About      Products      Blog      Gallery      Contact

Home > Blog

Nice and EC does it

Why and how to control the EC of your feed solution

EC (Electrical Conductivity) is a measure of how well a material conducts electricity, in units called Siemens (usually microSiemens (µS) or milliSiemens (mS)). Pure or distilled water is a poor conductor of electricity, but as nutrient salts are added its electrical conductivity increases. It follows that by measuring the EC of a hydroponic feed solution, we get an understanding of the concentration of nutrients that it contains. Ideal EC varies by plant type and stage of development. Young plants and light feeding plants such as lettuce prefer a lower EC, while older plants and heavy feeding plants such as tomato prefer a higher EC. When EC is too low, a low nutrient uptake will result in underfeeding, whereas nutrient levels can become toxic when EC is too high. A feed solution EC of 1.8mS/cm / 1,800µS is generally accepted as a safe and adequate level for many types of mature plants.

How to test EC

It is good practice to check the EC of your feed solution every day, at least until you get a feel for how your system behaves. A test can be performed using an EC meter. Inexpensive 'pen' style meters, suitable for amateur use, are readily available online and are reasonably accurate. Highly accurate and more expensive meters, available from hydroponic retailers, are the preferred choice of professional growers. Meters require regular calibration (i.e. adjusting to match a calibration solution of known EC; also available online) to ensure that readings remain correct. It is best to avoid meters that measure nutrient concentration in PPM (Parts Per Million). Such meters actually measure EC then convert the result to PPM. The conversion factor is, however, inconsistent between manufacturers so the PPM values can be very misleading.

How to adjust EC

Mineral plant nutrients are used to increase the EC of a hydroponic feed solution. EC is decreased by adding water to dilute the solution. It is advisable to take EC measurements intermittently while adding nutrients or water to the feed, until it is mixed to the desired concentration. Then test again after 10-15 minutes to ensure the EC is stable. The strength of plant nutrients varies between manufacturers and the background EC of the feed source water also needs to be considered. The manufacturer's mixing instructions should serve as a guide to how much of their nutrient is required to achieve a target EC. Generally, a feed solution with an EC of 1.0 mS/cm will contain up to 1.0 gram of nutrient salts per 1 litre of water.

How to manage EC

Plants in hydroponic systems are reliant on the grower to provide all the nutrients required for healthy development. It is therefore essential to use a high quality and well-balanced nutrient product, such as Hydrocrop HydroSol. Filtration systems can prevent unwanted salts being introduced into the feed solution through the source water, but most UK tap water is perfectly safe to use. The EC of the feed solution in a recirculating system can be monitored in the supply reservoir. In a media-based system, it is best to check the EC of the leachate (the solution that drains from the grow bed) also. The EC of the leachate is a good indication of the actual EC in the plant root zone. Make adjustments as necessary to keep EC within the optimum range. Be aware that although EC measures nutrient concentration, it does not show exactly which nutrients are in the feed. The supply reservoir in a recirculating system should be periodically emptied and refilled with fresh feed, because the balance of nutrients will progressively deteriorate.

Why EC changes

Feed solution EC will change over time due to the constant difference in uptake rates of water and nutrients by growing plants. Climatic conditions around plants effect this balance, as does plant size and age. In warm and dry conditions plants transpire more and take up more water, while in colder conditions water uptake is reduced. When in perfect balance, EC will remain fairly constant as the growing plants take up proportionally equal amounts of nutrients and water. The strength of the feed solution should be increased if EC consistently falls. If EC consistently rises, the strength of the feed should be reduced or the volume and frequency of feeding increased. Temperature also has an effect on EC readings because for every 1°c temperature rise the conductivity of the feed will increase by approximately 2%.

To ensure effective nutrition for your hydroponic plants, it’s important to control the pH of the feed solution as well as the EC. You can read more about pH management and control in our blog article Perfecting your pH.

Website and content © Hydrocrop 2021