Soil pH problem or not?

Hey RIU,

Hopefully you guys can help me out I've been reading a lot and before I decided this post so let me give you the details

Growing SFV OG in FFHappy Frog ( contains domolite lime which should help buffer pH correct?)

Only nutrients being used is FF Grow Big 1/2 strength. which is 1.5tsps/gallon

I am watering with TAP water which test high in pH above 7.5 but with Grow Big it drops its down to 6.8-7.

But if i water by itself no nutes shouldnt the soil buffer the water? I let the water sit out for couple days to evap Chlorine.

So my first that is Ca def as noted here
https://www.rollitup.org/marijuana-plant-problems/488004-guide-nutrient-deficiency-toxicity.html

If you take a look at the first pic looks almost exactly like what I have but than again Tap water High in pH normally means its high in Calcium Carbonate?

But Ca does not get locked out unless your under 6.5pH.

Sooo yea any input greatly appreciated. NPK values for grow big 6-4-4 incase you didnt know. Plant is a clone about 8" in height. 400wHPS humidity 41 temps around 78-83.

about 1 week previously to that she was in 6 inch pot with Ocean Forest...

jojo2002 said:

Hey RIU,

Hopefully you guys can help me out I've been reading a lot and before I decided this post so let me give you the details

Growing SFV OG in FFHappy Frog ( contains domolite lime which should help buffer pH correct?)

Only nutrients being used is FF Grow Big 1/2 strength. which is 1.5tsps/gallon

I am watering with TAP water which test high in pH above 7.5 but with Grow Big it drops its down to 6.8-7.

But if i water by itself no nutes shouldnt the soil buffer the water? I let the water sit out for couple days to evap Chlorine.

So my first that is Ca def as noted here
https://www.rollitup.org/marijuana-plant-problems/488004-guide-nutrient-deficiency-toxicity.html

If you take a look at the first pic looks almost exactly like what I have but than again Tap water High in pH normally means its high in Calcium Carbonate?

But Ca does not get locked out unless your under 6.5pH.

Sooo yea any input greatly appreciated. NPK values for grow big 6-4-4 incase you didnt know. Plant is a clone about 8" in height. 400wHPS humidity 41 temps around 78-83.

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Yes, the soil will buffer the water sitting in contact with it to that of the soil. That's not a deficiency yet. If the soil is properly limed, the ideal soil pH should be 6.8, but it just isn't that crical. Values of as low as 6.4 or high as 7.2 can be tolerated by a lot of strains pretty damn well. You have more than enough Ca, in fact you may have an over abundance, and lock out Mg.

So you think I might have a lock out of Mg? I dont think i have to much nutes or the plant would show signs of nute burn on the tips which i dont have at all most of the leaves are nice and green with the exception of 1-2 fan leaves showing those spots. So jack how do you think its Mg being locked out if so I can I correct it?

bkb I have pH down and ill adjust my tap so its closer to soil pH. Thanks.

That's all well and good, but the soil is gonna buffer that pH to it's pH as long as that lime is present, and it would take a good long time to leach that out. More than 6 months, but it can also be safely supplemented at about 3 months by topdressing.

Jack your referring to the the domolite in the soil not being effective after 6 months correct? My question is to reduce the Ca if that is infact causing the the lock of Mg if so what can I do either supplement the Mg or reduce the Ca ?

Just don't feed 'em for a bit. Don't add any Ca. either

Havent gave them any nutes some leaves seem to turning over so underside is showing is this due to Mg lockout? should i buy some epsom and foilar feed until soil adjusts?

This may help...found it on another thread on RIU.

jojo2002 said:

Havent gave them any nutes some leaves seem to turning over so underside is showing is this due to Mg lockout? should i buy some epsom and foilar feed until soil adjusts?

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Plants are getting hungry, foliar feed with a 1/2 str nutes high in N with trace elements, then start feeding the plants thru the roots by watering the nutes in.

jojo2002 said:

Jack your referring to the the domolite in the soil not being effective after 6 months correct? My question is to reduce the Ca if that is infact causing the the lock of Mg if so what can I do either supplement the Mg or reduce the Ca ?

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That's not what I'm saying at all. The dolomite in the soil is gonna be effective for AT LEAST 6 months or more. It has to leech out by dissolving in water!!! Some forms of Ca are more readily assimilated by plants, so if the dolomite isn't providing it, then by all means supplement a form that can be used by the plant. If the dolomite is there at the start, then it SHOULD provide all the needed Mg and Ca.

Gotcha thanks Ive been i just flushed them some leaves are showing Mg def.... I went to hydro shop today the owner told me that the water should be ph'd at 6 for soil when watering... any input.

