PH help


Active Member
So I'm am new to growing and this whole ph thing. I have been tracking my soil ph with a soil ph meter and my water and nutrient solution with ph strips and everything was fine until I switched to flowering.
I would normally make my nute solution and check the ph. If it was within 6.1-6.9 I would leave it as is. I would water my plants and a while later I would check my soil ph with the soil ph meter. Throughout all of veg it was consistently within the range and I wouldn't need to do anything.
The other day i switched to flowering and gave them their first feeding. Soil was at 6.8 in all 4 plants. I made my solution with tested at about 6.25-6.5 (using strips). After feeding all 4 plants my soil ph meter was reading the soil at 4.0! I never had such a drastic change. The next day it was up to 6.1 so I don't know if my meter malfunctioned or what happened. So now I got a water ph meter/pen and want to test my soil ph with out feeding again to get a base. What is the best way to do this? Do I water with plain ph'd water until I have runoff and just test that to get my soil ph? Do I have to recalculate anything depending on the ph of the water I water with? Any help is appreciated
Hi Rad, welcome to the forum!
The problem is in your tools. That soil probe is not actually able to measure the soil pH... it is simply an approximation.

The actual soil pH that concerns us all is called the base pH of the soil... or the pH that it reverts back to when it is dry. You can't measure that with that probe. You have to measure base pH in a slurry test, measured under a vacuum. Most commercial soils have buffers in them to set the base pH up near 6.8, and you really shouldnt mess with that.

The reason we adjust pH is so that our nutes can free themselves of the salt chemical bonds they are in so that they can be stored in a bottle and set on the shelves for a long period of time. These chemical compounds are designed to break apart within a certain range of pH.... soil nutrients are set to the 6.2-6.8 range and hydro nutes are set to 5.5-6.1. As long as you adjust your mixes to within these ranges, the nutes will become "mobile" in the solution and will be able to be taken up into the plants.
Many of the elements inside the nutes are not mobile at the same pH.... some are more mobile at the lower end of the scale and some at the middle or high end. Here is where the soil buffers and the base pH come in. If you water at a pH that is at the low end of the soil range, such as 6.3 pH, the vast majority of the elements inside the nutes become mobile at that pH. When you apply this fluid to the soil, at that moment, the soil, the fluid and everything inbetween has no choice but to assume the pH of the fluid that you saturate the soil with. At that moment, the pH of your container is 6.3 pH. Then, as the plant uses up the water, the water table inside that container begins to fall and the top part of the soil begins to dry out. The close it gets to dry, the closer it gets to the base pH, no longer being influenced by the pH adjusted fluid below. In this dryer part of the container, the pH rises, moving through the entire pH range right up to where the base pH is set and during that excursion through the pH range, all of the elements inside of the nute package become mobile in their turn.
It is a great system, and one that was put in place for you by the soil manufacturers. You don't have to do anything but water at the correct pH, and let the soil do its thing. It really isn't as complicated as you are trying to make it.
Thanks Emilya. I appreciate you taking time to help me out. Thanks for the explanation, I understand it a little more now. I know I have something wrong going on in my setup and I am just trying to learn how to dial it in. A few of my leaves are getting some brown spots and not looking too good. Not sure if it's a ph problem, lockout due to ph, or just a cal or mag def. Here is a pic.


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hi rad

post up a pic of the whole plant. a couple random leaves does not give a proper picture of the plant's health.
could be looking at old damage you have already grown past.
So the plant that leaf came off of is in the top right of the first picture. I was also told that my new growth is a little too light. I thought it looked pretty good but now I don't know. Any input on that?
You might be right about it being old growth the plant grew past already because it did come off the lowest and oldest of the nodes on the plant
the stuff lower down could have been a PK issue.
suspect you've got past it by now though. would encourage other input as that is really just a guess.

the second to last pic has me bothered.
it's looking to be more predatory than nute issue to me. really hope not.

i'd get a loupe and go all over the leaves, especially the underside.
possible early mite or other predator damage.

edit : might see a tiny bit of mag or calcium issue on the older stuff. doesn't look widespread.

let's tag @Emilya for a look. she's way better at this than i am
I thought the same thing about second to last photo as well. Started looking into whether it is mites. Only seems to be on the one plant and the one leaf. I looked at it with a loupe and don't see anything moving. Not sure if these are eggs though or not, they do look like it to me. Don't see anything on any other leaf, top or bottom. I took a picture through the loupe. Not sure if you can see anything though.
Nothing on the back side of the same leaf. Checked it quite well. Absolutely nothing. Will I see these things moving?
I was also told that my new growth is a little too light. I thought it looked pretty good but now I don't know. Any input on that?

New growth is always a lighter green, and that looks normal to me anyway (maybe someone else think different, but depends where you heard it too ;) as lots and lots of bad info out there on other places on the internet). Also base things off the new growth and not the old growth as most "issues/problems" the old leaves never change once it is "fixed".
So i removed the leaf that had the damage and "eggs" and checked the rest of the plants and leaves and don't see anything similar anywhere. Should I just Minister the situation for now or get some neem oil or insecticidal soap right away. What is best to be used? And does it matter that I am in flowering already?
if early flower hit them with the neem right now. there is no such thing as just one leaf.

neem degrades and should not be present at harvest if you act fast. you can also bud wash at harvest to remove residue.
Ya I only just switched to flower this past monday so I am as early as it gets. I know from what I read not to use neem oil on buds. And spray top and bottoms of plants I'm guessing right.
neem is 100% organic.
something to consider for the different methods of consuming cannabis.
So I got a ph pen today and did a feeding. My water has a ph of 7.0 and when I added my nutrients it was at 5.8, so I raised it to 6.5 with ph up. I watered the plant and collected the earliest runoff I could. It read at a ph of 4.4. Assuming the other 3 plants should be at about the same ph, I mixed the solution and raised the ph a bit higher to 6.8-6.9. I water the other 3 plants one by one and each of their runoff was at a ph of 4.9. So now, do i just keep feeding with a solution of 6.8-6.9 until my runoff raises back into the right range and then stabilize my solution ph to that? Am I reading all the info I collected correctly?
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