Electrical Conductivity: The Measurement You Can’t Afford to Ignore

If you want your marijuana plants to thrive, the electrical conductivity (EC) and pH level of the water you use are essential factors. These methods of monitoring crops have been good enough for the floriculture industry for a long time.

Finally, commercial marijuana sellers have seen the light, are paying attention to the EC levels of their plants’ substrate, and are reaping the rewards. If you’re growing cannabis indoors, learning about EC can play a major role in decreasing the number of nutrient-related issues your plants experience.

Below, we investigate what EC is, provide data on the optimal range, and offer solutions on what to do if the reading is too high or too low.

What Is EC?

In relation to marijuana growing, electrical conductivity is the electrical charge that moves through the solution you use. When it comes to your plants, it relates specifically to the water they consume. An EC reading is elevated when there is a high salt concentration within a solution.

While water can conduct electricity, its capacity to do so depends on the volume of minerals it contains. If it contains plenty of minerals, it can conduct electricity extremely well. However, distilled water won’t conduct electricity.

When you know the EC of the water you use, you can estimate its mineral content. Through this process, you’ll gain an understanding of whether your plants are benefiting. For instance, tap water contains lots of sodium and lime, which means it has a relatively high EC level.

Recommended EC Levels by Growth Stage

The International System of Units (SI) unit of measurement for conductivity is Siemens (S). When measuring EC in water, you use millisiemens per centimeter (mS/cm).

To get the right EC reading, it’s best to measure the runoff water. This is the excess liquid that passes through your marijuana plant’s root zone and substrate.

It’s also essential to get the parts per million (PPM) reading. This outlines the amount of nutrients within the growing medium. Once you have the EC and PPM readings, you have guidance on how to feed your plants going forward.

Here are the optimal PPM and EC readings for marijuana grown in soil at selected growth stages.

The EC numbers are quite similar if you’re using a hydroponics setup, although you could reduce them by 0.1 or so. Regarding PPM, decrease it by between 50 and 150 until the late flowering stage.

When taking EC measurements, check the nutrient solution AND the runoff. Hopefully, the runoff figure is lower, as it shows that your plants are consuming the nutrients you’re feeding them. If the EC number is low, you must increase the volume of nutrients.

If there isn’t any difference in EC between the nutrient solution and runoff, it’s a sign of nutrient lockout. If the runoff figure is higher, a salt buildup around the roots is likely the culprit.

What To Do if the EC Level Is Outside the Optimal Range

Your marijuana plants are quite sensitive to electrical conductivity in water. The EC reading will be high if you use a lot of commercial fertilizer. If you use water laden with nutrients, you’ll find that it doesn’t filter through the plants’ roots correctly.

Here’s what to do if the EC levels are either too low or too high.

Low EC Reading

Your cannabis plants are forced to absorb more water if the EC reading is lower than ideal. Consequently, they expand in a bid to absorb a greater level of nutrients. On the plus side, dealing with low EC is decidedly easier than when the levels are too high.

Increasing EC is as easy as adding more nutrients to your solution. Incidentally, adding CO2 generators in the grow room means you can raise the EC as high as 3.0! However, this is wholly unnecessary if you’re only growing a few plants at home.

High EC Reading

If the EC figure is too high, your plants will have a major problem absorbing nutrients. This is a sign that the fertilizer is accumulating in the pot at a rate higher than what the plant needs.

In this case, decrease the amount of fertilizer being fed to your plants to reduce the rate of salt accumulation. Alternatively, irrigate the substrate with clear water twice to remove the salts.

Use An EC Water Meter

Investing in an EC meter can make life easier. These electric devices have two parts: an electrode and a sensor. The electrode measures the conductivity in the liquid, so you get the EC reading and temperature. If you have a small grow room, a portable meter will suffice, although continuous meters are also available.

When measuring EC, don’t forget the growing medium! By calculating the EC of the runoff and soil, you get a good idea of how well your plants are absorbing the nutrients.

Please note that while EC tells you a lot about the level of fertilizer salts in a solution, it doesn’t help you determine whether your plants are receiving too much or not enough of a given nutrient. That being said, since NPK are the primary nutrients, an EC reading gives a fairly accurate overview of the relative concentration of these essential nutrients.

Overall, an EC reading that’s on the low side is potentially a sign of nutrient deficiency. By contrast, an elevated EC score suggests that you’re using too much fertilizer or that your plants aren’t absorbing the nutrients properly.

Feed Your Plants More Efficiently By Measuring EC

Hopefully, you now understand how important it is to measure electrical conductivity. Make sure you perform the test on the growing medium and the runoff water to find out whether your plants need more or less nutrients. When you’re armed with this information, you can adjust the feeding schedule appropriately and ensure your plants experience uninterrupted growth.