EC 101: A Cannabis Cultivator's Guide

EC (Electrical conductivity) & PPM (Parts Per Million): 

  • What is it? 
    • EC is the world-wide standard of measurement to determine the concentration of nutrients in your reservoir. EC measures the levels of nutrients in your system, you can test your EC  by doing a runoff test.


What’s the difference between TDS and PPM?

  • TDS stands for Total Dissolved Solids and PPM stands for Parts Per Million. TDS is measured in PPM. Some companies use a 700 scale for PPM while others use a 500. Future Harvest uses the 500 scale. 

What scale does Future Harvest use?

  • EC is measured in microSiemens that we have converted to a .5 scale. 
  • PPM is measured in a 500 scale.



What is the difference between EC and PPM? 

  • EC measures the levels of nutrients in your system, you can test your EC by doing a runoff test. PPM measures the amount of nutrients in your growing medium. PPM meters use two different conversion rates depending on your meter. 


Why is EC important?

  • Too low an EC and your plants will lack the nutrients they need. 
  • Too high an EC can lead to nutrient lock-out with the high level solutes in the media. This can cause inhibited water intake through the roots. 


Most crops prefer an EC within the ranges of 1.5-2.5 

  • EC measures  the concentration of dissolved salts in the nutrient reservoir by milliSiemens per centimeter (mS/cm) or microSiemens per linear centimeter (mS/cm).  




EC Damage - what to look for:

  • Light-green color on new leaves
  • Edges may turn brown 
  • Leaves may turn brown and die



If you do not correct high EC levels then your entire plant can die. 


High EC levels can lead to leaf damage, stunted growth, and possible death of your plant. We recommend performing periodic EC checks to ensure the nutrient levels in your plants are within proper levels. 


How to test for EC:

  • The more fertilizer salts that are present in your nutrient solution the higher your EC reading will be.
  • EC can be tested with a meter directly into your reservoir or by performing a runoff test. 





If you are growing in soil it is a good idea to test your soil’s PH and EC to determine whether or not soil amendments should be made.


There are three different methods you can use to test the PH and EC:


The 2:1 Technique: 

This method is quickly and easy!


You Will Need:

  • Distilled water
  • Measuring cup
  • pH and EC meters.




Using two parts of distilled water and 1 part soil sample (taken from various areas in your crop (for accuracy), mix the two parts together.
An example would be 1 cup of distilled water to a 1/2 cup of media.
Give the solution a really good stir before letting it sit for an hour.
After the organic sediment has settled to the bottom of your container, use your meters to test the pH and EC of the water near the surface of your sample solution.
Some meters may require you to filter the solution prior to testing. If you are having trouble getting a reading from your meter, simply filter the solution through a coffee filter and then take your reading.  
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The Pour-Thru Method: 

This is the only method does not require a soil sample!⠀⠀⠀


Irrigate your plants until completely saturated and wait one hour.


You will need a clean receptacle below your pot that allows you measure fluids in mL.


After waiting one hour and using distilled water only, slowly pour the distilled h2o on each of your saturated pots.


Collect the first 50mL of leachate for testing. Distilled water needs to be applied to each pot to yield 50 mL (1.7oz) of leachate.


Using a pH and EC meter, test the leachate as soon as possible, as the pH will naturally rise in a couple of hours.




The Saturated Media Extract Method or SME: 

This method is accurate because it requires representative samples, which results in a better indication of your actual soil conditions.


Media samples are collected in plastic or glass receptacles from various locations within your crop.


After the samples have been collected, slowly add distilled water to your samples to saturate to the point of making a slurry (paste-like consistency).


Let the slurry settle for one hour. After 60 minutes you can then filter the slurry through a coffee filter.


When you’ve completed filtration, test the pH and EC of the resulting liquid using your pH & EC meters.


Each of these methods will require referencing charts that show what the readings of each method indicate in regards to your pH and EC. The data resulting from each method must be analyzed using the tried and true conversions that can be found in the chart below. These conversions are specific to each testing method.





Pour Thru


0 to 0.03

0 to 0.8

0 to 1.0

Very low

0.3 to 0.8

0.8 to 2.0

1.0 to 2.6


0.8 to 1.3

2.0 to 3.5

2.6 to 4.6


1.3 to 1.8

3.5 to 5.0

4.6 to 6.5


1.8 to 2.3

5.0 to 6.0

6.6 to 7.8

Very High





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Any questions? Email us at or send us a message on Instagram @futureharvestdevelopment and we will help you as best we can!

    Published by Future Harvest

    Future Harvest | Grow Better |


  • Dec 07, 2021
  • Category: Articles
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