Understanding Electrical Conductivity (EC) and Osmosis

This article discusses nutrient solution strength and the impact of Electrical Conductivity (EC) on Water Absorption through osmosis in cannabis plants.

Maintaining a consistent electrical conductivity (EC), which is a measure of the nutrient solution strength, is crucial. It supports ideal water absorption in plants through osmosis. Fluctuations or excessively high EC levels can have adverse consequences on plants. Conversely, keeping EC levels steady promotes their health and growth. Developing a solid understanding of the core principles behind EC and osmosis empowers you to effectively manage your cultivation activities. This article covers all the essential information needed to gain an understanding of osmosis, EC, and parts per million (PPM).

Understanding Osmosis: How Plants Get Water

Plants utilize osmosis as a method for absorbing water through their root membranes. Osmotic pressure propels the movement of water, and this process is, in part, regulated by the plant itself. Osmosis consistently operates by attracting water from a less concentrated solution towards a more concentrated one. Nutrient solution resides on one side of the root membrane. The water within the root is located on the opposite side. As plants produce sugars within their roots, the solution within the root becomes more concentrated. This facilitates the movement of water from the nutrient solution.

The fertilizers employed in cultivation encompass various forms of salts. An excess of salt content in the water can impede the plant’s ability to draw water from the nutrient solution. As the salinity of the nutrient solution increases, the plant faces difficulties in accessing water. In extreme cases, osmosis can even pull water out of the plant.

Electrical Conductivity (EC) plays a pivotal role as it measures the salinity of the water. Proficiently managing EC is essential for promoting robust and healthy plant growth. Failing to control EC can result in hampered plant development and severe dehydration issues.

What is Electrical Conductivity (EC)?

Electrical Conductivity (EC) refers to the capacity of a solution, to conduct an electric current. In plant cultivation, EC serves as a gauge for quantifying the concentration of dissolved salts or ions within the nutrient solution.

Water that has undergone filtration through Reverse Osmosis (RO) or distillation possesses an EC of 0. EC is typically quantified in units of millisiemens per centimeter (mS/cm) or microsiemens per centimeter (μS/cm), with one millisiemen equaling 1000 microsiemens. For enhanced precision, we include microsiemens when taking measurements with our meter.

When water contains dissolved salts, such as minerals and nutrients, these substances disintegrate into electrically charged particles known as ions. These ions encompass positively charged cations (like potassium and calcium) and negatively charged anions (such as nitrate and phosphate), enabling the water to conduct electricity. The concentration of dissolved salts directly correlates with the electrical conductivity of the solution – the higher the salt concentration, the greater the EC reading.

EC measurement is invaluable for growers as it allows them to assess the salinity level of their water or nutrient solution. This knowledge is pivotal for monitoring and adjusting nutrient concentrations to maintain optimal plant health and growth.

Ensuring an appropriate and balanced EC level is vital because excessive salinity can hinder the plant’s ability to absorb water and nutrients, potentially leading to growth issues or plant stress. By vigilantly observing and regulating EC levels, cultivators can establish an ideal growth environment while averting potential problems stemming from nutrient imbalances or salt accumulation.

The Relationship between EC and PPM:

While many growers may be more familiar with using parts per million (PPM), it’s essential to recognize that PPM essentially derives from measurements of electrical conductivity (EC). Both EC and PPM convey the same information but employ distinct numerical scales for representation. It’s worth noting that various conversion formulas are available for translating EC readings into PPM values.

The most common conversion method employed by most meters is the PPM500, where an EC reading of 1000 corresponds to a PPM value of 500. U.S. nutrient companies, including General Hydroponics, frequently use this particular conversion method. If your nutrient supplier provides PPM measurements without accompanying EC values, it’s advisable to assume that the conversion used is PPM500.

Grasping the connection between EC and PPM empowers growers to accurately decipher and compare measurements, ensuring precise management of nutrient concentrations to promote optimal plant growth.

