The important role of pH and EC levels in hydroponic plant growth.
Hydroponics is a modern method of growing plants without the use of soil, as a nutrient solution is delivered directly to the roots of plants. The pH and EC levels of the solution play a crucial role in providing you with information on the nutrients available to the plant. This information is important to successfully grow a plant in a hydroponic system.
What is pH?
pH stands for potential hydrogen. The pH value is a measure of how acidic the nutrient solution is. The pH value is measured on a scale of 0 to 14, with 7 being considered neutral. Values below 7 indicate acidity and values above 7 indicate basicity. The pH levels indirectly measure the availability of nutrients to the plants, leading to potential nutrient deficiencies or toxicities. Knowing the pH level will indicate to you whether you need to add more nutrients or not.
What do the levels of pH need to be?
The optimal level of pH varies per plant. You can find the optimum pH level for specific plants in the table below. Overall, the pH range for most plants is optimal between 5.5 – 6.5. In the picture above you can find different nutrients and their availability by pH levels. This range is the most optimal as it allows the roots of the plants to absorb the nutrients they need effectively. To maintain the ideal pH range in a hydroponic system, it is essential to regularly monitor and make adjustments if necessary. The pH level can be measured with a pH meter or pH paper. This is an electronic device that measures acidity and gives accurate, and quick results.
How to deal with a pH that is too high or too low?
Maintaining the correct level of pH is important for a healthy hydroponic system. When the pH is too high, you can lower it by adding an acid such as phosphoric acid, citric acid or vinegar. In the case of a low pH, you can raise the pH level by adding a base such as baking soda. Nutrients like potassium, hydroxide or calcium that are present in hydroponic nutrients also increase pH. It is important to measure pH regularly, as fluctuation can occur due to nutrient uptake. Each plant has its optimal pH range, these can be found in the table below.
What is EC?
EC stands for Electrical Conductivity, which measures the concentration of dissolved salts and minerals in a nutrient solution. It is measured in units of millisiemens per centimetre (mS/cm). The concentration of dissolved salts in the solution can affect the availability of nutrients for the plants.
Plants require various minerals and nutrients to grow and develop, including nitrogen, phosphorus, potassium, calcium and more. These nutrients are provided in the nutrient solution. See the link to our nutrients: Shop. The concentration of nutrients in the water needs to be carefully controlled to ensure that they are available in the correct amounts for the plants you are growing.
What do the levels of EC need to be?
The ideal EC level for a hydroponic system varies depending on the stage of plant growth, the type of plant and the nutrient solution. Generally, the EC level needs to be in between the ranges of 0.8 to 2.5 mS/cm. In the case of a low EC level, the plants may not receive enough nutrients to grow and develop properly. On the other hand, a too high EC can lead to nutrient toxicity. To maintain the ideal EC level, it is important to test the nutrient solution regularly using an EC meter and adjust the nutrient concentration as needed. Below you can find a table with an overview of the best EC and pH levels per plant.
How to deal with EC levels that are too high or low?
The EC displays the electrical conductivity of the water. This means that it does not specifically display the amount of each nutrient in the mix. When the EC is too low, you can add more nutrients to the mix in order to increase mineral content. A low EC level does not damage the plant immediately but will slow down the growing process. If the EC level is too high, you can simply dilute the EC level by adding more water. Keep in mind that the EC-level does not specifically show the amount of specific nutrient shortages, which might lead to an overload of another nutrient. When problems keep arising regarding the EC it is sometimes the best to empty the container and refill it with new water and nutrient mix so you are sure all the minerals are rebalanced again. The mixing instructions can be found via the following link: Mixing Instructions.
Conclusion
The success of a hydroponic system depends on the pH and EC levels of the nutrient solution. The pH level measures the acidity or basicity of the solution and should be between 5.5 – 6.5 for most plants. The EC level measures the concentration of dissolved salts and minerals and should be between 0.8 – 2.5 mS/cm. Monitoring the pH and EC levels can be done with pH and EC meters, it is essential to do this to ensure that the plants receive the right amount of nutrients for optimal growth.
Below a table is shown with several plants and herbs and their optimal pH and EC level when being grown in hydroponics systems.
| Plants | pH level | EC level |
| Brocolli | 6.0 – 6.8 | 1.4 – 3.5 |
| Courgette | 5.5 – 6.5 | 1.8 – 2.4 |
| Cucumber | 5.5 – 6.0 | 1.6 – 2.5 |
| Eggplant | 5.5 – 6.5 | 1.8 – 3.5 |
| Garlic | 6.0 – 6.5 | 1.4 – 1.8 |
| Kale | 5.5 – 6.5 | 1.2 – 1.5 |
| Leek | 6.5 – 7.0 | 1.4 – 2.0 |
| Lettuce | 5.5 – 6.5 | 0.4 – 1.4 |
| Peppers | 5.8 – 6.5 | 2.0 – 3.5 |
| Bell peppers | 6.0 – 6.5 | 2.0 – 2.5 |
| Hot peppers | 5.5 – 7.0 | 1.0 – 2.0 |
| Bok choy | 6.0 – 7.0 | 1.5 – 3.0 |
| Spinach | 6.0 – 7.0 | 1.8 – 3.5 |
| Strawberry | 5.8 – 6.2 | 1.4 – 3.0 |
| Tomato | 5.5 – 6.5 | 2.0 – 5.0 |
| Zucchini | 5.5 – 6.5 | 1.8 – 2.4 |
| Herbs | pH level | EC level |
| Basil | 5.5 – 6.5 | 1.0 – 1.6 |
| Chives | 6.0 – 7.0 | 1.8 – 2.4 |
| Cress | 6.0 – 6.5 | 1.2 – 2.4 |
| Mint | 6.5 – 7.0 | 1.0 – 1.4 |
| Sage | 5.5 – 6.5 | 1.0 – 1.6 |
| Parsley | 5.8 – 6.5 | 0.8 – 1.8 |
| Thyme | 5.5 – 7.0 | 1.2 – 1.6 |
