# Water pH



## papheteer (Jan 26, 2016)

To those that adjust their water and fertilizer solution pH, what do you aim for? Also what type of chemical do you use? Thanks!


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## cnycharles (Jan 26, 2016)

I would think aiming for 5.5 to 6.5 depending on what conditions the plants prefer, and depends on if you need to raise or lower the pH. Citric acid could be used to lower and baking soda or potassium bicarbonate could be used to raise


Elmer Nj


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## consettbay2003 (Jan 30, 2016)

I recall Rick mentioning that a ph of 5.8 was ideal for nitrate absorption.


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## Ray (Jan 30, 2016)

The pH of the applied solution is not the only factor in what determines the pH. The potting medium, the plant, and micro flora and -fauna all affect the rhizosphere pH.

Many moons ago, a few folks experimenting with semi-hydroponics for the first time measured the pH of the reservoir. Starting with a solution pH of 6, depending upon the time of day, and time since the plant was watered, we saw readings as low as 3.4, especially early in the morning. Some were higher than 7, but I don't recall exactly.

In that case, the medium played no role, as the LECA was inert, so I attributed it to the plant itself.

I think the best way to see what's really happening is to saturate the medium with your regular solution, wait an hour or two, then barely dribble more solution through the pot. Collect the drainage and measure that.

After seeing the swings in pH in S/H pots, I have decided to take a much simpler approach. I just don't worry about it.


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## Linus_Cello (Jan 30, 2016)

Ray said:


> The pH of the applied solution is not the only factor in what determines the pH. The potting medium, the plant, and micro flora and -fauna all affect the rhizosphere pH.
> 
> Many moons ago, a few folks experimenting with semi-hydroponics for the first time measured the pH of the reservoir. Starting with a solution pH of 6, depending upon the time of day, and time since the plant was watered, we saw readings as low as 3.4, especially early in the morning. Some were higher than 7, but I don't recall exactly.
> 
> ...



Has anyone tried adding to LECA in s/h chips of dolomite or oyster shell to try to buffer plants that come from karst/limestone regions? I'm not aware of PK growing s/h successfully; maybe it could be it needs a buffered higher pH?


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## Rick (Jan 30, 2016)

consettbay2003 said:


> I recall Rick mentioning that a ph of 5.8 was ideal for nitrate absorption.



Kind of Consettbay, but also inform with what Ray is adding.

The pH of the rhizosphere for optimum nitrate absorption is around 5.8 s.u. But the plant wants to regulate that pH itself through organic acid exudates rather than what the pH of the water passing by the roots is (it goes by too fast to make a difference).

So for momentary water applications (not continuous like in SH) a pH of 5.8 is a good match for what the plant is trying to do itself, and I would use citric acid (or a mix of citric and malic acid) since that is what the plant is generally using in its exudates.

As Ray noted sometimes the pH goes up. This is supposed to happen as a plant picks up nitrate - converts it to ammonia - discharges OH- it raises the pH of the rhyzosphere. And if the potting system contains a bunch of pH buffering materials the system will fight with what the plant wants to do to pick up nutrients.

But if you have ammonia in the nutrient pot the complete reverse happens.

And none of this accounts for what the bacteria in the pot are doing.

So as Ray said the complexity can make you crazy. 

The pH 5.8 target I use is a "do not go below" target for my citric acid addition. So it lets me know that I've added enough acid, but I don't do it because I'm worried about optimizing the pH of the irrigation water for watering sake.


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## Rick (Jan 30, 2016)

cnycharles said:


> I would think aiming for 5.5 to 6.5 depending on what conditions the plants prefer, and depends on if you need to raise or lower the pH. Citric acid could be used to lower and baking soda or potassium bicarbonate could be used to raise
> 
> 
> Elmer Nj



If the pH is strongly acidic (less than 5.0s.u.) I would suggest reducing the fertilizer concentration first.

And I would use lime or magox before adding using potassium salts.


You could dissolve some pelletized dolomitic lime in water and make a nice pH up adjust solution that will be Ca and Mg based instead of Na or K based.


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## Rick (Jan 30, 2016)

Linus_Cello said:


> Has anyone tried adding to LECA in s/h chips of dolomite or oyster shell to try to buffer plants that come from karst/limestone regions? I'm not aware of PK growing s/h successfully; maybe it could be it needs a buffered higher pH?




PK do great SH or ebb/flow. They use tons of water.

Just to illustrate what Ray was talking about, I measured the tank pH of my two PK that are in SH-ish systems (baskets of moss and heavy limestone chips sitting in a shallow tray of water). With the exception of the age/size of the plants the systems are as close to identical and sit next to each other.