Example:
If the pH of the soil is 6.8 (or whatever value), and you water with a solution that has a pH value of 7.5, as the water sits in contact with the soil, the calcium carbonate in the soil will bring the water's pH down to 6.8 (or whatever value the soil has). It's NOT important what the pH of your watering solution is, or what the pH of the run off is. As the watering solution sits in contact with the soil, the soil itself will change the pH of whatever goes into it to that pH value of the soil. It is not an immediate thing. It takes a few minutes for this to happen. This is known as "buffering". A buffer is a substance that has a certain pH value, and resists any change to that value. The pH up or down you buy in the stores are great for TEMPORARILY altering the pH value, but the pH will inevitably return to its original value unless it is buffered. In soil that has been properly limed, pH is never an issue. In hydroponics, where there IS NO BUFFER, pH is critical, and can swing radically. Chasing pH in hydroponics can be a real son of a bitch.
Now it IS a good idea to get the watering solution as close to 6.8 as possible to avoid shocking the roots. I have no proof that the roots can be shocked in this manner, after all acid rain is prevalent on the eastern seaboard, yet we see no real detriment to the vegetation, because the soil CHANGES the pH of the rain to the pH of the soil. But just in case, I would probably correct the pH of whatever you are watering with, no sense taking chances!!
The way I see it, most of the people who are really concerned with pH are either hydro growers, or are getting the info from hydro growers, and it has evolved and spread into a generally accepted truth, usually by people who know how to use a pH meter, but really have no grasp of pH and how buffers work.

Does any of this make sense? It took me FOREVER to get my mind around pH and how it works. If I haven't made this clear, please tell me and I'll try and explain it again to help you make some sense of it!!

I'm a bio major I totally understand buffers and pH im no botanist though, i was somewhat confused because of plants showing Mg deficiency and the soil contains Domolite lime which is made up of CaMg(CO3)2 and I was feeding very lightly Grow Big which also contains trace elements with the exception of Ca. So the pH was what lead me to believe that Mg might be locked out. Now my water is hard which means it contains Calcium carbonate now that I think about it I might have to just use RO water to help minimize the Ca so the Mg does not get locked out... Thanks for the help..

Cool, if you have a good grasp on the pH concept, then you are way more ahead of the game than 99% out there. Look around, you'll see that pH is one of the most misunderstood concepts out there!!!
Lock out can occur from many causes, and many symptoms of the deficiencies mimic each other. For example, P Ca, and Mg are very interrelated. an over abundance of one can lock out the other. Also, an Mg def looks a lot like a P deficiency in how it manifests itself. Same with Ca, and K. It is hard to just sit and look at the plant and say for sure that it's one or the other. Visual diagnostics has to be taken with the nutritional regimen in mind, and all of the other environmental factors as well.
If you understand pH, then you KNOW that a properly buffered soil will not change over the relatively short period of a grow, and that pHing the water going in will not affect how the soil adjusts pH.

Yea totally if a "buffer" allowed for pH to fluctuate at long periods of time it wouldn't be a buffer just like us humans we have Bicarbonate buffer system that maintains pH in our blood with acid and base imbalances some of use would have issues it didnt work and some people do have these issues just like some soils dont have good buffer systems. No matter what goes in or buffer system should take care it all the elements are there. Now my theory is though we should if we want to preserve the buffer system in the soil we should have the water we feed pretty close to the pH of the soil just so the degradation of the buffer system is slower depending on the length of the grow or replaced if degradation is quick.

Absolutely! I agree with that, if only to prevent shock. But it isn't an absolute necessity!! Watering with a pH of 8 isn't gonna change anything immediately!
Newbies need to know this because I see more newbies obsessing over pH in soil like they are gonna kill off the crop in one swell foop!

Jack Harer said:

That's not what I'm saying at all. The dolomite in the soil is gonna be effective for AT LEAST 6 months or more. It has to leech out by dissolving in water!!! Some forms of Ca are more readily assimilated by plants, so if the dolomite isn't providing it, then by all means supplement a form that can be used by the plant. If the dolomite is there at the start, then it SHOULD provide all the needed Mg and Ca.

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Jack
You are totally correct except for one thing. It seems that FF just adds enough dolomite or oyster shell flour or whatever to make it on the label and that's about it.

Seems to be enough to last for about 6 weeks and gone. Ever notice how so many run into pH problems in the middle of flower with FF mixes? 3-4 weeks veg, a few weeks in flower and the pH plummets.

If they put the right amount in the mix to begin with, it would certainly last 6 months. If

Wet

I am of the same opinion on FF. I can't stand the shit. I see WAAAY too many people having issues with just that!!! As for the running into issues early to mid flower, I find that it is almost invariably a Mg issue! Many strains devour Mg and Ca in flower, Sats in particular (or Sat doms) But most people are SO hung up on pH in soil that the first thing they say is it's pH issue, and given the fact that over 80% of the people out there have no clue what pH really is or how it works, they start pHing the water going in and further screw up and compound a problem. I have yet to see a true pH related lock out with any soils except one that has not been limed and is composed of totally inert media.
As with any soil, FF needs to be tested before the grow starts or before you put plants into it. If the pH is low, as it invariably will be, add lime to the entire mix, then test another sample. Keep at this in baby steps until you get to 6.8 (or as close as possible). Then pH will not be an issue. FF claims to use oyster shell in their mix. Whatever is there will remain there, because you'd have to dissolve all the oystershell before the pH will start swinging. It's usually low, and unless more lime or oystershell is added, the pH will always be low. FF is almost ALWAYS low, but not low enough to cause a lock out. In soil, pH has to be pretty damn far out of whack to affect the nutrient uptake.