Calculate and control your EC level
The electrical conductivity (EC) of your nutrient solution is a critical parameter in greenhouse cultivation. EC directly influences water uptake, plant growth, and ultimately, crop performance. Alessandro Montanarella, consultant at Saint-Gobain Cultilene, shares how you can calculate and control your EC and better understand its impact on your crop.
What is EC and why does it matter?
EC measures the amount of dissolved nutrients in water and indicates how easily plants can absorb the solution. Think of it as drinking through a straw: low EC feels like drinking through a wide straw - little effort is needed to take in enough water. High EC, on the other hand, feels like drinking through a narrow, long straw - even with great effort, only a small amount is absorbed.
Technically speaking, high EC increases osmotic pressure, meaning plants must work harder to take up water. This can be beneficial for steering generative growth. But if EC levels are too high, it restricts overall plant growth, potentially negatively affecting yield.
Calculate the right EC
How do you calculate the right EC level? While experience or intuition can help, it is better to calculate the exact value using the following formula: EC = total sum of milli-equivalents / 20.
To calculate the optimal EC for your solution, use the following steps:
- Convert nutrient concentrations to milli-equivalents (mEq): each nutrient has an equivalent weight based on its chemical composition. For instance (see table below)
- Add up all the milli-equivalents: include major nutrients like potassium, calcium, and sulphate. Micronutrients like iron are typically excluded due to their minimal quantities. In this example, the total of the milli-equivalents is 56.23.
- Divide the total by 20: this gives you the estimated EC of your nutrient solution. For instance: EC = 56.23 / 20 = 2.81.
Set your target EC-levels
Now that you know how to calculate your ideal EC, it’s time to set your target EC-levels. How do you determine these?
Start by considering the different growth stages of your crop. Define these stages clearly and establish boundaries for transitioning to the next phase. Also, record your goals for each stage: are you aiming for vegetative or generative growth, or do the plants perhaps need a recovery period? The more specific you are about your objectives, the better.
Next, identify the target figures you are aiming for. This could be a single figure, such as the dryback at the start of the crop, or the limits you want to maintain. Use historical data and your own experience to create a growth plan tailored to your greenhouse conditions, water type, crop, and other factors that might influence growth.
Make sure your growth plan is flexible, so you can respond to unexpected circumstances. For example:
- During long periods of low light, a higher EC can help steer the plant toward generative growth.
- During high light and high transpiration conditions, a lower EC helps facilitate water uptake for optimal transpiration.
To illustrate this, below you’ll find an example of season dynamics for short day planting tomatoes.
Making adjustments
It’s common for EC levels to deviate from the set goals when going through different phases of growth, changes in light or temperature and because of natural differences in the nutrient solution or water. When this happens, adjustments are needed. Make these changes gradually to avoid stressing the plants.
To lower EC, you can increase the frequency of water doses, increase the drain percentage or decrease the concentration of nutrients in your solution. Stay within the recommended margins to avoid mistakes. To raise EC, you can reduce the amount of drain or increase the concentration of nutrients in your solution.
Also, consider the daily dynamics of your irrigation schedule. Distribute water doses according to the daily dynamics to ensure even water and nutrient distribution. This minimises EC variations within and between slabs.
Optimizing irrigation strategy
Effective EC management supports healthy plants, higher yields, and better fruit quality. Beyond setting goals and monitoring, understanding the relationship between drip-, slab-, and drain-EC provides a powerful tool for optimizing your irrigation strategy. For example:
- Drip EC: this represents the nutrient solution you provide to the plant. Adjustments here directly affect slab EC.
- Slab EC: this is the EC within the substrate, reflecting the immediate environment of the roots. Consistency in slab EC ensures optimal nutrient availability.
- Drain EC: this reflects the excess solution leaving the substrate. Monitoring drain EC helps identify over- or under-fertilization and adjust the balance accordingly.
- Drain/Drip EC: this can be an indication for over- or under watering. Adjust the balance accordingly.
By analysing these values together, you can detect imbalances and fine-tune your approach. For instance, a significant gap between slab and drain EC might indicate uneven nutrient distribution or water uptake inefficiencies. Regular adjustments, informed by these insights, enhance nutrient efficiency, reduce waste, and improve overall plant performance.
Would you like to learn more about nutrient management and Cultilene’s substrate solutions?
Alessandro Montanarella
Application Specialist
[email protected]
+39 (0)3 48 09 17 062
The information provided by Saint-Gobain Cultilene has been compiled with great care and is intended solely as a guideline for the user. Saint-Gobain Cultilene therefore cannot guarantee any errors and no rights may be derived from the information or advice provided. The user himself is responsible for checking the accuracy and suitability of the information and advice for application. No commercial use may be made of the information and advice provided by Saint-Gobain Cultilene, in whole or in part, without the written consent of Saint-Gobain Cultilene.