The tank pH of the big plant with lots of live moss growth was ~6.5. The smaller plant with not much live moss growth was ~5.0 (so I changed out the water with my well water:wink

Now both of those systems get a enough fresh water daily with a light dose of fert (N = 2-5ppm) pH adjusted to about 5.8 with lemon juice to keep the tank level stable.

So what does the pH of the irrigation water have to do with the tank pH
Also these baskets are full of coarse limestone so are they making a difference on pH?


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## Justin (Jan 30, 2016)

i try to aim for 6.5 usually. but i haven't checked/adjusted pH in over a year. 30-10-10 added to tapwater brings it right in line for me so i just go with it.

i am in the middle of switching to orchiata though so i need to do some tests with the runoff vs fir bark.


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## Rick (Jan 30, 2016)

Justin said:


> i try to aim for 6.5 usually. but i haven't checked/adjusted pH in over a year. 30-10-10 added to tapwater brings it right in line for me so i just go with it.
> 
> i am in the middle of switching to orchiata though so i need to do some tests with the runoff vs fir bark.



Excellent plan Justin

As Ray suggested its almost more important to see whats coming out of the bottom of the pot to figure out what to do going into the pot.

In some ways that is similar to the practice of looking at leaf tissue values. 

Looking at end results helps inform the front end practice:wink:


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## Ray (Jan 31, 2016)

Justin, FWIW, I use Orchiata, LECA, EcoWeb, & sphagnum depending upon the plant. They all get the same feeding and watering regimen, and I can see no differences in their growth.


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## gonewild (Jan 31, 2016)

Ray said:


> In that case, the medium played no role, as the LECA was inert, so I attributed it to the plant itself.



Ray FYI.... the LECA was not inert, it did influence the pH. The brand and structure of LECA made a difference as we saw when your PrimeAgra changed color and shape.

There are some LECA companies that state their pellets are pH9.5.


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## gonewild (Jan 31, 2016)

Linus_Cello said:


> Has anyone tried adding to LECA in s/h chips of dolomite or oyster shell to try to buffer plants that come from karst/limestone regions? I'm not aware of PK growing s/h successfully; maybe it could be it needs a buffered higher pH?



You can do a forum search back in time, I posted a lot about growing PK in LECA. I did extensive tests with adding limestone to the LECA. For PK it improved growth. PK will grow using the s/h method but it grows tremendously better if you water overhead....In LECA water everyday works great. PK absolutely likes to be wet.


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## Ray (Feb 1, 2016)

gonewild said:


> PK will grow using the s/h method but it grows tremendously better if you water overhead...



If you are doing semi-hydro culture properly, you DO water from overhead.


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## gonewild (Feb 1, 2016)

Ray said:


> If you are doing semi-hydro culture properly, you DO water from overhead.



I know.
What I was saying is that PK grows OK using the proper S/H method.

BUT

If instead of relying on the S/H wicking method for watering you water the same pots of LECA in the same side drain reservoir pots overhead the PK grow much better. 
Overhead watering was better than s/h. 
Using the side drain pots with LECA allows for daily watering and the PK grow better. Having the reservoir style pot and LECA serves as a backup for the times you can't water daily. 
Perhaps every few days is enough in your environment for PK but I found excellent results watering everyday with nutrients and as well the pants received intermittent mist all day long every day.


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## trdyl (Feb 1, 2016)

Linus_Cello said:


> Has anyone tried adding to LECA in s/h chips of dolomite or oyster shell to try to buffer plants that come from karst/limestone regions? I'm not aware of PK growing s/h successfully; maybe it could be it needs a buffered higher pH?



I started growing a PK seedling in s/h buffered with oyster shell in July of 2014. When I was setting it up I was shooting for a flooded pH of 8.0 measured a couple of hours after flooding. At the time it looked to be a few months out of flask. Now one growth later it is in spike. It is still a small plant with a leaf span of 11 inches. But it seems to be happy enough.


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## Linus_Cello (Feb 1, 2016)

trdyl said:


> I started growing a PK seedling in s/h buffered with oyster shell in July of 2014. When I was setting it up I was shooting for a flooded pH of 8.0 measured a couple of hours after flooding. At the time it looked to be a few months out of flask. Now one growth later it is in spike. It is still a small plant with a leaf span of 11 inches. But it seems to be happy enough.



Hope you can post pics of this (in flower)


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## trdyl (Feb 1, 2016)

I will certainly try. I've heard that these (PK seedlings) blast their spikes at a young age. Only time will tell with mine.


