pH in Hydroponics: Importance And How To Keep pH Stable In Hydroponics

When starting out with hydroponic growing, you will probably learn about important factors for growing plants such as light, distance, nutrients, hydroponic growing medium, etc. for your plants. But there is one more important factor that you absolutely should not forget: the pH for hydroponics. If the pH is too high or too low, plants cannot absorb nutrients and grow well.

Read the article below to understand more about the important role of pH as well as how to keep pH stable in a hydroponic to help plants grow healthy.


Why is pH for hydroponics important?

The pH in a hydroponic growing medium is directly related to the ability of plants to absorb essential nutrients. At too high a pH, micronutrients are absorbed at toxic levels while macronutrients are lacking. Conversely, an alkaline pH can prevent nutrient absorption and lead to deficiencies.

With plants grown in soil, pH level is naturally controlled as minerals in the soil interact with water buffer variations and through nutrient cycles.

However, for a hydroponic system, you need to monitor and adjust the pH level to create an environment that is most beneficial to the plants.

An environment with the appropriate pH will allow plant roots to absorb the nutrients they need. However, each plant has different nutrient requirements, so pH levels vary, you need to keep this in mind.

Some typical hydroponic pH level for perfectly grown plants

As mentioned above, each plant has a different nutrient requirement, so the hydroponic pH level will also be different for the plant to grow stably.

Normally, hydroponic plants usually have an optimal pH range of 5.5 – 6; this applies to most fruits and vegetables like parsley, tomatoes, beans, melons, apples, etc. However, to get the best effect, you also need to know the pH range of each plant to be able to apply and adjust the most suitable pH.

Let’s refer to some types of hydroponic plants below to know more information:

Fruit crop Ideal pH Range Vegetable Crop Ideal pH Range
Apple 5,0-6,5 Broccoli 6,0-6,5
Melon 5,5-6,0 Cabbage 6,5-7,0
Cantaloupe 6 Carrot 6,3
Strawberries 5,5-6,5 Cauliflower 6,0-7,0
Watermelon 5,5-6,0 Cucumber 5,5-6,0
Grape 6,0-7,5 Eggplant 5,5-6,5
Mango 5,5-6,5 Kale 6,0-7,5
Pineapple 5,5-6,0 Lettuce 5,5-6,5
Raspberries 5,8-6,5 Peppers 5,5-6,5
Blueberry 4,0-5,0 Tomato 5,5-6,5
Plum 6,0-7,5 Potato 5,0-6,0
Peach 6,0-7,5 Squash 5,0-6,5

The pH of each hydroponic growing medium

Each hydroponic growing medium has a different pH range, which is suitable for each different plant, but not everyone knows how to use the most effective hydroponic growing medium, so you need to carefully research and understand the information of the substrate from the instructions provided by the manufacturer or supplier before using:

    • Sawdust – Acidic
    • Peat – Acidic
    • Rice hulls – Neutral / Acidic
    • Sand – Neutral
    • Mineral wool – Basic
    • Expanded clay – Neutral
    • Coco coir – Neutral

As mentioned, pH for hydroponics is usually between 5.5 – 6 which is considered optimal for hydroponics. Among the hydroponic growing medium listed above, the most prominent and most used in hydroponic growing is coco coir.

So why is coco coir an effective growing medium for such a hydroponic system?

Because coco coir holds water exceptionally well and at the same time provides proper drainage. The pH of coco coir in the range of 5.8 – 6.5 is very suitable for many crops.

Moreover, coco coir is 100% natural and does not contain pathogens due to being thoroughly pasteurized, so it is considered as an effective substitute for soil.

To understand the characteristics of coco coir as well as why coconut coir is suitable for hydroponics, you can refer here.

What causes pH changes in a hydroponic system?

There are many factors that affect the change in hydroponic pH levels, but the main cause is the absorption of nutrients and water from the plants. Since pH is based on concentration levels, reducing the volume of water under a gallon will cause the solution to become more concentrated as the plant absorbs nutrients. This results in high fluctuating pH levels. Therefore, it is necessary to monitor the nutrient solution level, keep the reservoir full, and regularly check the pH in the reservoir.

Another factor is the buffer of the growing medium. Both inorganic and organic matter can affect the pH levels in a hydroponic system. For example, gravel and other inorganic media act as a buffer and cause the pH to rise in media-based systems. In the natural environment, soil acts as a buffer in a similar way. For accurate pH values ​​in a substrate-based system, immerse the inorganic medium in a weak acid to neutralize the acid and vice versa.

pH fluctuations can also come from organic properties such as bacteria and algae. Keeping the solution slightly acidic, observing root health, and removing decayed roots will combat this problem.

How to keep pH stable in hydroponics

Regularly test the pH level

Regular monitoring and testing is the first step to keep the pH stable in hydroponics. There are many ways to test pH levels such as using pH test strips, pH test solutions, or pH meters. But to be effective and not take the most time using a pH meter.

This tool will help you test and adjust the pH level of the solution until it is within the range you desire.

When measuring with a pH meter, it is recommended to use distilled or purified water instead of tap water, as it is possible in tap water to have its pH.

If the pH isn’t exactly what your plants want, use the right nutrients based on the pH range of the media your hydroponic plants require.

Coco coir

It is no surprise that coir is mentioned here.

If you are starting out with hydroponic growing, you may be wondering what makes coco coir so good at keeping pH stable in a hydroponic growing system!? First of all, coco coir has unique cation exchange sites.

This means that coco coir is easily broken down when other nutrients get into the mix. It also means that in a growing medium containing potassium or sodium content, coco coir will release them.

This is a beneficial feature for plants, as it prevents excess potassium from accumulating in the root zone.

To make the best use of coco coir in hydroponics, add a small amount of buffering agent to it. The buffer can be a few millimeters of perlite into the coir bag.

Another important factor that helps coco coir to keep pH stable in hydroponics is the pH of coco coir in the range of 5.8 – 6.5, this is a concentration suitable for most hydroponic crops.

Once you have the suitable pH in place, it’s time to supplement your plants. This will allow hydroponic plants to get the best start in their hydroponic growing medium.

Increasing buffering capacity

Another popular way to keep pH stable in hydroponics is to use nutrient solutions to buffer the solution or medium and keep it within the desired pH range.

If you’re using natural media, the pH of your water will also affect the pH of your media. You need to adjust the pH level of the water depending on the type of medium you are using.

If the hydroponic pH level of the medium is high, you can add a small amount of vinegar to the water to lower the pH level.

If the pH of the hydroponic growing medium is too low, you can add lime water or kalkwasser to increase the pH. Kalkwater contains calcium carbonate, which converts to calcium bicarbonate when exposed to high pH levels. This will help raise the pH of your environment.

Finally, once again, one thing you need to keep in mind is that you need to regularly test the pH as this will help you detect and monitor it in time to help you keep the pH stable in hydroponics.

How to know if plants need more or fewer nutrients in a hydroponic system?

Not all the same, but in general, one way to know if your plants need more or fewer nutrients in hydroponics is to compare their actual growing conditions.

For example, a lack of nutrients will lead to the yellowing of leaves and vegetation, while too much will lead to browning.

Another check you can do is examine the root system with a magnifying glass. If you see small holes in the roots that look like small cuts or scrapes, this means they are being watered a lot and have plenty of oxygen.

Besides, if there is an overgrowth of moss on the root tips when the plants are in a high-nutrient solution for a long time, they may not get enough nutrients, water, or oxygen.

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