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pH in Hydroponics: How to Maintain the pH Levels of Hydroponic Systems



You can hardly wait to get started with your hydroponic system. You’ve researched light, spacing, and nutrient requirements for your plants. Don’t forget one of the most important factors in hydroponics: pH levels. If the pH level is too high or too low, plants cannot absorb nutrients and will not thrive in otherwise ideal conditions.  Read on to learn the role of pH in hydroponic systems and how to properly monitor and maintain its levels.

A pH test shows whether a substance is acidic or alkaline. The pH scale ranges from 0 to 14, with 0 being the most acidic, 14 the most alkaline, and 7 is the pH-neutral point. Some plants prefer acidic conditions while others require an alkaline environment. There are many methods available for testing and adjusting pH levels in hydroponic systems.

Why pH is Important in Hydroponic Systems

The right pH level is crucial because it affects nutrient availability for your growing plants. A pH level that is too high or alkaline can prevent nutrient uptake and lead to deficiencies. Iron deficiency causes pale or yellow leaves in young plants, while leaf cupping and tip burn are telltale signs of calcium deficiency. Calcium can also form salts that leave white deposits or scale on reservoir walls and equipment.

Hydroponically grown plants need different pH levels than plants grown in soil. Without soil, plants do not benefit from microorganisms, organic matter, and interactions between water and minerals that regulate pH levels. The hydroponic gardener must constantly monitor and adjust pH levels. Make sure that you do not apply pH recommendations for soil-grown plants to hydroponically grown plants.

Typical pH Ranges for Crops

With some exceptions, the optimal pH range for hydroponically grown crops is generally between 5.5 and 6. Many fruits and vegetables, such as melons, apples, beans, squash, and tomatoes prefer that range. Blueberries, on the other hand, need a lower, more acidic pH between 4.0 and 5.0. It’s a good idea to use separate nutrient reservoirs for plants with similar pH ranges.

Some hydroponic crops have a wide optimal pH range. Pumpkin, for example, will thrive in a pH between 5.5 and 7.5. Crops that require alkaline conditions include kale, onions, and peas, which prefer pH levels between 6.0 and 7. Mint plants tip the scale at an optimal pH range of 7.0 to 8.0.

Typical pH Ranges for Nutrient Systems

Hydroponic nutrient products typically start with pH levels between 5.5 and 6.0, the optimal level for most crops. The pH range, however, depends on the specific formulation. For example, ammonium nitrate has a more acidifying effect than nitrate and will cause a drop in pH. Calcium salts, on the other hand, cause a rise in pH, resulting in a more alkaline solution.

Specific nutrients require certain pH levels for plant uptake. The wrong pH level can result in too little or too much of certain nutrients. For example, when the pH level drops below 5.0, plants can develop magnesium and calcium deficiencies or copper and iron toxicity. A pH level above 6 or 6.5, however, can cause iron deficiency.

Why pH Levels Change in Hydroponics Systems

Several factors can cause pH levels to change in hydroponic systems. When the amount of the nutrient solution drops below one gallon, the solution becomes more concentrated as plants absorb the nutrients. This results in widely fluctuating pH levels. It is, therefore, important to monitor nutrient solution levels, keep the reservoir full, and regularly test the pH in the reservoir.

Both inorganic and organic matter can affect pH levels in hydroponics systems. For example, gravel and other inorganic growing media act as a buffer and cause pH levels to rise in media-based systems. In a natural environment, soil acts as a buffer in a similar way. To get an accurate pH reading in a media-based system, test the pH of the reservoir solution as well as the solution (leachate) that drains from the beds or bags that hold the plants.

Algae and bacteria are the main types of organic matter that affect pH levels. If pH levels rise in the morning and drop later in the day, algae may be the culprit. As algae consume acidic carbon dioxide during the day, pH levels rise and then fall by evening. On the other hand, bacteria from root disease can cause a dramatic drop in pH levels. As diseased roots decompose, bacteria will release acids into the hydroponic solution.

How to Maintain the Right pH Levels

The first step in maintaining the right pH levels is testing. A variety of testing supplies are available. Test strips and liquid test kits are the least expensive and are available at pool supply stores and garden centers. Digital pH meters are more accurate and offer repeatable results. You should test frequently with whatever hydroponic testing instruments you choose, even daily if you have recently adjusted nutrient levels or have little experience with hydroponics.

If you use a recirculating system, adjust the pH level according to test results from the supply reservoir. In a media-based system, however, the pH changes as the nutrient solution travels from the supply reservoir and out through the grow base. Adjust pH levels based on the pH of the leachate that drains from the grow beds.

Commercially prepared “pH up” and “pH down” products are available to maintain the right pH levels. You can purchase these products in dry or liquid form and use them according to label instructions. Make sure you use products that are formulated for hydroponic systems. For small systems or short-term results, you can add weak acids such as vinegar or citric acid.

Automatic pH controllers cost more than pH up or pH down products but they keep the pH at consistent levels. This option works best in recirculating systems to prevent pH fluctuations that occur as plants feed.

If your water is hard, the buffering effect of the high mineral levels will cause high pH levels. A reverse osmosis system is an efficient and relatively affordable method for reducing water hardness.

Benefits of Measuring and Maintaining pH Levels

Each plant needs certain growing conditions to thrive. It’s worth the time and effort to monitor and adjust pH levels in hydroponic systems. If you know the optimal pH ranges for your plants, you can take the necessary steps to keep your hydroponically-grown plants healthy.

To learn about Jenco’s wide array of pH meters and testers, browse our products or reach out to us to discuss your unique needs and challenges with a Jenco representative.  

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