pH goes. My hydroponic plants are a different story entirely though.

My tap is about 7.0 - 7.2 the few times I've checked recently.

I did some adjusting to a batch I'm using now, got it right at about 6.5 - 6.7. I'm using baking soda and vinegar for adjustments.

I have that Milwaukee Meter, I hate it, has to be adjusted each time. I guess though for the cost and what I need to use it for it will work.

Thanks guys. I'm feeling a lot better about this.

TaoWolf said:

I'm guessing you bought the lime as a way to raise pH?

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The only thing I've bought so far is the lights.

TaoWolf said:

Maybe someone will come along and prove me wrong about using dolomite lime as a pH adjuster with container growing indoors but thought I'd mention it in case you bought the lime thinking it was a good pH adjuster to use indoors with small containers and commercial soil mixes.

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The way I understand it, dolomite lime is an amendment to the soil to help buffer the PH. Whatever that means.

pelt1 said:

My tap is about 7.0 - 7.2 the few times I've checked recently.

I did some adjusting to a batch I'm using now, got it right at about 6.5 - 6.7. I'm using baking soda and vinegar for adjustments.

I have that Milwaukee Meter, I hate it, has to be adjusted each time. I guess though for the cost and what I need to use it for it will work.

Click to expand...

Yeah I think I'm going to get a decent one.

Spanishfly said:

IMHO far too much worry is expended on pH - like all plants, MJ is widely pH tolerant.

I bung a bit of lime in my soil and that is it - I NEVER measure pH after that.

My 3 plants this year gave me 44 ounces.

But people who cant get one ounce still warn me about nute lockout, whatever that is.

Click to expand...

Ok then bruh. I liked where you were going with the pH up and pH down chemical poisoning comment in someone else's thread. I just won't worry about my pH since I'm getting quality soil and plant food. Do you think I should add any dolomite lime to FoxFarm Ocean Forest organic soil?

Not that I necessarily think it's poison or anything. Just unnecessary chemicals that might effect the flavor or potency? Actually I have no idea (lol) but if it's something that I don't really have to worry about or spend money on then I won't.

I haven't checked my PH for around 6 months now and my plants couldn't be happier.
If you go organic using soil it should buffers the PH to around 7, which is just fine.

Start with LC's mix (or subcool's supersoil that can be found in its subforum around here):


LC's Mix is great for any stage of growth. You can germ seeds in it, grow mothers in it, root clones in it as well as veg and flower in it.

LC’s Soiless Mix #1:
5 parts Canadian Spaghnam Peat or Coir or Pro-Moss
3 parts perlite
2 parts wormcastings or mushroom compost or home made compost
Powdered (NOT PELLETIZED) dolomite lime @ 2 tablespoons per gallon or 1 cup per cubic foot of the soiless mix.
...Wal-Mart now sells worm castings.

Or, if you use Pro Mix, Sunshine Mix or Fox Farm mixes...
LC's Soiless Mix #2:
6 parts Pro Mix BX or HP / Sunshine Mix (any flavor from #1 up) / Fox Farm Ocean Forest or Light Warrior
2 parts perlite
2 parts earthworm castings
Powdered (NOT PELLETIZED) dolomite lime @ 2 tablespoons per gallon or 1 cup per cubic foot of the soiless mix.
If you use a 3 qt. saucepan as “parts” in the amounts given above, it equals about 1 cu. ft. of soiless mix and you can just dump in a cup of powdered dolomite lime.
But, a "part" can be anything from a tablespoon to a five gallon bucket. Just use the same item for all of the "parts".



You will need to add some food to that.LC's Mix is great for any stage of growth. You can germ seeds in it, grow mothers in it, root clones in it as well as veg and flower in it.

LC’s Soiless Mix #1:
5 parts Canadian Spaghnam Peat or Coir or Pro-Moss
3 parts perlite
2 parts wormcastings or mushroom compost or home made compost
Powdered (NOT PELLETIZED) dolomite lime @ 2 tablespoons per gallon or 1 cup per cubic foot of the soiless mix.
...Wal-Mart now sells worm castings.

Or, if you use Pro Mix, Sunshine Mix or Fox Farm mixes...
LC's Soiless Mix #2:
6 parts Pro Mix BX or HP / Sunshine Mix (any flavor from #1 up) / Fox Farm Ocean Forest or Light Warrior
2 parts perlite
2 parts earthworm castings
Powdered (NOT PELLETIZED) dolomite lime @ 2 tablespoons per gallon or 1 cup per cubic foot of the soiless mix.
If you use a 3 qt. saucepan as “parts” in the amounts given above, it equals about 1 cu. ft. of soiless mix and you can just dump in a cup of powdered dolomite lime.
But, a "part" can be anything from a tablespoon to a five gallon bucket. Just use the same item for all of the "parts".



With that mix and using organic ferts you shouldn't have PH problems.

I did little PH adjustment using FFOF soil. The main thing is when using ferts. FF Tiger Bloom in particular makes the water WAY acidic, so whenever I fed I'd check and adjust using PH Up or Down.

obijohn said:

I did little PH adjustment using FFOF soil. The main thing is when using ferts. FF Tiger Bloom in particular makes the water WAY acidic, so whenever I fed I'd check and adjust using PH Up or Down.

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I only plan on using FoxFarm Grow Big and Big Bloom. Do you think those will my soil acidic?

Giblet said:

I only plan on using FoxFarm Grow Big and Big Bloom. Do you think those will my soil acidic?

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As long as you PH-adjust the mix before you use it, you'll be fine.

jawbrodt said:

As long as you PH-adjust the mix before you use it, you'll be fine.

Click to expand...

Ok. Will you guys comment on what Spanishfly said?

Spanishfly said:

IMHO far too much worry is expended on pH - like all plants, MJ is widely pH tolerant.

I bung a bit of lime in my soil and that is it - I NEVER measure pH after that.

My 3 plants this year gave me 44 ounces.

But people who cant get one ounce still warn me about nute lockout, whatever that is.

Click to expand...

Giblet said:

Ok. Will you guys comment on what Spanishfly said?

Click to expand...

Basically, if you use a decent soil, and don't feed them with something that has a whacked-out PH, there's not much to worry about. Add a little lime to be extra-safe, feed and water them with PH around 6.5, and you won't have to worry about PH. The main reason soil goes acidic, is from keeping it wet for a long time. It'll decompose and could go acidic, given certain conditions. The other reason, is from guys assuming they are watering/feeding with correct PH, when in fact, it's way high or way low. Get that right, and you'll be good to go.

Thanks man.

First of all I fail for not rereading my thread and noticing that TaoWolf had already answered my latest question. lol. But anyway, I was just reading about pH meters and decent ones are kind of expensive and the whole calibration thing seems like such a hassal! I'm now thinking I'll just mix in some dolomite lime into my mix and be done with pH for good. I'll only add it to my big pots after transplanting. Any recommendations on how much to add to 3 gallon pots? Not even really 3 gallons because they have this weird inward cone design at the bottom for aerating the roots.

View attachment 1241844

New Patent Pending cone technology, promotes vigorous root growth, while using less soil.

Plant Warrior growing containers provide added oxygen to the soil environment.

Patent Pending design allows oxygen to be drawn through the bottom of container promoting, healthy, strong roots.

Sturdy injection molded containers.

Available in four sizes, 1 gallon, 2 gallon, 3 gallon and 5 gallon.

Reusable and easy to clean.

Click to expand...

I'd also appreciate opinions on these pots too. It'll actually work out well because I have 4 pots and I'm getting the 10 gallon bag of FoxFarm Ocean Forest.