How does the Fertometer work?

de fertometer is een handige tool

The Fertometer uses the process of electrolysis and is also referred to as an EC-meter (Electrical Conductivity) in technical terms.

The Fertometer works on the same principles as a plant. Like the roots of a plant, it absorbs nutrients from the soil. By measuring the quantity of the absorbed substances, it can be determined whether there are sufficient nutrients left in the soil. These absorbable nutrients are called ions and consist mainly of nitrogen, the principal nutrient for plants during the growing season. All ions are involved in the measurement, so as to get a good indication of the amount of fertiliser in the pot. It is, though, not possible to recognise from the measurement if a plant is lacking other elements such as potassium or magnesium.

An EC-meter reads and interprets an electrical current. This interpretation could be visually represented by an analogue or a digital display. In the case of the Fertometer, a clear and simple indication of the result has been chosen using three lights.

Definition of the measurements used

Measurements are expressed in EC-values (Electrical Conductivity).

These EC-values, measured in mS/cm (milli-Siemens per centimetre), are converted to three digital values that have been designed for ease of use: in what we shall call the 'green band', sufficient nutrients are available. In most cases, the potted plants are lacking in nutrients and results will be in the 'yellow band'.

In some descriptions of EC-values other units are used. American practice uses dS/m (deci-Siemens per meter) or mmhos/cm (milli-mhos per centimetre). 1 S is equal to 1/Ohm, the inversion of ohm (mho).

EC is the conductivity of an electrical current through one centimetre of medium. In this case, the medium is soil. Per definition, one should obtain a reading of 1mS/cm, if the medium's salt content measures 620ppm (parts per million). Another much-used scale is g/l (gram per liter), 620ppm = 620mg/l = 0,62g/l.

Temperature dependency

The EC-measurement is dependant on temperature. The Fertometer is set at a standard of 20C. Results are the most accurate if obtained around this temperature. Lower temperatures will result in lower EC-values, whereas higher temperatures will lead to increased values (2.2% per C).

Accuracy of measurement

The accuracy of the Fertometer depends mainly on the quantity of water contained in the soil. If the soil is 100% saturated, the result will be the most accurate. Up to 70% saturation, they will still be reliable, but if the soil is drier, the results are no longer usable. The conductivity of the soil will be impaired. To be confident that the soil is adequately wet, water the plant 30 minutes before use.

The accuracy of the measurements is not affected by the electronics or the analogue/digital transformation.