13 Things You Should Know about EC and pH

13 Things You Should Know about EC and pH

Measuring pH and EC may seem complicated at first sight. Well, it is not so complicated, and the data are extremely useful to any grower in certain cases. Especially when growing indoors and in hydroponic systems. Here we bring you thirteen answers to the most interesting questions about EC and pH.

What does pH actually mean?

We use the term pH scale (from the Latin potentia hydrogenni) to express the acidity of a solution – from acidic to alkaline. The scale ranges from 0 to 14, with a pH value of 7 being considered neutral. Growers need to take into account that the pH of the surrounding environment affects the roots’ ability to absorb nutrients.

What is the ideal pH of the substrate or nutrient solution?

The ideal pH range when growing in soil is 6.0–6.5. When using hydroponic systems and growing in nutrient solutions, it is recommended to keep the pH between 5.5–6.1.

How to measure pH?

For occasional measurements in soil and solid substrates, a simple pH test kit with litmus papers will suffice. However, in case you are growing hydroponically (i.e. in nutrient solution, not soil) or need to measure precisely, then digital pH pens are a much better choice.

How often to measure pH?

The frequency and method of checking pH will vary depending on your chosen growing technique. The soil substrate automatically regulates the pH to a certain extent and you can get by with an indicative measurement, repeated several times during the growing cycle or in the event of unexpected nutritional problems. In the tanks of hydroponic systems, the pH of the nutrient solution needs to be monitored continuously, for example with a special probe.

How to measure the pH of pot-grown plants correctly?

First, water the plants with a regular amount of nutrient solution and, after about 30 minutes, pour about 1 to 2 litres of clean, fertiliser-free water through the growing container. At least one decilitre of water should come out from the holes at the bottom of the pot. You will take the reading from this water. To prevent the pH probe from drying out, store it in a maintenance solution between measurements.

How do I adjust the pH of soil or nutrient solution?

To adjust the pH, we need to use special solutions that require just a few drops per litre of water. You can choose between formulations for the growing or flowering stage.

What does EC mean?

EC stands for the electrical conductivity of given material, in our case the soil or nutrient solution in the container. The vast majority of modern devices show EC values in mS (millisiemens), but sometimes we can come across the more obsolete ppm (parts per million). By measuring the EC, growers obtain an accurate indication of how much mineral salts (nutrients) are dissolved in the nutrient solution or in the substrate. This is especially important when using highly effective mineral fertilisers because certain levels of mineral salts are toxic to plants. The higher the EC value, the more dissolved minerals are present in the measured solution.

What is the ideal EC value?

The ideal EC value (the amount of dissolved minerals) varies according to the type of plant and the growth stage it finds itself in. Young seedlings or fertiliser-sensitive varieties require soil or nutrient solution with a low EC of around 1.0 mS. However, in case of some highly productive varieties, the EC levels can be increased up to 2.5 mS as harvest time approaches.

What does the EC have to do with water hardness?

The EC of distilled water or rainwater is 0 mS because it contains zero dissolved minerals. In tap water, one can usually find some calcium, magnesium and other minerals that increase its conductivity (EC). In the Czech Republic, for example, the EC of tap water ranges approximately from 0.3 to 1.0 mS. If the EC of your tap water is too high (meaning the water is too hard), think about installing an osmotic filter.

How often should I measure the EC?

If you use water-soluble mineral fertilisers, it is important to maintain correct EC every time you irrigate your plants. When growing in soil, we recommend measuring EC at least once a week. In hydroponic systems, it is important to keep checking the EC of the nutrient solution continuously in order to find out early enough whether additional nutrients need to be added to the tank. EC monitoring probes with automatic temperature compensation come in handy in hydroponic containers.

What to measure the EC with?

We measure EC with special EC measuring pens equipped with mechanical or digital calibration. Do not store EC meters in solution, but always rinse the probe immediately after use and let it dry. Calibration solutions are used for regularly repeated calibrations.

How to correctly measure the EC of pot-grown plants?

First, water the plants with a regular amount of nutrient solution and, after about 30 minutes, pour about 1 to 2 litres of clean, fertiliser-free water through the growing container. At least one decilitre of water should come out from the holes at the bottom of the pot to take the reading.

How to adjust the EC of the substrate or nutrient solution?

When the EC is too low and you need to increase it, simply add more nutrients. To reduce EC levels, simply dilute mineral salts in more water. This can be done easily when growing in hydroponic system. In case of overfertilized substrate in the pot, you just pour a few litres of water without fertilizers to wash out some of the mineral salts. You can also use a flushing solution to help dissolve and get rid of the excess minerals.

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