Electro conductivity and cannabis cultivation

What is EC or electro conductivity?

In this post we will focus on explaining the concept of EC or electro conductivity for cannabis cultivation and we will explain the importance of EC to obtain good results in our home grow.

Reverse osmosis filter
Reverse osmosis filter

The EC is the capacity of a liquid to transport electricity. Water, the medium by which plants feed, contains dissolved minerals called aqueous solutions. These aqueous solutions may have more or less mineral elements (salts) that will directly influence EC levels.

Not all water is conductive, and by itself, it is not. Distilled water has an EC of zero which means that it will not conduct electricity. To make this water conductive, we must add mineral salts and make a solution. We will provide these salts in the form of organic or mineral fertilisers.

There are osmosis filters that leave the water clean of impurities so that water with zero EC is obtained. These devices are used by those growers who have water with a high initial EC, of ​​more than 0.6 points and use a mixture of both to obtain a starting EC of 0.4 points. It is also possible to adapt our osmosis water with calcium and magnesium micronutrients with a dosage of one part of magnesium for two of calcium from EC 0.0 to 0.4. From this point, we will add the fertilisers until the desired EC is achieved according to the indicated week.

EC meters

To know the level of EC that we are using to water our plants, it's best to use electronic meters. These are electrical devices made up of a probe and an electrode that are responsible for calculating the conductivity of a liquid. There are those that take continuous measurements and others that are discontinuous and used when you want to make checks.

  • Continuous meters are those that constantly measure the EC level. They are made up of a mobile probe that we can leave in the tank, allowing us to monitor the nutrition that we are providing to our plants at all times. This mobile probe is connected through a cable to the console where the transferred data can be read.
  • Portable or compact electronic meters are those whose probe is attached to the console and are indivisible. The meters make measurements in particles per million (PPM) or Milisiemens (Ms) and the most common are in Ms.

Some devices measure EC, pH and water temperature
Some devices measure EC, pH and water temperature

Depending on the type of substrate used, an EC meter will become essential. In those inert substrates, such as coco coir, clay pebbles, rock wool, etc., the dosage of food must be correct according to the state of life of the plant, since the substrate will not contain any elements for the plants to feed on, meaning that we will have to add nutrients in each irrigation.

When we cultivate in soil enriched with humus, guano, etc., it will already contain nutrients and consequently an adequate EC so that the plant can feed without fear of having deficiencies due to lack of fertiliser.

On the other hand, if we cultivate with low-fertility soil (such as a light mix), it will be necessary to add fertiliser from the beginning of the crop to ensure the correct development of the plants.

How to know the EC level of the substrate

To know if the substrate of the cannabis plants is saturated with salts, which can cause a nutrient lockout or over-fertilization, all we have to do is know the EC level of the residual or drainage water of the pot after carrying out irrigation.

The first thing we will do after verifying that the input EC is different from the output EC, the output EC being much greater than the input EC, will be irrigating with water-only, using triple the volume of the pot's capacity, without fertilizer, with a PH adjusted to suit the life stage of the plant and the substrate used. Later we collect the excess water from the irrigation and with the meter, we observe the concentration of EC that it gives us. If we observe that the EC of the drainage is within acceptable parameters, we will have carried out a good root flush.

For coconut and hydroponic crops, we will carry out a root flush with triple the amount of pH-stabilised water without any fertilizer when the EC of drainage run-off exceeds 2.5 points. In this way, what we will achieve will be to greatly reduce the amount of EC in the substrate, favouring better conditions for the plants so that they can recover from over-fertilisation in just a few days.

When growing in soil, root flushing will be carried out when the EC exceeds 2.3-2.4 points and we will leave the substrate clean to irrigate again with the appropriate amount of fertiliser once it has dried. In soil crops, these measuring devices need not be used, but we must bear in mind that we will be controlling the plants in a less precise way than if we do it using an EC meter.

Weekly EC levels
Weekly EC levels

Reverse osmosis process in over-fertilisation

We have explained how to prevent the plants from overfeeding with the help of some meters to mark us some action ranges and thus avoid having problems derived from the subscriber. If these problems are not resolved, a process called reverse osmosis occurs.

Cannabis plants, like all plants, have roots. The roots are responsible for capturing the mineral salts and transforming them into assimilable food in order to grow. These roots are composed in part of water and dissolved salts that vary according to the stage of life in which they are found. In other words, they have variable EC levels from the moment they germinate until they are harvested.

These roots feed correctly when the EC level of the substrate is lower than the EC level of the roots. The problem occurs when the EC level of the root is lower than that of the substrate since the plant will try to stabilise the substrate by evacuating water via the roots to dilute the EC of the substrate and make it more similar to that contained in its roots. The consequence of this process is dehydration and later death.

It is recommended to cultivate using EC meters because we can provide and control the necessary nutrition according to the life stage of the plant and thus facilitate the growth and flowering of cannabis plants.

It should be noted that each plant, depending on whether it is indica or sativa, supports one or another different EC levels. Indica cannabis plants typically have caps of EC 2.2 for hydroponic cultivation and EC 1.8-2.0 for soil cultivation. For sativa varieties, as their feeding is slower and more progressive, in hydroponics the limits will be 1.8 and in soil, the EC will be 1.6-1.7 points. Although it should be noted that these levels can be modified according to the needs of the plant, variety, number of irrigations, amount of irrigation provided, etc.

Salt-free substrate just a week away from harvest
Salt-free substrate just a week away from harvest

Water temperature

There are many factors that influence the actual EC that the plant supports or can absorb. It should be noted that oxygen is one of the elements that facilitate the absorption of food to a greater or lesser extent depending on the temperature of an aqueous solution used to feed cannabis plants.

The temperature of our nutrient solution dictates how well the plant will be able to feed. In a solution with a temperature of 18-20ºC, the cannabis plant can have 100% of the food available. On the contrary, with a temperature above 30ºC, the oxygenation will be much lower and the capacity of the plant to feed itself will be greatly reduced due to the lack of oxygen in the solution, potentially leading to root rot and consequently death by suffocation. So it is important to take these factors into account to have a fully optimised crop.

Oxygen concentration according to water temperature
Oxygen concentration according to water temperature

The pH is also a factor to take into account since, like oxygen, it will be necessary to have it controlled under certain parameters to facilitate the feeding of the cannabis plants, which we will explain in future posts.

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