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What is Runoff and How do I Check it?

Runoff is the collection of a nutrient solution after it has passed through the substrate of a plant. In a potted plant, a plastic dish or tray is placed underneath the container to collect the excess nutrient solution that has passed through the container holding the root zone. This runoff solution is regularly tested for pH and EC to determine if changes need to be made to our next nutrient feeding.

EC PPM meter

Tips for analyzing and collecting runoff:

  • The first thing to understand is all nutrient lines are different. Every nutrient line has a unique set of ingredients, organic additives and elemental ratios that all play a role in the overall EC of the nutrient solution. Just because you successfully feed 3 EC with one nutrient line doesn’t mean 3 EC should be your target with another. EC is not a universal measurement between different lines and the substrate management we will talk about on our website relates directly with the Perfect Grower line of nutrients.
  • Make sure your plants never sit in their runoff. If you have collection dishes under your pots, do not let the plants reabsorb this solution. Runoff is for testing purposes and should always be kept away from the root zone.
  • Make sure your tables, dishes or anything else that touches your runoff solution is clean. If you have salty or crusty trays, it’s very easy to get inaccurate readings. If the runoff readings are inaccurate, we will make incorrect decisions for our next feeding.
  • It’s a good idea to check runoff from different areas. You don’t need to test runoff from every single plant in your growing environment but it’s wise to collect runoff from similar groupings, like genetics or substrates. Combine the runoff from a few plants in each group and test the average with your meter. You will find out that different genetics can accumulate much faster than others, even in the same room.
Updated on November 11, 2019

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