Maintaining a soil pH of 6.5

jjf1978 · Dec 5, 2009

When trying to maintain a soil pH of 6.5 what do you adjust your feeding pH to and your plain watering / molasses water pH to? I guess it's all based on the pH of your soil dry (something I have not been able to determined). What indicators tell you if the soil pH is getting too acidic? I've tested runoff but it always seems to come out acidic even if I water with neutral 7.0 pH water. I don't think runoff tests are accurate because the water is washing the nutrients out of the soil concentrated into the runoff - so the pH of the runoff is always going to be more acidic then the actual soil right?

:wall:

Boneman · Dec 5, 2009

Just maintain a 6.5 of what you water your plants with. If you start measuring the run off, you will end up chasing a number.

Heads Up · Dec 5, 2009

I agree with boneman. After I mix my additives into my water, I ph it to 6.5 or darn close and use it immediately, I do not let it sit around for a couple of days so the ph can change. I'm just starting my third week of flowering and I ph my water to 6.4, after about week four I'll ph it to 6.3 and keep it there for the rest of the grow. I've noticed from my previous grows my soil tends to get alkaline towards the end of the grow hence the lowering of my ph when flowering.

jjf1978 · Dec 5, 2009

Boneman said:
Just maintain a 6.5 of what you water your plants with. If you start measuring the run off, you will end up chasing a number.

Yes that is exactly what was happening, just started chasing a number based off guesses and I think I screwed up one of my plants, not horribly but still...

Thanks for your advice Bone! I"ll make sure to keep my watering pH at 6.5 - just need a digital pH meter now, I hate trying to figure out a number looking at the pH color chart.

Heads Up said:
I agree with boneman. After I mix my additives into my water, I ph it to 6.5 or darn close and use it immediately, I do not let it sit around for a couple of days so the ph can change. I'm just starting my third week of flowering and I ph my water to 6.4, after about week four I'll ph it to 6.3 and keep it there for the rest of the grow. I've noticed from my previous grows my soil tends to get alkaline towards the end of the grow hence the lowering of my ph when flowering.

How did you determine that your soil went alkaline?

Heads Up · Dec 5, 2009

By using a soil ph tester. I can't really call it alkaline, that was my bad, it was verging on being alkaline, a touch above seven.

Mechman60 · Jul 26, 2022

Ok here goes. Tomorrow is 8 weeks for the girls. 3 Autos and one mystery seed. I'm watering with only 6.5 molasses water. I may have a little lockout so it may cause an influx of nutes that are locked out. Probably no biggie.
Here's a few before pics from today.

Jjgrow420 · Jul 28, 2022

Mechman60 said:
Ok here goes. Tomorrow is 8 weeks for the girls. 3 Autos and one mystery seed. I'm watering with only 6.5 molasses water. I may have a little lockout so it may cause an influx of nutes that are locked out. Probably no biggie.
Here's a few before pics from today.

#1 this thread is ancient.
Second, .... Watering with molasses water? What does that mean ? If you're using molasses every watering you are doing more harm then good. Molasses causes your medium to become acidic if it's building up in it, you can also cause a explosion of microbes, then a mass die off which can lead to bad bacteria taking over (will smell bad) Is that straight peat? Your medium might be very acidic, and if it's already showing problems they're just going to get worse fast especially with the molasses.
Also keeping your measuring instruments on top of the pot is measuring the temp and rh% on the top of the pot and is not a good indication of the actual environment Gl

TankHankerous · Jul 28, 2022

I have a tote of soil I'm preparing for my next transplant. I amended my promix hp with perlite, earth worm castings and dr earths ferts. By the time I was done with it I took a slurry test my ph of the medium was around 5. I added some aluminum sulfate to raise the ph a couple weeks ago and let it cook. Now I did a slurry test today and it read 5.8-6.2. Is this sufficient for promix and regular NYC tap water? I will not be ph-ing water due to general laziness but I will let it sit out and dechlorinate for 24 hours!

PadawanWarrior · Jul 28, 2022

Jjgrow420 said:
#1 this thread is ancient.
Second, .... Watering with molasses water? What does that mean ? If you're using molasses every watering you are doing more harm then good. Molasses causes your medium to become acidic if it's building up in it, you can also cause a explosion of microbes, then a mass die off which can lead to bad bacteria taking over (will smell bad) Is that straight peat? Your medium might be very acidic, and if it's already showing problems they're just going to get worse fast especially with the molasses.
Also keeping your measuring instruments on top of the pot is measuring the temp and rh% on the top of the pot and is not a good indication of the actual environment Gl

What bad bacteria do you think will take over?

PadawanWarrior · Jul 28, 2022

Mechman60 said:
Ok here goes. Tomorrow is 8 weeks for the girls. 3 Autos and one mystery seed. I'm watering with only 6.5 molasses water. I may have a little lockout so it may cause an influx of nutes that are locked out. Probably no biggie.
Here's a few before pics from today.

They look a little hungry to me. What's your medium and nutrients you're using? JJ was right that molasses can lower soil pH. Not about the bad bacteria thing though. How much are you using?

