DWC PH dropping question

[FreezerBoy]

in flowering period ph always drops in dwc

Not true. Flowering or not, pH can rise, fall or remain flat.

 

[BudMasterzero]

Well the PH dropping issue and ppm rising issue yet again rears its head. So my plan of action so far, add my regular tap water (after bubbled it is around 6.7) and add til the ph stabilizes.

once again thank to all the brains who can help with this problem!

 

[Stagetek]

That will depend on how much swing you have. Be careful of how much water you add; if your original grow medium (i.e. the rockwool cube sitting in a netpot full of hydroton) gets saturated, you can end up with rot. If you want to try and control the swing with added water alone, you may need to do a partial res change, or elevating your buckets above the floor in order to get more headroom in the buckets.

On a related note; the following thread (post 568) has a post regarding water levels in buckets in relation to the development of thick cord roots, caused by an air gap between medium and nutrients, and their effect on the plants:

https://www.icmag.com/ic/showthread.php?p=4248008&highlight=%22cord+roots%22#post4248008

 

[Inspired333]

Rough rule of thumb is:

• pH drop with nute strength increase; back off on nutes
• pH rise with nute strength decrease; plants want more nutes
• solution in res drops with pH and nute strength stable; it's a good thing

I have a similar issue but while pH drops, solution strength (EC, PPM, TDS) stays stable. In my 2 current grows, at least, there is no difference in pH swing regardless of whether or not I use a pH buffered version of base nutes. A few years back I had similar issues using tap water; so I doubt that RO water is my cause. Strains are dissimilar as well.Like you, my plants look healthy; but I'm constantly waiting for the other shoe to drop.

Are you using any silica products? Some have postulated that potassium silicate can cause pH swings.

Wish that were so; both my flowering RDWC grows have pH dropping like a rock and swinging by over 1.0, daily, with little or no change in the solution strength. There are more details here:

https://www.icmag.com/ic/showthread.php?t=211503

This is one of those things that seems to continually crop up in DWC related threads. Root zone issues or silica supplementation are 2 of the more common possible causes mentioned; both of which are related to nutrient solution composition. It's a dance, started many times, that I have yet to see brought to a satisfactory conclusion. Happens regardless of whether tap water or RO water is used; and, and with or without the use pH buffered base nutes.

While many growers successfully bring in grows with fluctuating pH; it is far from a given. The fact that it really does not seem to manifest until well into flower just causes more stress, as there is more to lose.

What do the tree mavens have to say about this topic, given that most such grows are done in DWC variants? Are these swings just part of DWC grows, that can be dealt with by large infusions of pH UP; or, is this just a band-aid solution, as likely to add to the problem as it is to remedy it? If such swings are caused by the starchs and sugars in bloom boosters and sweeteners, are there similar, non-organic supplements that can co-exist with H2O2? Do these additives reliably increase yield enough to justify using them in DWC?

That's oversimplistic and will only work if the solution strength increases while pH drops. Even then, it's questionable whether the addition of water alone will cover the drop, as nutes are not depleted at the same rate. The further from change-out the greater the ratio shift.

Ranta, take a look at my thread and you'll see I'm getting daily swings of 1.0 or greater; adding water alone will raise pH from 4.7 to 4.9, maybe even 5.0, for all of the 3 minutes or so that it takes for the pump to send the res contents into the buckets. While water alone may work for small fluctuations, more is required in some set-ups; as BudMasterzero points out, this is a recurring comment in DWC systems.

Possible causes can be as simple as sizing a res too small for the plants, and range through water issues to strains that feed disproportionally heavy on 1 nute or family of nutes. The source of nutes, such as potassium silicate, is also stated as a contributing factor. Then there are rootzone issues such as the chemical interaction of roots and nutes; or, root rot.

These are some of the key points in the discussions regarding stand-alone DWC v RDWC; or running beneficials v sterile solutions. Given that most of the growers who routinely grow trees seem to run variants of DWC, those of us who want or need to get as much weight as possible, from a limited number of plants, look at this as a viable option. Learning how to do so, without accepting the inevitability of losing a crop, is the trick. It's only by gaining knowledge of all the variables involved, that we increase our yields and success rates.

I feel like stagetek would sympathize with the issue I'm having now.

The problem with this "rule of thumb"...:
"Rough rule of thumb is:

• pH drop with nute strength increase; back off on nutes
• pH rise with nute strength decrease; plants want more nutes
• solution in res drops with pH and nute strength stable; it's a good thing"

...is that it omits the rest of the scenarios. What about pH drop with Nute drop? What about pH rise with Nute rise? and only one scenario even refers to what going on with the water level.
What about large pH drop with Nute stable and large drop in solution?
I have tried to do "less is more" with nutrient to be safe and it hasn't helped very much. I had a situation most would say is too high ec (and it was only about 450 to 550ppm) that I tried to resolve with dropping the ec slightly and that did me no good.
Plant is now drinking between 1 and 2 gallons per day(!) - which is great - but the pH is dropping and the nute ppm is staying the same-ish. The roots seem good, though for day 38 I think the buds could be a little bigger.

Please check out this intersting thread from thctalk; the member "Woody J" has some interesting posts. I think the only thing I haven't tried is the thing that seems counter intuitive; that is to raise the ppm in my scenario. It seems retarded. Since I think the plant seemed to get minor leaf tip burn at around 500 with my "less is more" approach. Just to see what happens... but I dont want to risk harvest or burn roots.
LINK