pH On the Fritz!

One thing I hear a lot about, it what is causing pH fluctuation. There are several
pieces of information which the majority of self taught growers are unable to gain
access to. This is because much of the information the mainstream is able to
obtain is reliant upon manufacturers of nutrients, and medium.

One of the biggest misconceptions in hydroponics growing is that the pH in your
nutrient reservoir is the single biggest thing having to do with pH that affects the
outcome of your crops. It's simply not true. There are 3 things which you have
to take in to account in order to determine your pH.

1. Water.

2. Growing Medium.

3. Nutrient Analysis.

Obviously, these things all need to be taken in to account, but how do we do that?

First things first, pH, stands for potential hydrogen. It is a measurement of possible
hydrogen and hydroxide ions. The pH scale is from 0-14, 0 being acidic, and 14
being alkaline. When your water, growing medium or nutrient solution is acidic
(below a pH of 7.0) it contains more hydrogen ions than hydroxide ions. And
when your water, growing medium or nutrient solution is alkaline, also referred
to as base or basic (above a pH of 7.0) it contains more hydroxide ions than
hydrogen ions. These hydrogen and hydroxide ions interact with each other and
perform a balancing act of sorts that determines the pH in your water, growing
medium and nutrients.

These hydrogen and hydroxide ions are also in the elements that make up our
macro and micro nutrients of the nutrient solutions we use to grow our plants
with. And because of this the elements that make up our macro and micro
nutrients are classified into two distinct groups. One group of elements are called
cations and contains more hydrogen ions. The other group of elements are called
anions and contain more hydroxide ions. Also our growing medium pH is
dramatically affected by these cations and anions contained in the macro, micro
and secondary nutrient elements we use. Remember this because it’s important.

The macro, micro and secondary elements that are cations are urea and
ammonium (both are forms of nitrogen), potassium, calcium, magnesium, iron
zinc, manganese copper and cobalt. And the elements that are anions are
nitrates (another form of nitrogen), phosphates (phosphorus) sulfates,
carbonates and bicarbonates. This list covers the most common cations and
anions.

Contrary to popular belief a pH of 7.0 is not always neutral, in fact it really depends
on the temperature of your nutrient solution as the chart above shows. That’s why
it’s critical to make sure you buy a pH meter that compensates for temperature.

a pH of 7 is considered to be pH neutral, but in fact is only an approximation and is
accurate only at 25 °C or 77°F. A true neutral pH is when the concentration of
hydrogen ions (H+) is exactly the same as the concentration of hydroxide ions
(OH- ) and those concentrations are effected by temperature so your pH neutral
point varies from pH 7.47 at 0°C or 32°F to pH 6.14 at 100°C or 212°F.

More to come.

You would think that your biggest concern would be about the pH in your reservoir.
Actually You should be more concerned with your water’s alkalinity. This is one of
the major culprits that will affect your yields. In fact, one of the biggest problems
with water is its alkalinity.

Your water is not just water. There is a lot of other stuff in it. The alkalinity of
water is the concentration of all sorts of ions in it, like calcium, magnesium,
sodium, potassium, both come in the forms of carbonates and bicarbonates. And
bicarbonates are the worst offenders of the two.

depending on what crop is being grown, the fertilizer being injected will be
balanced with the correct cation to anion ratios for that crop’s soil pH
requirement. If they need to lower their soil’s pH they’ll use a fertilizer that has
more cations than anions. And if they need to raise the soil’s pH they will use
fertilizer with more anions than cations.

Difference between Water Hardness and Alkalinity is “Hardness” is the measure
of the combined concentration of insoluble calcium and magnesium in the
water, not the presence of the carbonates or bicarbonates mentioned earlier.

Using a water softener to handle the hardness will only displace the calcium
and magnesium ions and leave the carbonates and bicarbonates behind, which
doesn’t change the alkalinity at all. So this is not the thing to do. And a BIG
WARNING, using a water softener will add unwanted sodium to your water
severely decreasing your yields. If you’re using well water it is almost
guaranteed you will have alkalinity problems. In fact most municipalities have
water that is poor quality and has alkalinity. Suggestion? Reverse Osmosis.

