HELP! Soil grow Runoff pH seems too Low

[VespatheKid]

Hey All, I’ve got a Black Harlequin hybrid strain (CBD Harlequin x Black Domina from Sensi Seeds) growing in FoxFarm soil amended with some FF seed starter soil in week 4 of flowering in a 10gal. smartpot. Using a HLG 100 R Spec LED with temps in the low 70s day/high 60s at night. Keeping RH at 50% avg. Using FF nutrients at half recommended doses once a week. I’ve always been pHing my water and nutrients going in at the 6.5 +/- range but wasn’t good at getting good runoff until 2 months ago. Now I’m getting 15-20% runoff with every watering once a week.

The issue is my runoff has stayed in the 5-5.5pH range (in the light “Orange” color wise, I’m using drops to measure) and a bit lower when I first started measuring the runoff. (I’m guessing the low pH was from my lack of runoff initially?)

Since then I’ve been UPing the pH of the water/nutes to the 7 range and the Orange is getting a bit lighter but no Yellow (6-7pH). I even did a light flush about a month ago to see if that would get things moving.

The plant appears generally healthy outside of the blood-red stems on the fan leaves (appeared on my last grow too on two different strains, I think it’s an effect of the LEDs?). And a touch of brown spots on one fan leaf (see photo). I’ve also finished my defoliation and kept things leafy up top as a precaution.

My Question is should I keep the water/nute pH at 7 range until the runoff moves to the “Yellow” 6-7 range? Can this take months to change?

Or should I go back to the generally recommend 6.5 range on the water/nutes going in and not worry as much about the runoff unless things get worse?

Thanks.


——

Follow my grow on Bud!

[Mr.furley]

From the sounds of it you have a potassium and phosphorus problem which gives a drop in pH within the root Zone.

The time is right for it.

[Bluey]

If you are 100% that you are getting accurate run off tests then up your pH in to bring it up....if you're not 100% then it's a gamble on what to do. Give it a good flush with your nute mix at 7pH. Although your in soil I'm guessing there's little to nothing left in its tank nute wise. The leaves on the lower buds struggling look way too glossy to me and very smooth edges too.

[RetiredGuy]

I’ve had exactly the same problem when using fox farm soil (Happy Frog/ Oceans Forest). I had to do a lot of flushing to get the runoff pH back up in range and suffered deficiencies due to it. Other people have reported the same. That is why I am switching to Stonington Blend from Coast of Maine for my next grow.

[Bluey]

You're growing under quite a good LED which have a tendency to bring out cal/mag and other deficiencies as well...keep flushing with nutes plus additives. If you have an EC meter aim for over 1.6 above your base water number

[VespatheKid]

Many of you have spoken of a “good flush”. How much runoff should I be aiming for? Right now I’m watering with FF nutes once a week 3.5gal with about 18% avg runoff. Should I also add additional cal/mag to the nute mix?

[Bluey]

You don't need runoff in soil, preferably none, but you'd give it a good flush to correct issues at your roots, eg too low or high pH. Measure the runoff as it first comes out of the bottom, not midway or a bit from all of it. That will give you the best indication of what is going on at the roots and correct from there.

[VespatheKid]

Thanks for the advice. I have been sampling right at first runoff. Here’s are recent pics of the pH sample ( photo in orange is what’s coming out) if that helps to clarify.
To give it a good flush, do I just give like another gallon or two of water with nutes along with the regular watering and get rid of the runoff?

[Bluey]

So what's the score? 6.5ish? If so I'd say it's good. If it is low just up your pH the equivalent on what went in and flush. It doesn't look too low to me.
Edit. My nutes have a colouring agent in them so beware of that.

[Bluey]

There is a great article written by an experienced grower and regular contributor here called 'A tale of Two pH Meters" Look it up and have a good read of it and you'll likely end up getting yourself an Apera pH60 or P60....it's a great read

[Mollisol]

Have you considered a digital PH meter? It makes things easier.

[VespatheKid]

A digital meter is not in the budget right now but appreciate the thought. I believe I’m reading the color to pH number on the guide correctly so that’s not an issue unless someone thinks I’m way off on this.
To recap, the H2O and nutes going into the soil look between 6.5-7pH or so (photo above with the color guide) to try an up the pH at the root level. The first runoff pH in the second picture is a bright orange which looks between 5-5.5pH.

I’m now trying to get clear how to address this issue. Would it make sense to continue to keep the pH closer to 7 (or slightly higher?) going in - then to flush:
I’m actually not clear what flush means.
Should I add another gallon or 2 of water to my intake with my regular nutes and remove all runoff? Would it also make sense to add additional cal/mag with the usual FF nutes too?
thanks.

[Bluey]

https://www.growweedeasy.com/?s=Flush

[Mollisol]

This is the meter I use. Hard to go wrong for $12.00.
https://a.co/d/f18hFgA.

Problem with test tube /reagent ph testers is you can move it a point either way by the way you hold it in your hand. I don't think you are getting accurate readings.

[VespatheKid]

You're growing under quite a good LED which have a tendency to bring out cal/mag and other deficiencies as well...keep flushing with nutes plus additives. If you have an EC meter aim for over 1.6 above your base water number

Bluey thank you for walking me through this. I’m dealing with some cognitive issues, so even your simple reminders are helpful. And thanks for everyones feedback. I researched the deficiencies under LEDs issues, had not heard about that, so that was helpful. I don’t have an EC meter so I’ll investigate that too. I’m going to get that $12 ph pen (I thought I had to spend over $100 which is why I held off - thanks for the assist Mollisol ), I’ll add some cal/mag with my flush too according to this article. As I’m adding up the symptoms: low run-off ph, red stems on upper leaves, some new very light brown spots on upper leaves, darker green leaves (I believe), some new light brown tips with some clawing, and the possibility of the LED causing deficiency I’ll flush with the FF nutes and supplements incl cal/mag until I get over 6.2 using the $12 pen and see what happens in the next few weeks. Thanks again all!😊

[VespatheKid]

Lastly, a gardener friend said they have a soil pH tester kit (not a pen) I could borrow. I’m also wondering if it’s worth cutting a small hole towards the bottom side of my smartpot and extracting a little soil to test too or if the pH in the runoff will give me the same results?