Hydroponic Gardening with Coconut Coir in a Drain-to-Waste System

Hydroponic gardening offers an efficient and controlled method of cultivating plants, and using coconut coir as a growing substrate in a drain-to-waste setup can yield excellent results. In this article, we will explore the importance of run-off in drain-to-waste hydroponic systems, how to utilize run-off to monitor root zone conditions, pH and EC considerations, as well as the necessary calcium and magnesium supplementation when using coconut coir as your growing medium.

Importance of Run-Off in Hydroponics

In a drain-to-waste system, run-off refers to the excess nutrient solution that flows out of the growing container after irrigating the plants. Collecting and analysing run-off is crucial for maintaining optimal root zone conditions. It provides valuable insights into the nutrient uptake and pH stability within the root zone, helping to prevent nutrient imbalances or deficiencies.

Using Run-Off to Monitor Root Zone Conditions

  1. Collecting Run-Off: Place a tray or container beneath the plants to capture the run-off. After irrigation, allow sufficient time for the excess nutrient solution to drain out. Collect a sample of the run-off for analysis.
  2. pH Monitoring: Measure the pH of the run-off using a pH meter or test strips. The ideal pH range for most plants in hydroponics is between 5.5 and 6.5. If the pH of the run-off deviates from this range, adjustments can be made to the nutrient solution to bring it back into the desired range.
  3. Electrical Conductivity (EC) Monitoring: Measure the EC of the run-off using an EC meter. EC indicates the concentration of dissolved salts in the root zone. Monitoring EC helps identify if the plants are receiving an appropriate nutrient concentration. Adjustments to the nutrient solution can be made based on EC measurements.

pH and EC Considerations

  1. pH Adjustment: Coconut coir has a slightly acidic pH, so it is important to monitor and adjust the pH of the nutrient solution accordingly. Regularly test the pH of the nutrient solution before irrigation, and make necessary adjustments using pH up or pH down solutions.
  2. EC Control: Coconut coir has some natural cation exchange capacity, which means it can hold onto nutrients. However, it is important to maintain the desired EC level in the root zone. Measure the EC of the nutrient solution and adjust accordingly to ensure plants receive an appropriate nutrient concentration.

Cal-Mag Supplementation in Coconut Coir

Coconut coir is a great growing substrate that provides your plants developing root system with abundant access to air whilst simultaneously holding plenty of water and nutrients, but it tends to retain calcium (Ca) and magnesium (Mg) due to the strong double bonds these ions form with cation exchange sites within the coconut coir. To prevent potential nutrient deficiencies in your hydroponic crop, it is necessary to supplement your nutrient solution with additional calcium and magnesium.

  1. Calcium Supplementation: Use a calcium-rich nutrient solution or add a calcium supplement to the nutrient mix. Monitor the EC and pH after adding the supplement.
  2. Magnesium Supplementation: Magnesium sulfate (Epsom salt) is commonly used to provide magnesium supplementation in coconut coir. Dissolve magnesium sulfate in the nutrient solution according to the recommended dosage. Monitor the EC and pH after adding the supplement.

Many nutrient companies produce a Cal-Mag supplement product specifically designed to account for the calcium and magnesium ion holding properties of coconut coir, which removes the additional hassle of calculating and formulating your own supplement solutions.


Hydroponic gardening with coconut coir in a drain-to-waste setup offers an effective method for cultivating plants with optimal growth and yields. Monitoring run-off, pH, and EC levels allows growers to maintain a healthy root zone and prevent nutrient imbalances. Additionally, supplementing with calcium and magnesium ensures the plants receive the necessary nutrients. With proper attention to these considerations, hydroponic gardeners can enjoy successful and thriving gardens using coconut coir as their chosen growing substrate.