Nutrient Monitoring: How To Do The PourThru Test

The Leachate PourThru Test Method is a great way to monitor nutrition during the growing season. Leachate is simply the water that flows through the soil and out of the bottom of a pot. This drainage water can provide an indicator of soil conditions and can tell you things like if there is too much salt in your soil. This is a simple test that is great to incorporate into your nutrient program and will ensure your nutrients are not being used in excess and creating a toxic environment in the soil.

How to do The PourThru Test

  1. Designate particular plants that will be used for sampling
  2. Get a sample of your substrate into a pot
  3. Pour water in from your water source, and collect the water in a container for testing
  4. Send sample to a lab, or do your own testing using a pH and EC meter
  5. Record the results to build up a history you can use for comparison and future harvests

Pro Tips for PourThru Testing

  • If you are watering plants with alkaline water that is over 150ppm, use distilled water when you do PourThru testing.
  • Water plants at least 1 hour before collecting samples, then apply enough water to get 50ml of leachate.
  • Do not collect more than the first 50ml of leachate or your sample will be diluted and inaccurate!

Why do The PourThru Test?

Monitoring nutrient levels is very important. In order to ensure that you are maintaining proper levels, you need to do PourThru testing. If you are not monitoring nutrient levels you can run into some very unwelcome surprises like nutrient deficiencies. Another possibility is that you are wasting nutrients by overusing them. If you regularly monitor nutrient levels you can detect irregularities before they become a bigger problem. For example, if you detect excess salt accumulation you can flush plants and decrease nutrient solution concentrations before plants show signs of damage. If you wait until you see the visible deficiency signs, the plant will likely already be damaged. Even if you can save the plant at that point it will not be as productive as a plant that did not become visibly damaged.

When Should I do The PourThru Test?

The PourThru Test should be performed weekly. You may want to do it more often when working with a new nutrient line, new strain, or are transitioning to a new growth stage. If you are growing in hydroponics, you need to monitor pH and EC daily (or with continuous monitoring devices). For growing in soil or other potted plant mediums, weekly is the best option though. You should test at least five pots from each crop/strain individually. Be sure to take some from the center and outside areas so you get a sampling of plants from different areas of your cultivation space. You may find that plants in certain locations need slightly different nutrient and irrigation treatments than plants in other locations.

Interpreting Results of a PourThru Test

You'll need to adjust your nutrient solution or perform flushing to correct nutrient conditions based on the results of the PourThru test.

PourThru EC Result
0 to 1.0 mS/cm Very Low
1.0 to 2.6 mS/cm Low
2.6 to 4.6 mS/cm Normal
4.6 to 6.5 mS/cm High
6.6 to 7.8 mS/cm Very High
More than 7.8 mS/cm Extreme
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