Now how about this for some variation? Taking pH readings during the light
cycle will give you a different result than when you take pH readings at night.
The reason for this is, during the dark periods, both microbes and the plants are
resting and give off alkaline molecules and the pH tends to go up a bit. During
the day the plant and microbes are active and they give off acid molecules which
make the pH go down some. If you’re running a recirculation system this is
important to consider, especially because your tank should be outside your grow
room. And you might be taking your readings when your plants are in their dark
cycle.

Shrubs First said:

You would think that your biggest concern would be about the pH in your reservoir.
Actually You should be more concerned with your water’s alkalinity. This is one of
the major culprits that will affect your yields. In fact, one of the biggest problems
with water is its alkalinity.

Your water is not just water. There is a lot of other stuff in it. The alkalinity of
water is the concentration of all sorts of ions in it, like calcium, magnesium,
sodium, potassium, both come in the forms of carbonates and bicarbonates. And
bicarbonates are the worst offenders of the two.

depending on what crop is being grown, the fertilizer being injected will be
balanced with the correct cation to anion ratios for that crop’s soil pH
requirement. If they need to lower their soil’s pH they’ll use a fertilizer that has
more cations than anions. And if they need to raise the soil’s pH they will use
fertilizer with more anions than cations.

Difference between Water Hardness and Alkalinity is “Hardness” is the measure
of the combined concentration of insoluble calcium and magnesium in the
water, not the presence of the carbonates or bicarbonates mentioned earlier.

Using a water softener to handle the hardness will only displace the calcium
and magnesium ions and leave the carbonates and bicarbonates behind, which
doesn’t change the alkalinity at all. So this is not the thing to do. And a BIG
WARNING, using a water softener will add unwanted sodium to your water
severely decreasing your yields. If you’re using well water it is almost
guaranteed you will have alkalinity problems. In fact most municipalities have
water that is poor quality and has alkalinity. Suggestion? Reverse Osmosis.

Now how about this for some variation? Taking pH readings during the light
cycle will give you a different result than when you take pH readings at night.
The reason for this is, during the dark periods, both microbes and the plants are
resting and give off alkaline molecules and the pH tends to go up a bit. During
the day the plant and microbes are active and they give off acid molecules which
make the pH go down some. If you’re running a recirculation system this is
important to consider, especially because your tank should be outside your grow
room. And you might be taking your readings when your plants are in their dark
cycle.

Click to expand...

great read--thanks for putting that up here...funny thing I was no 5 minutes ago just stumbling onto this alkalinity via muni/city water--- R.O is the way to go as a matter of fact that is what I just switched to about 3 days ago. Great post +rep

On to the growing medium – A lot has been said about measuring pH in the
nutrient solution, but where the real money is being won or lost by the buckets
full, is in the actual growing medium itself and here's why. Your plants’ root
system is actually a pH excreting machine that manufactures and pumps hydrogen
ions (pH down) or hydroxide ions (pH up) directly into your growing medium and
will directly change the pH of the growing medium depending on the elemental
composition of your nutrients make up.

All in all it’s your growing medium that you need to be most concerned about.
Because if you want a really great crop, your plants must have an acidic pH
growing medium. In most cases your pH will be climbing and your challenge will be
to keep your pH from going up.

Sure, the water, the growing medium, and the nutrients should all have to work
in perfect harmony with each other, but it’s the roots in the growing medium
that drives the pH chemical reactions that is the most overlooked by growers
and it’s not anyones fault it’s just most books out there don’t go into great depth about it.
And naturally this is very important because, the pH in the root zone is going to
determine the availability of nutrients and your plants ability to produce world
class buds.

Iit’s going to be essential then if you want big consistent yields, you should check your growing medium pH every week.

