The Importance of PH - Lesson 13

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The importance of pH. pH stands for potential hydrogen ions positive and negative. Essentially, it’s the measurement of the alkalinity or acidity of a given substance.

This is measured on a scale from 0 to 14, 7 being neutral. Anything above 7 is alkaline; anything below 7 is acidic. How does it relate to plant growth?

Nutrients are more or less available at different pHs. For our purposes in general, we could say that our plants like a slightly acidic root zone, so that’s a 6, 6.2. Sometimes people become really uptight about pH. They think that it has to be exactly 6.2 all the time.

Now there is some flexibility in this and we’re going to discuss that, and it can relate to different gardens like let’s consider first a drain waste garden. Let’s consider a peat-based garden. Now peat is naturally acidic, a 4 actually, and it is lime that keeps the pH at an acceptable range, otherwise the peat will be far too low for our purposes. When you buy a bail of peat mix, it has been limed, and that is what gets pH up to 5.8 or 6.

As you water that medium, you’re actually washing the lime out and the acidic nature of that peat can start to take over. If you don’t re-lime like the lime is what we call the buffering agent. It has the ability to actually drag the pH towards neutral and hold it there as opposed to a pH adjuster like your pH up and down in which you are simply adjusting your nutrient solution. It has no buffering capacity, so you can adjust your nutrient solution and pour it through your peat mix, but you will only temporarily adjust the pH.

In order to have a lasting effect, you have to use a buffering agent like lime, oyster shell flour, dolomite, some type of lime. It is often quite necessary to lime your medium, the peat-based medium throughout the crop in order to keep the pH in an acceptable range.

Sometimes what happens to people, they don’t know this. By the time, they notice that something is going wrong with their plants, it’s going to appear as nutrient deficiencies because essentially the pH becomes more and more acidic so certain nutrients like calcium are not as available. We start to see a limit in nitrogen uptake due to the unavailability of the calcium, and before you know it by the time the client checks his runoff pH, he finds out that he’s at 4.8, in which case there is no way that any buffering agent can pull him out of that in the crop. He is going to experience severe losses.

We definitely want to be proactive and control the pH of our peat-based mediums before they plummet to unacceptable levels because the way the pH skill works, every point that you depart from the neutral point is 10 times harder or more powerful so every point you go away is going to require 10 times the amount of adjuster. That’s why you want to get these problems before they become too extreme.

Now in a re-circulating hydroponic garden where we do not have any medium and no buffering agents, whatever we mix the nutrient solution at is what we’re going to see in the garden. It is possible to allow the plants to drift the pH up and down without experiencing any real losses. Plants will actually secrete acids and bases from their root zone and adjust the pH of the nutrient solution in their reservoir based on the nutrients that they want to eat.

Let’s say the plant wants more calcium and magnesium. It may actually expend energy to secrete a base in the root zone, raise the pH, make the calcium more available, so it can take up more of it. If we’re constantly in there with our pH down, dropping it to 5.8 every single time it raises a little bit, we’re actually fighting against the plant. We can allow a little bit of drift.

Having said that, if you go below 5.8 in a recirculating hydroponic garden, your environment is getting very acidic, and that is going to allow Pythium root disease to really take off, so that’s a very important danger line. We want to see our pH – it can drift between 5.8 and 6.4, even up to 7. It’s not going to create any kind of problem in your garden. If we allow an acidic environment to persist, then we will see major problems with root disease, which is the number killer of yield in hydroponic gardens.

Gardening is a passion for many of our customers. We believe the escape into a garden can be a great stress reliever.

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