The ideal concentration of mineral salts in a nutrient solution is necessary for healthy plant development. It belongs among the most vital quantities a grower needs to watch during the growth cycle. To determine the concentration, growers rely on EC (electrical conductivity). How can we measure it, and what EC levels are best for a juicy harvest?
Electrical conductivity is the easiest way to measure how many nutrients there are in the irrigation or nutrient solution. In the case of hydroponics or aeroponics, the concentration of mineral salts in fertilisers and water from the tap or well is crucial.
Electrical conductivity is the ability of a substance to conduct an electric current. Salts and other chemicals can break into negatively and positively charged ions when they dissolve in water. These ions can conduct electricity, so the conductivity of water depends on how much total dissolved solids (TDS) it has. For example, distilled water is almost an insulator, while saltwater is a very efficient electric conductor. Some growers also use TDS to measure the amount of nutrients in a nutrient solution. Electrical conductivity is expressed in mS (micro Siemens).
Most often, growers use tap water. EC of the tap water differs from place to place. For example, here in the Czech Republic, the EC ranges from 0.3 to 0.7, which is not commonplace, and growers are rightfully glad for it. Some places can have tap water with EC from 1-2. The lower the EC levels, the better because water is not the primary source of nutrition for plants – fertilisers are.
You should watch the EC level carefully when making a nutrient solution. Why? Let’s use an example. If we know upfront that the nutrient solution should have an EC of 1,9 and that the water we use for it has (by itself) 0,6 EC, we can only add 1,3 EC of fertiliser instead of the possible 1.9. Too many dissolved solids in a nutrient solution or irrigation water can burn the plants, no matter their source. What’s worse, the minerals and salts which increase its EC value are usually unusable by plants, so it’s best to use water with low EC.
TIP: Increase the fertiliser dose gradually. Experienced growers avoid using too much or too little fertiliser by increasing the EC in increments of 0,1-0,3. The plants are much more able to absorb the nutrients in the fertiliser than they would if the concentration increased abruptly.
The recommended EC value is not constant and differs for individual growth phases. It’s necessary to point out that different plants have different needs, but in general, the recommended EC value is as follows:
- Young plants: 0,6-1,2 mS
- Older and larger plants: 1,2-2,5 mS
We use EC meters to measure and then maintain the EC level. Unlike pH meters, they usually don’t need storage solutions, and their probe is made of metal. In terms of calibration, there are digitally and manually calibrated devices. The overwhelming majority of growers use digital EC meters, which are more appropriate even for beginners because they usually automatically compensate for the temperature of the solution, and there’s no risk of damaging the device by calibrating it wrong.
Calibrating solutions are liquids with a known EC value used to reset the device and make sure it measures precisely. The solutions are usually available in 1,413 or 2,78 mS options.
TIP: You can also measure the EC level of the potting soil when flushing to know just how effective the process was.
Finally, we would like to point out that tables and recommended values are one thing but observing the plants is just as important. You can tell by looking at the leaves and stems if the plants need less or more fertilisers, and with growing experience, you’ll be able to tell if you’re causing fertiliser burn or if they suffer from a deficiency.
We hope the plants flourish under your attentive care and that our advice (and the products from our website) helps you reach that joy of a job well done. If you’d like to get more information on EC meters, calibration, fertilisers or just about anything concerning plant cultivation, contact us at info@higarden.eu.
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