There have been extensive tests on hydroponics nutrients, and unfortunately
the vast majority of them don’t work with the plants root system to even
remotely come close to maintaining a stable or ideal pH in the growing medium.
Because they use too much nitrates as there source of nitrogen. Here’s the
straight goods... and an education for a lot of the nutrient manufacturers
out there, to balance a growing mediums pH, nutrient manufacturers must be
using the correct balance of cations to anions to guarantee you the right pH in
your growing medium. And...One more thing, the right balance of elements
(cations to anions) that will give you a stable and ideal growing medium pH is
different from plant species to plant species. And by not being aware and acting
on this vitally critical piece of knowledge is exactly like growing with one foot on
the gas and the other foot on the brake at the same time.

I go on the forums all the time, and it always amazes me when I see people
making statements like, “all base nutrients are the same and salts are just
salts”. Think about it... is there a difference in the foods you eat. Are your
sources and quality of proteins, carbohydrates and fats you eat, all the same?
Absolutely not, some proteins are assimilated and utilized by your body faster
and more completely than others. And some carbohydrates release quickly and
spike your insulin while others are a slow burn and give you sustained energy.
What about fats? Some are actually good for you like Omega-3 and others will
slowly clog your arteries and eventually give you a heart attack. Obviously it all
makes a difference.

There is a variety of growing mediums to choose from. You have sphagnum moss
– that stuff from bogs. And there is coco coir, the fiber that comes from the
coconut’s outer husk. And let’s not forget about the special mixes and all the other
hydroponic growing mediums. Now you might want to keep it simple so what
I recommend is that you use Sunshine #4 mix. This is a mix that is pretty close to
ideal and will save you a lot of work. We’ll talk a bit more about that later.
You might even choose coco coir since it is also a good growing medium and has a
special line of compatible fertilizers. The thing about different hydroponic mediums
is that they have varied abilities to maintain and control pH.

Those are some basic growing mediums. In hydroponics, there are two basic
types of growing mediums: those that are pH independent and those that are
pH dependent. Let’s take a closer look at these mediums differences. Well, each
one of them has a certain ability to stabilize or buffer pH, which is another way
of saying they have varied abilities to keep the pH from changing on you. This
ability is called cation exchange capacity or CEC. In other words, CEC refers to
the ability of the medium to absorb and release cations. Remember the cation
stuff I mentioned earlier? Here are a few mediums.

Rock Wool low CEC
Coco Coir Medium High CEC
Pete Bog Sphagnum Moss Harvest High CEC
Sphagnum Moss very high CEC
Sunshine #4 Mix High CEC
Perlite Expanded Clay Pellets low CEC

Mediums that are pH dependent have little to no CEC and cannot resist a
change in pH and this results in the pH going high or low very rapidly.
So, then, mediums that are pH independent have a high CEC, are more buffered
and can resist a change in pH for long periods of time. And that’s good! That’s
what you want. As an example your everyday, garden, soil-based medium
contains some humus and clay and is pH independent with a high CEC because
of the humus and clay. They are great to grow plants in because it is not affected
by rapid pH swings.

Monitoring growing medium pH is One of the most overlooked areas by growers
is checking their growing medium pH on a regular basis. That is probably the
biggest single culprit for yield inconsistencies from crop to crop and it could be
costing you a lot of money. Let me explain how this happens. As the roots take
in an element, it gives off a positive charge, pH down (hydrogen ion) or a
negative charge pH up (hydroxide ion), and depending on the nutrient elements
being used, some carry more of the same charges than others. What’s more,
because of this it affects the pH of the surrounding root area and growing
medium. If it’s hydrogen ions being excreted, it becomes more acidic, and if it’s
hydroxide ions, it becomes more alkaline.

So it’s important to monitor the pH levels in your medium as well as your
nutrients and the alkalinity of water you are using. So how do you measure
your growing medium pH? Basically, there are three ways to do it:\

1. Saturated media extract – you add distilled or de-ionized water to the
medium just to the saturation point and measure.

2. Pour-through method – the water is poured through the pot to replace the
water that was in there and collected.

3. Squeeze method – the water that already exists in the medium is gently
squeezed out in a measured amount and pH readings are taken.

You don’t want to take your growing mediums pH readings from the top third of
your container because there usually isn’t enough root activity there. Instead
take your readings from the bottom two thirds of your growing medium where
the most root growing activity is to ensure an accurate reading.

More later.