It is better to simply follow EC

Using a Consistent Unit or Measure like EC is Preferable

Unfortunately, the PPM500 conversion factor isn’t the exclusive method for converting EC measurements. Some meters employ the PPM700 conversion, where an EC reading of 1000 corresponds to a PPM value of 700 instead. However, EC measurements themselves remain uniform, whether expressed in millisiemens or microsiemens per centimeter, as previously explained. In contrast to PPM readings, EC readings offer direct comparability across various measurements. Hence, experts recommend relying on EC rather than PPM as it simplifies measurements.

Meters typically provide the convenience and flexibility of offering both EC and PPM readings. While having access to both measurements is ideal, if your meter solely displays PPM, it isn’t a major concern. However, it becomes vital to determine the specific conversion factor used by your meter to ensure accurate comprehension and interpretation of the measurements.

Prioritizing EC measurements enables growers to monitor and adjust nutrient concentrations with precision. By giving precedence to EC, growers can efficiently regulate and optimize nutrient levels, ultimately enhancing the well-being and growth of their plants.

EC – PPM Conversion Table:

EC Microsiemens*	500	750	1000	1250	1500	1750
EC Millisiemens	0.5	0.75	1.0	1.25	1.5	1.75
PPM 500	250	375	500	625	750	875
PPM 700	350	525	700	875	1050	1225

*420GrowHelp.com uses EC Microsiemens to discuss EC/PPM measurements across its platform.

What Happens to the Water and the Salt?

When you introduce a nutrient solution into the coco, you’re essentially introducing both water and salts. To understand how electrical conductivity (EC) fluctuates during feedings, it’s crucial to contemplate the fate of each component. Keep in mind that plants don’t uptake nutrient solution as if they were drinking through a straw or absorbing it like a sponge. Under typical circumstances, the plant independently absorbs water and salts (fertilizers). The plant typically draws water up approximately four times faster than it assimilates salts. Consequently, the EC of the nutrient solution within the growing medium will increase between feedings.

What Happens to the Water?

Plant Uptake: Plants absorb water through osmosis, which leads to the accumulation of salts in the nutrient solution within the coco. While plants also take in nutrients, they extract water at a faster rate than salts. The process of transpiration results in the loss of the majority of the absorbed water. This leads to an increase in the electrical conductivity (EC) of the nutrient solution within the coco.

Evaporation: Water within the coco pot undergoes continuous evaporation between fertigation events. This evaporation causes an elevation in the EC of the remaining nutrient solution. Evaporation contributes to an increase in the EC of the nutrient solution within the coco.

Transpiration and evaporation cause the EC in the coco to be at its lowest immediately after fertigation, while the “Peak EC” occurs just before the subsequent fertigation. Fertigation events themselves help lower the EC in the coco, even though it may seem counterintuitive to reduce salt levels by adding nutrient solution. This reduction occurs through run-off.

Run-off: When fresh nutrient solution is introduced into the coco, it displaces the old nutrient solution that was previously held in the coco. The run-off water is not the same as the water added from the top; it has a higher EC due to the effects of transpiration and evaporation. Run-off carries salts out of the coco, and with each fertigation, the nutrient solution in the coco approaches the inflow EC. Run-off effectively lowers the EC by flushing out excess salts.

To effectively manage EC and achieve optimal results in coco cultivation, regular fertigation with adequate run-off is crucial. This process ensures proper water absorption, regulates salt levels, and fosters robust plant growth.

The Consequences of Inaccurate EC on Cannabis Growth

Consequences of High (EC)

Cannabis plants depend on osmosis to uptake water through their root membranes. Naturally, water flows from areas of lower solute concentration to higher concentration levels. To facilitate water absorption, the concentration of sugars within the roots must surpass the concentration of salts in the nutrient solution. Plants have the capability to adapt to this osmotic gradient by producing sugars in their roots, thereby increasing the concentration and encouraging water intake. However, when the nutrient solution has a high EC, it can overwhelm the plant’s capacity to elevate the sugar concentration in its roots.

