How Electrical Conductivity Impacts Cannabis Plant Growth

Many of us probably recall sitting in science class listening to a professor talk about cells, atoms, and molecules, including their structural compositions and critical importance to life. Long lectures and endless terms such as electric conductivity, osmosis, and ionic exchanges were memorized and subsequently tested on.

However, most of us probably thought we would never come across those terms again in ‘real world’ experiences, especially when growing marijuana. Welcome to the 2021 real-world science program where those terms and many others are now commonly used in cannabis cultivation.

Think of growing cannabis as one big science lab in the real world. Following procedures and understanding data teach growers how to optimize their growing practices to produce the utmost potential out of a marijuana plant.

While many scientific principles should be applied when growing cannabis, understanding electrical conductivity (EC) is at the top of the list. Growers using hydroponic systems, in particular, will learn valuable insight into how a marijuana plant is growing by monitoring EC readings.

Are you ready for a real-world cannabis science lab? This article takes a look at the science behind electrical conductivity and how it impacts cannabis plant growth.

Understanding Electrical Charges in Nutrient Solutions

Hopefully, some topics from in-school science class, such as atoms, ions, and electrical charges, come to mind as we discuss this principle.

Briefly recapping, atoms have neutrons, positively charged protons, and negatively charged electrons. If an atom has an equal amount of protons and electrons, it is electrically neutral. However, if the number of protons does not equal the number of electrons, the atom has an electrical charge.

These charged atoms or molecules are called ions. Ions bearing a positive charge are cations, while negatively charged ions are known as anions. In simple water molecules, ions dissociate to form either a positively charged hydrogen cation or a negatively charged hydroxide anion.

Nutrient compounds also have charges depending on their molecular structure. For instance, sodium chloride, which is just plain table salt, is the molecular compound NaCl. When table salt combines with simple tap water, the molecule dissociates into the cation Na+ and the anion Cl-.

When nutrients (salts) combine with water, ions hook up with mineral particles dependent upon an element’s charge. Similar to magnets, ions are attracted to opposite electrical charges and repelled by like ones.

A high concentration of ions within a solution leads to a greater flow of electrons. Highly reactive charged ions bounce electrons around in the solution, creating and rearranging bonds dictated by the electrical charges. This motion leads to an electrical current moving through the solvent.

Electrical conductivity measures the potential for the electrical current to transport through the solution. More ions flowing through a solution increases its conductivity. EC is a measurement of the salt concentration produced by the ionic activity in a nutrient formula.

Interpreting EC Readings for Optimal Nutrient Uptake

EC measurements reveal the mineral salt concentration in a substrate. Another way to interpret EC is by looking at it as the nutrient uptake capacity of a marijuana plant’s root system. If EC readings of a fertilizer solution going into a plant are slightly higher than those from the run-off coming out, the plant is doing well. It is taking up all of the fertilizer provided and is not stressed due to undernourishment.

On the other hand, if readings are either very high or substantially lower, there is a definite problem with nutrient uptake in the root zone. Chances are, a grower will encounter high toxicity readings before low ones. This circumstance happens because fertilizer salts tend to accumulate in root zones when the cannabis plant can’t uptake all of the nutrient molecules.

Osmosis tries to regulate nutrient flows in the root system by moving less concentrated solutions to more concentrated ones. Plants absorb water through membranes in their roots. When a nutrient solution is applied to the root zone, it is unable to pass through the membrane initially due to the high salt concentration.

However, the marijuana plant produces sugars inside the root through the photosynthesis process. As the sugar concentration increases, osmotic pressure forces nutrient concentrations on the outside of the membrane to enter the plant. This permeation allows for abundant nutrient uptake.

If the EC of a nutrient solution is too high, the plant’s ability to increase sugar concentration in the roots is compromised. In this instance, osmosis will reverse as the plant sends water outside the root membrane. Nature provides this action to dilute the high salt concentration of the nutrient solution. Reverse osmosis causes dehydration within the plant, showing dry, crispy curled-up leaves.

With low EC readings, the marijuana plant is experiencing nutrient deficiencies and is letting you know it is hungry and needs more food. The leaves will turn a pale green, and the foliage will be wilting and soft. Raise the EC by increasing the amount of nutrients incrementally until readings stabilize to ensure the plant receives adequate nutrition.

What Are Good EC Levels for Cannabis Cultivation?

There are several factors that affect the answer to this question.

First of all, what type of substrate will the cannabis plant be grown in?

Rich, organic soil is a beneficial buffer for many additives. As the microbial colonies within the root zone signal enzymes to help break down complex nutrient formulas, organic soils do not require high EC solutions. Light soils without pre-charged nutrients, on the other hand, will require fertilization throughout the plant’s life cycle.

Hydroponic and soilless growers have a pretty clear picture of how their marijuana plant reacts to a nutrient recipe by monitoring EC values. Comparing electrical conductivity measurements of solutions going into the substrate with readings as the solution exits the plant base provides good data for a grower. Hydro growers can fine-tune nutrient recipes simply by monitoring EC levels.

What life stage is the cannabis plant in?

Young clones or developing seedlings need nutrition as they develop their root systems. Start with low-dose fertilizer formulas with EC ranges between 0.5 – 0.7 during the first weeks and watch how the plant responds. When new fresh growth begins emerging, bump the nutrient levels up a little.

As the cannabis plant starts to fill out during the vegetative stage, the added foliage needs ample NPK. Secondary nutrients such as calcium and magnesium in addition to micronutrients should be included in the recipe, especially when growing hydroponically.

EC readings in veg can range anywhere from 1.0 – 1.5 based on how the plant is performing. Slow and incremental EC upticks in the nutrient solution encourage plant development and prevent salt buildup.

Flipping to a 12-12 light schedule signals the reproductive stage to begin. As the plant develops into the pre-flowering phase, the nutritional requirements change. Bloom formulas reduce nitrate additives while increasing phosphorus and potassium inputs.

EC levels should remain stable at this stage as the plant adjusts to the fertilizer change. Keep flower feeding EC measurements close to the vegetative supplement levels initially to minimize stress. EC measurements can increase steadily up to 2.0 – 2.2 in the flowering stage, depending on how the plant reacts to the formula.

Create Your Own Science Lab

There are charts online that reveal optimal EC levels for different growth stages and substrate recommendations. While these are great reference points, the best way to learn the optimal EC units for your nutrient recipes in your grow set-up is through diligent data recordings.

First-time horticulture growers, and even those with some experience under their belts, will learn more about their growing environment from taking daily room measurements. Simple recordings of temperature and relative humidity levels reveal more than numbers written on a log. These two controls have a lot of influence over cannabis plant development. PH is another high influencer in cannabis cultivation.

Jot down nutrient recipes and record pH levels and EC data from inputs and outputs. As the plant responds to new formulations, note any changes. While it may seem mundane initially, reflecting on data compiled throughout the life span of the tasty bud you are now enjoying will be worth the effort.

While there is much to learn about cultivation practices, the most fundamental criteria for cannabis plant development is proper plant nutrition. Knowing how to feed the plant the best diet based on its’ needs is possible with a better knowledge of the science behind it.

Grow Good Genetics

Growing cannabis is much easier when you know how a particular strain is going to develop. From heavy-feeding, insatiable Indica genetics to tall, vibrant Sativa dominant cultivars, a base knowledge of how a cannabis strain will perform is a huge asset. Stable genetics provide sound growth habits while exhibiting exceptional cannabinoid and terpene profiles.