Mechman60 · Jul 28, 2022

Jjgrow420 said:
#1 this thread is ancient.
Second, .... Watering with molasses water? What does that mean ? If you're using molasses every watering you are doing more harm then good. Molasses causes your medium to become acidic if it's building up in it, you can also cause a explosion of microbes, then a mass die off which can lead to bad bacteria taking over (will smell bad) Is that straight peat? Your medium might be very acidic, and if it's already showing problems they're just going to get worse fast especially with the molasses.
Also keeping your measuring instruments on top of the pot is measuring the temp and rh% on the top of the pot and is not a good indication of the actual environment Gl

I realize theses things but thanks. I've been using molasses for years just not on weed.
BTW they look great today. Smells sweet also. I think the reason that what you say is true but not with rural AZ water. It's about 7.2 but very difficult to move.
Also I screwed da pooch on my soil. It's about 60% compost and not enough perlite the rest is manure.
The soil looks like peat because I top dressed because I'm doing some fungi fly control. It's diatomaceous earth food grade. Worked on my last grow. But it went better. Guess ya can't be cheap about it all. Used what was on hand. I find old posts handy too.lol

Mechman60 · Jul 28, 2022

Mechman60 said:
I realize theses things but thanks. I've been using molasses for years just not on weed.
BTW they look great today. Smells sweet also. I think the reason that what you say is true but not with rural AZ water. It's about 7.2 but very difficult to move.
Also I screwed da pooch on my soil. It's about 60% compost and not enough perlite the rest is manure.
The soil looks like peat because I top dressed because I'm doing some fungi fly control. It's diatomaceous earth food grade. Worked on my last grow. But it went better. Guess ya can't be cheap about it all. Used what was on hand. I find old posts handy too.lol

I velcroed the meter to the wall 1/2 way up. Thanks

Jjgrow420 · Jul 28, 2022

PadawanWarrior said:
What bad bacteria do you think will take over?

If you get a microbe crash it can make the soil anaerobic. Anaerobic bacteria produces phytotoxins. (If) there's ample food (eg molasses every watering) the population increases too quickly and basically it's like walking down the streets in India for the microbes not to mention they don't like an acidic environment. They crash, and they're little bodies decay. It's legit. Your soil will start to smell like a rotten fart. Maybe it's a 'worst case' scenario but why not give the poster the best chance to not have a bad situation get any worse. Literally just listened to Jeff lowensfeld (author : teaming with microbes) say exactly what I said in an interview with Tad Hussey (kis organics). Not looking for a fight man.

Jjgrow420 · Jul 28, 2022

Great read I do recommend it btw.

Hiphophippo · Jul 28, 2022

I try and build my soil to buffer the ph itself so I don’t worry about the ph of my water or my soil using the right amounts of silica products and lime and the right nutrients and amendments will keep everything right also using Epsom salts and keeping your microbe life strong and healthy and you’ll forget all about ph sorry for the run on sentence I was using voice to text

PadawanWarrior · Jul 28, 2022

Jjgrow420 said:
If you get a microbe crash it can make the soil anaerobic. Anaerobic bacteria produces phytotoxins. (If) there's ample food (eg molasses every watering) the population increases too quickly and basically it's like walking down the streets in India for the microbes not to mention they don't like an acidic environment. They crash, and they're little bodies decay. It's legit. Your soil will start to smell like a rotten fart. Maybe it's a 'worst case' scenario but why not give the poster the best chance to not have a bad situation get any worse. Literally just listened to Jeff lowensfeld (author : teaming with microbes) say exactly what I said in an interview with Tad Hussey (kis organics). Not looking for a fight man.

That's a new one to me. I know about the population crash stuff, but turning it anaerobic I've never heard. Do you have a link to the video?

Jjgrow420 · Jul 28, 2022

Mechman60 said:
I realize theses things but thanks. I've been using molasses for years just not on weed.
BTW they look great today. Smells sweet also. I think the reason that what you say is true but not with rural AZ water. It's about 7.2 but very difficult to move.
Also I screwed da pooch on my soil. It's about 60% compost and not enough perlite the rest is manure.
The soil looks like peat because I top dressed because I'm doing some fungi fly control. It's diatomaceous earth food grade. Worked on my last grow. But it went better. Guess ya can't be cheap about it all. Used what was on hand. I find old posts handy too.lol

No worries. I use black strap as well. Less is more. Although there are some elements in black strap (specifically black strap) it's not enough to be considered a 'feed'. It feeds the food web... Or the soil itself. It doesn't make the plant sweeter.

Jjgrow420 · Jul 28, 2022

PadawanWarrior said:
That's a new one to me. I know about the population crash stuff, but turning it anaerobic I've never heard. Do you have a link to the video?

It's Tad's podcast.

Jjgrow420 · Jul 28, 2022

PadawanWarrior said:
That's a new one to me. I know about the population crash stuff, but turning it anaerobic I've never heard. Do you have a link to the video?

If you brew a tea, then remove the airstone and leave it for a day does it not turn anaerobic? Same idea. Those bacteria are present always. They just can't take hold because well think of it like a party and all the good bacteria are occupying the container so the bad ones can't get in ..there's no room. If it crashes and they all die well the anaerobic bacteria now have a: space and b: a food source.

Billy the Mountain · Jul 28, 2022

Some informative episodes for sure

Cannabis Cultivation and Science Podcast

This is the podcast where we bring leading experts from the horticulture and gardening industry and find out the latest information and research for cannabis cultivation. Forget the marketing hype from bottled nutrient companies, everything on this show is based in science and research. If you...

www.kisorganics.com

Maintaining a soil pH of 6.5

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