What is PH?

[Racefan]

What is pH?
pH is one of the most common analyses in soil and water testing. An indication of the sample’s acidity, pH is actually a measurement of the activity of hydrogen ions in the sample.
pH measurements run on a scale from 0-14, with 7.0 considered neutral. Those solutions with a pH below 7.0 are considered acids, and those above 7.0 are designated bases. The pH scale is logarithmic, so a one unit change in pH actually reflects a ten-fold change in the acidity. For instance, orange juice (pH 4) is ten times more acidic than cottage cheese, which has a pH of 5.
Many industries rely heavily on pH for their processes to work properly, or to maintain expensive equipment. Breweries maintain the pH between 4.2 and 4.6 to keep infectious bacteria from breeding during the fermentation process. In many industrial applications, if the pH is too low the water may corrode metal equipment, but if it is too high scaling may result.
pH can be measured visually or electronically. Visual comparisons use a pH indicator whose color change reflects the pH, which is then matched to a color
standard. pH meters, such as the pH 5, simplify the pH test. A probe is placed in
the sample, and the pH is read directly from the meter.
While the meter is very easy to use, the electronics within the meter are more
complex. After the pH probe measures the millivolts of potential between the
reference electrode and the pH electrode, the meter converts this reading to pH
units using the Nernst Equation:


where Ex = constant depending upon reference electrode
R= constant
Tk = absolute temperature
n = charge of the ion (including sign)
F = constant
ai = activity of the ion

Electrode Cleaning
Because your pH electrode is susceptible to dirt and contamination, clean it
every one to three months depending on extent and condition of use.
Clean the electrode in a mild detergent solution. Wipe the probe with a soft
tissue paper. Avoid touching the glass membrane with your fingers. Rinse
thoroughly in tap water and then in distilled water. Recalibrate your meter after
cleaning the electrode.

Storage
The pH electrode should always be stored in the soaker bottle. The cap should
be tightened to prevent leaks. The soaker bottle contains a dilute solution of
potassium chloride.

Special Cleaning Tips
Salt deposit: dissolve the deposit by immersing the electrode in tap water for ten
to fifteen minutes. Then thoroughly rinse with distilled water.
Oil/grease film: wash electrode pH bulb gently in detergent solution. Rinse
electrode tip with distilled water.
Clogged reference junction: heat a diluted KC1 solution to 60-80°C. Place the
sensing part of the electrode into the heated solution for about 10 minutes.
Allow the electrode to cool in some unheated KC1 solution.
Protein deposits: prepare a 1% pepsin solution in 0.1M of HC1. Place the
electrode in the solution for five to ten minutes. Rinse the electrode with
distilled water.

[McBudz]

It can be very difficult near impossible to grow a healthy plant without proper understanding of pH and the tools to monitor and adjust the pH.

A must is a good digital pH meter.

I feel like this should be a sticky. A lot of beginner growers including myself treated pH as an after thought. These days I spend close to an hour carefully testing and adjusting my pH each feeding/watering and my results have improved drastically.

IMO pH issues are the root of almost every mystery problem.

Great thread.

[Frog]

A blast from the Past

Will my nitrogen source affect the PH?
Contributed by: diels alder

The source of nitrogen in your fertilizer affects the pH of the medium you are growing in. The standard of measure of how acidic/basic a source is, is calcium carbonate, a common water mineral. Calcium carbonate is the major contributor of water alkalinity, the capacity for water to 'soak up', or buffer, acidity in water and lead to a high pH.

Note that it is much easier to lower the pH of water through the acidity of a given nitrogen source than it is to raise it, as nitrates are less basic than ammonium is acidic.

code:--------------------------------------------------------------------------------
N Source Potential acidity Potential Basicity
Ammonium sulfate 2,200 0
Urea 1,680 0
Diammonium phosphate 1,400 0
Ammonium nitrate 1,220 0
Monoammonium phosphate 1,120 0
Calcium nitrate 0 400
Potassium nitrate 0 520
Sodium nitrate 0 580
--------------------------------------------------------------------------------
Potential acidity = # of lbs of calcium carbonate needed to neutralize acidity of one ton of source.

Potential basicity = one ton of source has same effect as this many lbs of calcium carbonate.

Source:GrowFAQ © 2000-2004 Overgrow

[McBudz]

I was going to put this in a problem thread but feel as though it will get better visibility here. So I'll keep here...

pH is extremely important and one of the most often overlooked parameters by new growers. I know because I also overlooked and underestimated the importance of pH when I started growing.

In soil the pH must be between 6.3 and 6.7. Period well + or - .1 some will argue. This is a very finite range. You will find out it does not take much to skew pH too much in either direction. many soil growers battle to keep pH up at acceptable levels while many hydro growers fight to keep the pH down to acceptable levels.

Why pH tends to go low in soil...

Most soil / soilless mediums are comprised of some failry large percentage of sphagnum moss. As this moss degrades and breaks down it becomes very acidic thus effecting nutrient uptake by way of lockout. Certain nutrients/elements get locked out at either too low or too high of a pH. This is noticable by plant show extreme deficiencies of one or more nutrients when you are feeding the plant all nutrients and the leaves may also look crumpled or twisted.

Best way to counter this in soil is to "sweeten" the soil by adding pulverized dolomitic lime which is very alkaline. A little bit goes a long way. It will help keep the pH stable offsetting the acidic breakdown of the moss.

Why pH tends to go HIGH in hydro...

Water with nothing in it is pH neutral. or pH of 7.0

Adding your hydroponic nutrients to the water will tend to bring the pH down. The nutrients them selves have acidic properties. Either naturally or are made this way by the nutrient manufacturer to help get your reservoir to an acceptable pH range. In hydro it tend to be a negative pH shift of about .7 of soil acceptable range. so 5.5 -6.2 or so. In hydro it is beneficial to flux within the range to best absorb all nutrients. So set res at 5.5 let flux to 6.2 then bring back to 5.5 etc.

As the plant absorb the nutrients (remember which are acidic and lowering the pH) from the water the pH will shift north towards neutral.

The more plants you have and the less reservoir space you have will lead to huge fluctuations in a short period of time. Unless you want to stand over your reservoir constantly monitoring and adjusting for pH and PPM then you should plan on 5 gallons or more of reservoir volume per plant.

[fakirr]

Is there any cheap/household items i can use to lower my PH level from 7.0 to 6.5?

[skinneh]

vinigar & lemon juice are just quick ones of the top of my head.

[Joe Coffee]

I bought a Moser Lee Soil Master Moisture Light & PH meter what a piece of shit... It's goin back to Lowes.

[siscokid]

Question, if my soil ph is 7 should i adjust my plant food to be 6.4 or lower? I mixed an all purpose plant food from vigoro with tap water and tested it and it is at 6.4

[Joe Coffee]

Just picked up the Ferry & Morse Electronic Soil Tester in the Garden Department at Home Depot for 18.99. This seems to work real well. The instruction guide is a good read.. Take the time and read it...

[HAPPY GRASS]

I am growing in 3 gallon grow bags about to go into 5 gal pots with 50/50 Happy Frog and Fox Farms Ocean Forest soil. How can I measure my soil's PH? If my soil PH is low, what is a household item can I use to bring my PH up? How often should I use it? Approximately how much do I use per gallon of soil? & in what way do I apply it?

[ultrasonic]

Just because I thought It was interesting, and I'm surprised more people don't ask, PH stands for Potential of Hydrogen.

Feed on THAT knowledge. Great sticky BTW, learned me some, thanks!

[greenblood]

Invaluable information for beginners like me!