In the latest issue of ROOTS magazine, we discussed the importance of soil pH control, especially for those who plant plants near forests or simply elsewhere than in their gardens. We also talked about the possibilities of pH control in the soil and its adjustment using easily available means. We are now moving to the second part of pH control, namely the pH control of water. 


We already know that the right pH level will ensure that plants reach the necessary elements more easily, and therefore their metabolism will improve and they will benefit better overall than if the pH value is not controlled. 

First of all, it is necessary to say that the pH of the water is checked significantly more often than it is with the soil - ideally with every watering. For this reason, it is also much better to choose instruments for faster and more accurate measurements, which will save us a lot of time.

But to really start from the beginning, we should ask ourselves what the whole testing process should look like. 

We always use standing water for watering plants for at least 24 hours - this is especially true in the case of tap water, which contains chlorine, which we get rid of thanks to standing. The second thing is the temperature - ideally the water for watering should be at room temperature. Ideally, between 20-22 ° C, this guarantees us the highest nutrient intake and the minimum possibility of root mold. 

After we have water, and if we have fertilizers, their time comes. We add fertilizers according to the recommended dosage from the manufacturer, or if we have an EC meter, then the required EC, and mix properly. The vast majority of fertilizers affect the pH in some way, either up or down. If we are not going to fertilize and we are just giving clean water, we will of course skip this step. 

At this point, we measure the pH using the required indicator or instrument. As for the pH of the watering for the soil, the ideal value is between pH 6-6.5. In hydroponics, ie aeroponics, these values are lower and range between pH 5.8–6.3. 

If the values are at levels other than these, it is time to adjust them. This is done differently from the soil, using acids to lower the pH values or bases to increase them. Acids and bases for adjusting the pH of water are, in the vast majority of cases, liquid, with only one exception, which we will discuss below.

Tap water, as well as well water, is usually alkaline, so many more growers need to lower the pH. 

The first and most common option for lowering the pH is to use phosphoric acid. This can be found in grow shops, in various concentrations for different needs of growers. It is extremely clear that a grower who needs to mix 200 l of watering will reach for higher concentrations, and conversely, a grower who is watering, for example, 10 l of watering, will reach for a lower concentration to make the pH correction as accurate as possible. Phosphoric acid is thus available in concentrations from 25 % to 70 %. 

Phosphoric acid is usually referred to as pH down BLOOM, ie as an acid to lower the pH in the flowering phase. The reason is that until last year, nitric acid, referred to as pH down GROW, was also available to reduce pH. However, it was banned because nitric acid was also used to make bombs… So growers also paid for the whole terrorist situation in recent years. 

Another way to lower the pH of water is citric acid. However, I do not recommend using lemon. However, there are companies that have slightly altered citric acid to make it a stable alternative to lowering pH. However, what needs to be noted for hydroponic growers is modified citric acid in powder form. This pH adjusting product, although not the cheapest, is definitely more unstable in the long run. We recorded stable values of pH values in flow systems, bubblers and aeroponics without as frequent adjustments as in the case of liquid acids. 

If you belong to a minority of growers and your pH is low, you will reach for the principles. These can be found in two versions, as hydroxide or as humic acid for BIO cultivation and soil cultivation. 

As for the treatment itself, I always recommend using a pipette or syringe and dosing the acids or bases in small doses so that it is not necessary to use means to lower or raise the pH at the same time.

An absolutely ideal way to speed up the measurement is to take notes. This may look like you first measure the pH of your inlet water. Then add the fertilizer and record the pH value. You adjust the pH to the desired value and record the dose of acid or base again somewhere. With these notes, if you repeat the amount of watering with the same amount of fertilizer, you will know exactly how much pH adjuster to add. 

In any case, it should also be said that the pH values change over time, which means that if you mix a dressing with an ideal pH in one day, the pH values may be different the next day - this is especially true for dressings that contains fertilizers.  

The pH of water is measured in the same or very similar ways as the soil - using paper strips, liquid pH testers and electric pH meters. However, the whole testing process is much simpler. Simply soak the strips in the test sample and compare the color of the strip with the color scale included in the package. It is just as easy to use a liquid pH tester, into which you just need to pour the test sample, add 3 drops of indicator liquid and compare the color of the sample again with the color scale. As for electric pH meters, it is definitely appropriate to say something more about their use, as they are used more often, and if we want to have accurate results and ensure a long life of the device, we should know more about them. 

Unlike electric pH meters in the soil, they have a glass probe for measuring the pH of water, which needs to be taken care of, otherwise their service life is significantly shortened. The first and most important step in extending the life of pH meters is to use a storage solution. After the measurement, it is poured into the lid of the pH meter. After about half an hour, we can observe that the solution crystallizes and envelops the probe - this protects the probe. 

The next step to accurate measurement and prolong life is also regular calibration. This is done depending on the type of device. The vast majority of instruments have one-stage or two-stage calibration. At the very least, you can also encounter instruments that have a three-stage calibration - but these are mostly used mainly in chemistry. 

The number of calibration steps indicates how accurate the instrument is. When growing plants, we do not have to treat in thousands, so a one-step calibration is enough. The calibration goes through steps 4.01, 7.01 and 10.01, respectively. However, the most commonly used calibration is 7.01. 

We recognize 2 types of calibration, either manual or automatic. When automatically calibrating the pH meter, the desired degree of calibration will appear on the display - at that moment you will insert the probe into the calibration solution with the appropriate pH value (4.01, 7.01, or 10.01). For manual calibration, it is necessary to first immerse the pH meter probe in the calibration solution and then, using the screwdriver included in the pH meter package, gradually adjust the pH value according to the calibration solution in which the pH meter is located. 


"We always use standing water for at least 24 hours to water the plants"

"The absolute ideal way to speed up measurements is to take notes"