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## Ray (Feb 2, 2016)

Sounds like you and I are describing different parts of the elephant....

Semi-hydroponics, by definition, requires a reservoir. 

In "Leni", or "Luwassa" pots, with the inner culture pot and outer reservoir pot (usually with a gauge to tell you the reservoir depth), the effort required to lift the plant and culture pot out of the reservoir, dump it, then reassemble and water is a deterrent to doing it often.

In my side-drainage pots (or standard, bottom-draining pots standing in a tray), there is still a reservoir below the drainage holes, but there is no limit to the frequency with which one can water, and when you do so, you flush/saturate/and refresh the chemistry of the liquid remaining in the pot, which, in my opinion, is important to prevent the plant from "sitting in its own poop", and slowing its growth.


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## gonewild (Feb 2, 2016)

Ray, I guess I'm assuming when most people think "s/h" culture they think water reservoir in the bottom of the pot and then relying on the wicking of the reservoir water to water the plant. 
For PK the wicking was enough to keep the plant alive and growing at a moderate slow rate. By watering overhead frequently and not relying on or utilizing the wicking of water the PK grow much faster. For PK having the reservoir at the bottom is important because they like to be extra wet and the reservoir replicates placing a standard pot standing in water like many growers have adapted to.
With PK the pot reservoir offers an advantage to growing in a tray of water because it helps keep the roots contained in the pot rather than growing out freely into a tray of water. (PK does not like having it's roots broken at repotting time.)


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## Ray (Feb 3, 2016)

Semi-hydroponics has the advantage of maintaining a very stable root zone environment, compared to more traditional culture. Watering daily has absolutely nothing but a positive effect on the plants. Conversely, it can also play a role as a "watering frequency buffer" if you can't water frequently.

I had a paph hybrid in a 6.5" pot that bloomed-out in my kitchen, then I took it to my basement (dry, cool, dark) to divide and repot it. I let it go for a while, then had to go to Canada to help a family member getting out of the hospital, then came back and caught up on orders, so all-in-all, that plant sat unattended for six weeks. The slow release of the moisture from the LECA kept it just fine for the duration. Once placed back in the greenhouse, it jumped right back into active growth. 

I certainly don't recommend that kind of mistreatment, but it protected the plant from my inaction.

Unlike fertilizer in that other thread, when it comes to watering, "more is better than more".


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## Linus_Cello (Feb 3, 2016)

Ray said:


> Conversely, it can also play a role as a "watering frequency buffer" if you can't water frequently.



Conversely, it's an idiot proof method to prevent root rot. I've had neighbors take care of some of my orchids for vacation, and I tell them NOT to have the pot sitting in water... can't do that with the side holes in s/h.


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## Justin (Feb 13, 2016)

Finally got out the pH indicator...

Water out of tap = 8.5
Irrigation solution 1/16 tsp (or a smidge more)/ gallon 30-10-10 = 7.0
Runoff from 4" pot w/1 year old fir bark mix = 6.5
Runoff from 4" pot w/ 1 month old orchiata mix = 7.0


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## Stone (Feb 14, 2016)

Ray, What's the story with LECA accumulating salts? Does it (LECA) have any sort of CEC? (if not, I presume that it can be flushed at any time to lower salt content). I was told by one grower here that there was a problem of salt build up but he was using it only as an ingredient in traditional potting not permanently wet as in SH etc. Have you monitored EC of the well water over time and is flushing/watering with nutrient better for maintenance as apposed to just topping up the well with plain water with periodic feeding?


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## Ray (Feb 14, 2016)

Mike, 

Most brands of LECA have extremely low CECs. In inorganic materials, it tends to be the edges of clay particles that play the biggest role in that respect, and in a fired clay body, those edges have mostly been thermally modified or even vitrified.

Mineral buildup, therefore, is merely the "sponge effect", less than a case of being bonded to the substrate. Consider this scenario:

Pellet saturated with a liquid containing dissolved solids. Every pore contains the same solution. As the water at the surface begins to evaporate, those dissolved solids migrate toward the center of the pellet, as physics tries to eliminate the concentration gradient. Eventually, when enough of the solvent has evaporated, and a solubility limit has been reached, precipitation occurs.

Rewetting it may redissolve some of that precipitate, but not all of it, so by repeating those resaturate/redry cycles leads to visible buildup.

I will add that in the situation of LECA in S/H culture, if done in a high-humidity environment that does not favor evaporation, that buildup rate is VERY low, so you can get away with long periods between necessary repotting. If one often sees the tops of the medium dry out, then more frequent repotting is required - it may only need the top inch or so replaced, but it is something to consider.


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