When we talk about EC (electro-conductivity) in hydroponic cultivation, we are dealing with the measurement parameter that determines the quantity of mineral salts dissolved in the water. In the case of hydroponic cultivation, the EC tester essentially detects the quantity of fertilizers present in the nutrient solution. Obviously an EC tester does not tell us which nutrients are present, but the total presence of them.

In this regard, it is useless to underline the indispensability of an EC conductivity meter in hydroponic cultivation. To make you understand the importance of this tool, imagine having to feed your child, who at the age of 3 will need to assimilate a certain amount of food, at 5 years another one, at 10 another one and so on. The same thing applies to plants in hydroponic cultivation, which require a certain amount of nutrients for each plant life stage.

EC values ​​that are too high in hydroponic cultivation would strongly compromise the growth of the plants, while values ​​that are too low would slow down their growth.

Ideal EC and ppm parameters for cannabis growing

Why is EC measurement important in hydroponic systems? With particular attention to short-cycle plants, this guide aims to provide practical information for efficient measurement and control of both Electrical Conductivity and PPM.

PPM is a mesurement parameter that mesure how many nutrients can be found into the cultivation substrate.

A high EC value corresponds to a high density and hardness of the nutrient solution, and since plants cannot absorb nutrients beyond a given density depending on the variety and age of life, and considering that in hydroponic cultivation there is no growing substrate that can act as a buffer (as in cultivation in soil substrates), both the EC and PPM parameters are fundamental for the growth and development of our plants.

To give an example: to understand if we use too many fertilizers in hydroponics or too little, just check the EC value of the water found in the tank. The base of our irrigation liquid is fundamental for electrical conductivity, in fact we will have a different EC degree if we use tap, mineral, demineralised or distilled water, for example.

It is good to keep in mind that any nutrient added to our water will increase the EC level. Each product on the market for cultivation fertilizer has its own electrical conductivity, and will change the EC of our irrigation liquid in a different way.

Therefore it is important to always follow the dosages recommended on the label and monitor the EC of the irrigation liquid every time a new substance is added. Tap water usually has a high EC, which can vary from 0.4-0.5 ms/cm up to exaggerated values ​​such as 0.7-0.8 ms/cm. In this regard it is always good to make sure of the measurement of the EC of water with both active and passive hydroponic systems.

ppm and ec values in hydroponics growing

What is the average EC value to be respected in hydroponics during the various phases of plant growth?
In reality, it is difficult to give a single value as each plant species requires different EC parameters during the various phases of plant growth, much depends on the hardness of the water we use for irrigation and the nutrients we add. However, based on experience, we can recommend some indicative values ​​regarding hemp plants:

  • The EC value increases depending on the growth period of the plant.
  • In the vegetative phase 0.8-1.2 ms/cm.
  • In the flowering phase 1.2-1.8 ms/cm.
  • For example, short-cycle plants require a low EC value in the early stages of life to be able to absorb nutrients, which is usually around 0.5-0.6 ms/cm for both new born and cuttings. Subsequently the plants are ready to tolerate higher EC values, from 1.0 ms/cm in the pre-flowering phase up to 1.5-1.8 ms/cm during flowering, but always lower than 2.0 ms/ cm.

Mineral waters have specific electrical conductivity values ​​written on the label, light waters have optimal hardness values ​​for our purposes, in fact if we had a low EC value at the start, we could add the necessary quantities without giving hardness to the irrigation solution, with disastrous consequences for our plants.

Demineralised water can be purchased in supermarkets, usually the kind used for irons, dehumidifiers etc. It can also be made at home with a reverse osmosis system. Demineralised water can be used to reduce a high EC value in the irrigation liquid or as a base if, for example, you want to use balanced powdered mineral compounds on the market for hydroponic crops, so that from an almost neutral base you can build an ideal liquid for watering plants.

Exact monitoring of the EC values ​​of our irrigation solution is the key to an excellent result in hydroponic cultivation; underestimating the consequences of a high or low electro-conductivity value of the water can lead to almost disappointing results and consequent abandonment of the hydroponic cultivation technique.

If we take into consideration a medium-small hydroponic system with a 30-40 liter tank, ideal for short-cycle home cultivation of plants, we will have to calibrate the irrigation liquid for electrical conductivity only four times: at the beginning, in the vegetative, flowering and finally the final rinse. Plants extract fertilizers and water from the nutrient solution at the same time, but not always to the same extent. In a hot climate plants tend to drink more, and together with the high evaporation rate this makes nutrient concentrations too high.

How to control and measuring the electro conductivity in cannabis growing

To keep the EC in hydroponics stable and under control and therefore the balance of the solution, it is important to equip yourself with appropriate tools. As mentioned in the first paragraph, this value is the only way we have to precisely check how many nutrients still persist in the water. Too high a presence of these nutrients can damage our plants, while a very low presence would lead to deficiencies and poor development of the plant.

To measure EC, an instrument is used, called an EC tester which, as mentioned, indicates the quantities of salts dissolved in the water. There are different models of instruments for measuring EC: portable, fixed with probes and of various price ranges. However, these instruments require constant ordinary maintenance if you want to make them work correctly, but above all to make them last longer.

The instrument must first be calibrated, with the aid of the appropriate EC calibration liquid, a basic expedient for the precision of the measurements. In practice you need to immerse the electrode in a calibrated EC solution and set the instrument, as illustrated in the instructions. Once the calibration has been carried out, the electrode must be cleaned with distilled water every time it is used.

Nonetheless, it would be advisable to soak it in another solution called storage solution, which significantly extends its life. In conclusion, EC measurement in hydroponic cultivation must be carried out very carefully in systems that recirculate water, depending on the plant species being cultivated if you want to be successful in the hydroponic cultivation technique. 

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