It may surprise you to find out just how much activity is going on under the
surface of the growing medium. There is actually a lot going on there including
bacterial activity. Ever heard of Nitrification? This is a process that bacteria is involved
in. Nitrification is a process where specialized beneficial bacteria in your
growing medium take the urea and ammonium from the nutrients and convert
them into usable forms. Then the plant roots can absorb it and use it for plant
growth and development.

An important thing that happens in this process is that these beneficial bacteria
then give off an acid molecule which actually lowers your growing mediums pH
as well. And that’s a good thing. Now, if you have a pH that is too low,
nitrification will be inhibited. The same happens when your medium has too low
a temperature or there is a lack of oxygen through over-watering. Then the pH
goes up and the medium becomes more alkaline. Not good!

Now, you might have decided to make your own media mix. If so, alright. But if
you start with pure sphagnum moss, you will need to add at least 30% perlite
(between 30 – 40%) so that the sphagnum moss can breathe and aerate
properly, allowing the roots to pass through quickly and infuse into your growing
medium. When using sphagnum moss you could add 5 to 7% calcined clay to
increase the cation exchange capacity (CEC). This would help stabilize the pH in
that growing medium. I would not use calcined clay in a recirculating system
only in a “one way” feeding program. Of course, if you are new to hydroponics, I
would suggest you start by using Sunshine #4 mix, which has very good CEC
and is very forgiving. You will get a good crop even if you make a few mistakes.

There is something else that you might run into when mixing your own medium.
And that is inconsistent growing medium. The number one cause of pH problems
for growers mixing their own mediums is inconsistencies in source materials.
When mixing your own growing medium you need to know the sources of your
sphagnum moss and lime because they differ in pH from year to year and
locations. The only way to be certain you are working with the right pH
materials in your medium is to test it frequently. See “Laboratory Registry for
the United States and Canada 2nd Edition,” to get a comprehensive list of soil-
testing laboratories in the United States and Canada.

One thing to remember if you re-use your growing medium is that you may not
get consistent yields. You should be exceptionally cautious re-using your growing
medium if any of the following happens during your growing and flowering cycle:
your pH is currently running wild, you’re using a lot of limestone, not watering
regularly, or not leaching all the nutrients out at the end of your flowering cycle.
This is especially applicable to re-using sphagnum moss or coca coir. You might
want to store your sphagnum or coir from one crop to the next and, while the
other crop is growing, you can work with the stored medium to replenish it and
get it to the right pH level for the next crop.

Expanded clay pellets are many peoples choice for running hydroponics systems
because it’s easy to work with and cleans up easy for re-use. You can also re-use
perlite just sift it and clean it with very hot water or use a weak solution of
hydrogen peroxide and then rinse. The same can be done with expanded clay
pellets. If you’re using rockwool just throw it out after every crop. Though I’ve
seen and personally re-used rockwool, it’s a pain in the ass and I wouldn’t do it
because it has too many down sides. You’re better off buying it new. Here’s the
bottom line: you have to be interested in your growing medium’s pH and make
sure it’s clean if you’re going to re-use it to grow your plants. Otherwise, it will
be difficult for you to grow a consistently high-yielding, highquality crop. If you
don’t want to invest the time and money in this project, you’ll be better off to go
to your hydro store and get new growing medium for each crop.

Let’s have a look at how the different elements that make up your nutrients affect
your pH. We mentioned this earlier. Your nutrient
solution is made up of macro, micro and secondary nutrients. Macro means large
and micro means little. Macro nutrients are those elements like nitrogen,
phosphorus and potassium that your plants use a lot of. Micro nutrients, on the
other hand, are nutrients that are only needed in very small quantities like iron,
manganese, boron, copper, cobalt, molybdenum and zinc. Secondary nutrients are
calcium, magnesium and sulfur and are used in smaller amounts than macro
nutrients. All of these elements, macro, micro as well as secondary nutrients carry
either a positive charge (cations) or a negative charge (anions) and will effect the
pH of your growing medium as your plants use them up. In fact, most macro,
micro and secondary elements can be manufactured to carry more cations or
anions if a manufacturer is willing to go the extra mile and spend the additional
money required to have them custom made.

