What is EC?
EC stands for Electrical Conductivity, or the ability of a solution to conduct electricity. Electricity moves efficiently through water with high levels of salt present (high EC), and less efficiently (low EC).

EC indicates how much dissolved salt is in a give sample. That is why EC if also referred to as TDS (Total Dissolved Salts) or Salinity (the amount of salts in a solution). All nutrients are salts, so EC is the same as measuring total nutrients in a solution.

Why measure EC?
Knowing your EC levels will help in plant production and monitoring of inputs. Moisture in soil that has high salt levels will not move into the plants' roots, causing drought symptoms even when there is plenty of water present.

How is EC measured?
EC is measured by an EC meter, which is also known as a solubridge. These meters normally look like pH meters, but instead of the glass bulb electrodes, EC meters have metal prongs or bridges to measure the electrical current that passes between them.

EC is measured in mS/cm (milliSiemens per centimeter). Various EC meters measure in different ranges. Some meters even read low enough levels to measure in µS/cm (microSiemens per centimeter). It takes 1,000 µS/com to equal one mS/cm.

In some instances, you may see EC measured in PPM (parts per million). You can purchase meters that will read EC in PPM or convert and mS/cm reading to PPM. To change mS/cm to PPM for aqueous solutions, multiply the reading by 640. For converting 1:2 ratio soil solutions, multiply by 1,500 to get a reading in PPM.

How do you make EC measurements?
Measuring EC in aqueous solutions if fairly simple. You calibrate your meter, and then submerse the sensor into the liquid. However, there are many methods for measuring the EC of soil. One is the wet paste method, where you add distilled water until the soil glistens and a small amount of water creeps up the side of the container when tilted. Another is a 1:2 method of mixing one part soil with tow parts distilled water, then testing the soil slurry.

For convenience, you may test the same solution you prepared for pH readings in a 1:1 ratio. For quick soil EC measurements, greenhouse growers may test the water that drips out of the bottom of the plant containers.

Contact your local Extension agent or land grant university for more information on how to take soil EC measurements for your plants.

EC in fertigation systems
Fertigation is a system that applies soluble fertilizer to plants through irrigation water. It's common in greenhouse, hydroponic and irrigated high-value crop and ornamental production. Adding fertilizer to irrigation water increase EC since fertilizers are salts.

To use EC to check fertilizer levels, first check the EC reading of your water. Then take an EC reading of precise mixture of your fertilizer and irrigation water in the desired concentration. To check the amount of fertilizer that was added, subtract the reading for your water from the fertilizer that was added.

Now, check your fertigation water at any point along the system. Its EC should match the readings for the mixture. If it doesn't, check injectors, valves and nozzles for blockage or other problems.