Do you adjust pH when watering?

[Ray]

Steven,

No doubt "goodgolly" will jump on this, but in very simple terms, "buffering" is a phenomenon in solutions in which a sufficient amount of ionization has occurred, so that when more ionizable ingredients are added, the pH does not change drastically. Think of it as "pH stabilization".

"Pure" water, having no dissolved ionizable species (or even if there's some carbon dioxide in it), is unbuffered, so if you add a typical, off-the-shelf fertilizer to it, the resultant pH will likely be VERY acidic, to the point where the result can be damaging - which might be a combination of direct tissue damage and/or toxicity, due to the different solubilities of different minerals at varying pH's. That's why "RO Fertilizers" were developed, as they have been formulated with minerals that will give us the pH we're looking for, without need for adjustment. Most well- or tap water, on the other hand, has plenty of dissolved minerals, so is buffered, and adding more minerals via fertilizers does not affect the pH as drastically.

The concern I have with watering with pure water relates to mineral residues in the pot: we really don't know what they are (chemically), so we don't know what the resultant pH is likely to be. It might not even be worth worrying about...

[goodgollymissmolly]

I don't disagree at all. However, I do use MSU pure water formula. I do flush thoroughly so that any in-pot issues are at least flooded to minimize any effect.

I will collect data on pot effluent as soon as my new pH meter arrives. The problem I have with "city" water here is that our whole state is limestone..much of it on the surface. Our water comes from a river that has cut a 300 foot deep ditch through limestone. In fact, the 4th highest interstate bridge in the country is 2 miles from my house. It's not high because it's on a mountain. It's high because the river dug a heck of a ditch.

In short the TDS of my city water is over 300 ppm and the pH is 7.3 (measured while I had a good pH meter). So you can see why I have no interest in watering with city water. My greenhouse is pretty big so I have plenty of roof to collect rainwater from and I've set up a good system.

That's my story and I'm sticking to it.

[Ray]

I know what you mean about the water. My first job out of school was with Corning (refractories development) in Louisville.

The water was so hard, you could see stalagmites growing in the pots!

[Des]

Wow, this has been an interesting discussion and I must admit some of it beyond my understanding.I grow my cymbids to a program which I developed and refined over a number of years ,ph is the first item on the program, my plants and some success on the show bench tell me that I must be doing something right

[IdahoOrchid]

Originally Posted by rsfrid

I'd like to know as well. I just ordered this one CHECKER1 pH Meter - CHECKER1 which seemed cheap enough and seems to have pretty good specs, but I'm a real duffer on this stuff.

Would one of the more experienced water people give their comments on this meter. Is it sufficiently accurate for hobby needs?

[goodgollymissmolly]

Steven, I know nothing about this product. I can tell you that Hanna is a legitimate name in the pH meter field. The stated 0.2 pH accuracy is probably an oversimplified statement, but extreme accuracy is not necessary for what we are trying to accomplish.

It is not clear to me that the $29 quoted price includes the electrode. If you have to buy the electrode separately, then it's another $19. If the price does not include the electrode then I would question the reliability and truthfulness of the vendor because you have no meter without an electrode. It's probably OK, I'm just a suspicious person by nature.

I just bought another Milwaukee SM100 like my old one. They are $85 to 105 at various internet vendors. I don't recommend this one or any other one. It's just the one I had for a long time.

I'd say the one you are looking at is just fine.

[Ray]

I have the pH Tester 2 WD-35624-22 pH Tester - WD-35624-

When calibrated as GoodGolly mentioned previously, it's quite good.

[Ross]

Originally Posted by goodgollymissmolly

It is not clear to me that the $29 quoted price includes the electrode.

I also ordered the "replacement" electrode just in case. I also am doubtful by nature and just like to be sure.

[goodgollymissmolly]

Received my new Milwaukee SM-100 pH meter today. I calibrated it at 7 and 4 with brand new calibration solution.

Here are the results I obtained on the things we discussed earlier:

Rainwater collected mostly last week off the polycarbonate roof of my greenhouse and stored in a new 225 gal polyethylene tank inside the greenhouse was ...........5.8 pH

Same water with 1/4 teaspoon MSU pure water fertilizer per gallon was..............5.3 pH

Same with 1 teaspoon per gallon MSU pure water fertilizer............4.9 pH

My tap water..........7.3 pH

I also put the new probe on my old meter and it woked fine so it was my probe that failed. Get a new one and I have two meters...wooopeeee.

Guess I need to add some tap water to my rainwater. I believe I can add about 20% tap water and keep the TDS under 100ppm. That should get the pH around 5.5 with the 1 teaspoon dose of fertilizer.

Jim

[Ross]

Originally Posted by goodgollymissmolly

Guess I need to add some tap water to my rainwater. I believe I can add about 20% tap water and keep the TDS under 100ppm. That should get the pH around 5.5 with the 1 teaspoon dose of fertilizer.

Jim

Jim, couldn't you just add pH increaser like Jungle products makes for aquariums?