EC (Electrical Conductivity) and TDS (Total Dissolved Solids) Meters

EC and TDS meters both measure the amount of dissolved ions in a liquid.  Whereas EC meters measure in Microsiemans per centimeter (µS) a TDS meter measures in Parts Per Million (PPM). However they both measure the same thing.

Knowing the conductivity of your soil is a useful  and simple precision agriculture technique for helping to with your fertilizer decisions.

Conductivity meters measure the number of ions that are mobile within a liquid and is considered the most accurate way of determining the salinity and fertility level of your soil because plants take in nutrients in ion form which means that they carry a current. For examle nitrogen ions, phosphorus ions and potassium ions will all add to the conductivity level of your soil if they are present and available.

EC measurements below 100µS for example may indicate not enough nutrients for the plants whereas numbers greater than 1000µS may indicate that there is pollution entering your soils and high salts accumulating that can cause plant rootlets to burn and microbes to die.

EC meters can be used for a other  purposes too:

• To determine the quality of water, high quality distilled drinking water will ideally have <4 µS, T
• The concentration of liquid fertilizers.
• To test the quality and maturity of compost.
• To measure the ions in plant leaves.

Because EC readings are dependant on temperature, it is best to choose a meter with ATC (Auto Temperature Compensation) which removes errors caused by temperature variance. All EC testers require calibration solution for proper calibration prior to testing.