The Occurrence of “Nute Burn”: When the EC of the nutrient solution surpasses the plant’s tolerance level, it struggles to access water. In severe cases of high EC, osmosis can even reverse, causing water to be drawn out of the plant. This struggle for water and the phenomenon of “reverse osmosis” lead to symptoms commonly referred to as “nute burn” or “fertilizer burn.” These symptoms include wilting, scorched tips, parched leaves, leaf curling, reduced growth, and, ultimately, plant deterioration.

Even minor indications of nute burn signal that the plant is grappling with drawing water against a high EC. Instead of promoting growth by providing adequate nutrients, high EC levels impede growth by depriving the plant of water. It is crucial to promptly address “burn” symptoms. For guidance on managing run-off EC, please refer to our tutorial, “Managing EC with Run-off”.

Consequences of Low EC

When the EC of the nutrient solution is too low, plants tend to absorb excessive amounts of water while generating fewer sugars. This happens because the concentration of sugars within their roots directly responds to the EC of the nutrient solution. In the case of a low EC, plants may initially intake an excess of water as the concentration of sugars in their roots surpasses the concentration of salts in the nutrient solution. However, it’s crucial to understand that this increased water intake doesn’t translate into improved nutrient absorption. While water is absorbed through osmosis, nutrients are taken in through distinct diffusion and transport processes.

A low EC presents the risk of under-fertilization since there is inherently a lower quantity of fertilizer in the water. However, under-fertilization isn’t the sole concern. When the EC is too low, plants produce reduced amounts of essential components, including sugars and other beneficial substances. These components play a vital role in facilitating water absorption through osmosis. Inadequate EC levels lead to diminished production of these valuable substances, potentially hampering the plant’s ability to efficiently draw water into its system.

Maintaining an appropriate EC level is paramount to ensure optimal plant growth and overall health. By providing the necessary nutrients and sustaining a balanced EC, growers can support the production of essential compounds and facilitate successful water uptake through osmosis.

The Impact of Fluctuating EC on Cannabis Plants

When EC Fluctuates

Constant fluctuations in EC place an ongoing burden on plants. To absorb water through osmosis, plants must regulate the concentration of sugars within their roots. When the EC of the nutrient solution is lower than expected, plants absorb excess water, requiring a reduction in the sugar concentration in their roots. Conversely, when the EC of the nutrient solution is higher than anticipated, plants struggle to absorb enough water and must divert their energy toward producing sugars to elevate the concentration in their roots. Even at relatively low EC levels, sudden increases can lead to symptoms of nutrient burn because the roots are already adapted to even lower concentrations.

The common practice of intermittent flushing in coco, which involves alternating between watering with nutrient solution and using “plain,” pH-adjusted, or CalMag water, should be avoided. This practice results in unstable EC levels in the root zone, compelling plants to constantly adapt and readjust. To maintain the well-being of plants, it’s crucial to provide a nutrient solution with a consistent EC during each fertigation event. By ensuring a stable and suitable EC, growers can establish an ideal growth environment, enabling plants to thrive and grow effectively.

Gradual EC Adjustments

Careful Inflow EC Adjustments: A Necessity at Times!

There are situations when adjustments to the inflow EC are necessary, particularly when transitioning through various stages of the plant’s life cycle as indicated by feeding charts. For example, when shifting from the seedling stage to early vegetative nutrients, it’s advisable to incrementally raise the inflow EC. It’s recommended to make gradual alterations, not exceeding 100 points per fertigation and a maximum of 200 points per day.

Taking a cautious approach to EC adjustments enables plants to adapt and accommodate the shifting nutrient concentrations without overwhelming their system. By implementing gradual changes within these suggested limits, growers can ensure a smoother transition and minimize potential stress on the plants during critical growth phases.

Use this Knowledge in Your Grow

To effectively manage strength of nutrient solution (EC) in your cultivation endeavors, we encourage you to explore our comprehensive tutorials. These resources provide valuable insights and practical guidance on how to monitor, adjust, and optimize EC levels for your plants. By applying the knowledge gained from these tutorials, you can enhance the health, vigor, and overall success of your grow. Be sure to read our tutorials, “Setting EC Targets”, “How to Mix Nutrient Solutions” and “Managing EC Using Run-off”.

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Understanding Electrical Conductivity (EC) and Osmosis