Cations include potassium, magnesium, calcium, zinc, copper, cobalt, manganese,
iron and ammonium. Anions include nitrates, phosphates, sulfates, carbonates,
bicarbonates. And different forms of these elements carry different amounts of
anions and cations.

Here's how it all comes together. Your plants roots take in both anions and cations
but when they do, different things occur. Like when the roots take in cations, they
give off a hydrogen ions-which are acidic-and is then released into your growing medium.
This makes your growing medium acidic and the pH is lowered. Now, when anions are
taken in by your roots, hydroxide ions are released which are alkaline and that raises
the pH of your growing medium. But as it goes, cations and anions actually work together.

Like I said, it's a balancing act.

The whole trick is to balance the cations and the anions; then you can maintain
the ideal pH in your growing medium. This does take a lot of work and research,
but it can be done. Why is this important? I’ll let you in on the secret. When you
use the cations in an ammonium based nitrogen source, it gives off acid
molecules and that helps to maintain the ideal pH around the roots and in your
growing medium. But when you use a mainly nitrate base nutrient, you are
working with anions which gives off alkaline molecules and that raises the pH.
This means you’ll need to continually adjust your pH down. Why do the extra
work when you can just maintain the right balance of ammonium and nitrates,
cations to anions, right from the start. And I don’t know for sure, but because of
this imbalance of anions to cations you may have a high pH in your growing
medium. And the worst part is, you aren’t even aware that this harvest robbing
culprit is lurking in your growing medium. Also, if you use a recirculating system
you’ll be continually adjusting your reservoir’s pH in an unending cycle of pH
balancing. And this directly affects the bigger yields that you could be getting.

So if a nutrient company actually cared enough, knew what they were doing
and was willing to spend the extra time and money they could make a perfectly
balanced nutrient solution that would keep the pH in the ‘sweet spot” in your
growing medium at all times. How would a nutrient company do that exactly?
First they would have to tune the cations and anions of all the elements in the
nutrient solution to a specific type of plant. And once you also knew what the
exact macro, micro and secondary nutrient ratios of that specific plant was...
You could then use your nutrient solutions nitrogen sources to help do the
“balancing” act for you, because nitrogen is abundantly used by your plant and
it is available in both cation (ammonium) and anion (nitrate) forms. Now we’re
getting some place. Only problem is, if you look at the hydroponics nutrients out
there most of them use only nitrate forms as their nitrogen source, which is an
anion form of nitrogen and drives your pH up in your growing medium as fast as
a speeding bullet.

When adjusting your reservoir’s nutrients to adjust your pH. For example,
potassium hydroxide (also called caustic potash) can be used to raise your pH up.
Use nitric and phosphoric acid to lower your pH down. You can use nitric acid in
your vegetative cycle because it will add nitrogen to your crop and phosphoric acid
in your flowering cycle because it will add phosphorus. And guess what? Personally
I prefer to use nitric acid in my flowering cycle because tissue samples have shown
your favorite plant doesn’t use a whole lot of phosphorus during flowering. In fact,
in most cases nitrogen use increases. If you’re looking for organic forms of pH
down you can use citric acid to bring the pH down. This you can get at a vitamin
store; just make sure that it is a really pure type of citric acid. You can even use
vinegar (acetic acid) but the acetic acid varies in different vinegars so you have to
be a bit more careful and watch what goes on. For this reason, citric acid is the
preferred acid to use.

Some companies promote using chemicals to buffer your hydroponics nutrients.
So what is a buffer? A buffer is a chemical that helps maintain pH stability of the
nutrient solution. A lot of growers aren’t aware of this little known fact, but a lot
of nutrient companies use magnesium, calcium and potassium carbonate or
bicarbonate as their pH buffers. This is absolutely not a good idea. Here’s why:
remember that carbonates and bicarbonates are anions and add to the alkalinity
of your nutrient solution and growing medium, and even though they might
buffer the pH a bit, these “down and dirty” pH buffers will cause your growing
mediums pH to accelerate up.

It all matters.

-Shrubs-