Volumetric Water Content

VWC or volumetric water content is the unit measured by the 30MHz soil moisture content sensors. In this article, we have a short explanation what VWC is.

Volumetric Water Content (VWC) is the volume of water divided by the volume of soil. So, the VWC is the percentage of water in a soil sample. For instance, if a volume of soil was made up of the following constituents: 50% soil minerals, 35% water, and 15% air, that soil would have a 35% volumetric water content.

Soil Composition

The VWC values are higher/lower than I expect

It can be that the VWC values are influenced by the insertion of the sensors in the soil, make sure the sensor is installed correctly as described in this article.
Verify the numbers that you are expecting are according to the unit Volumetric Water Content (VWC) as the values are easily confused with Relative Water Content or Precent of Saturation. This can be done with a little help of our VWC calculator.

How can I verify that the measurements of my soil moisture sensor are accurate?

Verifying the VWC level of soil can be done by weighing a soil sample of a known volume. For this, you also need the weight of your soil in dried state. The larger part of the weight will be water.

As an example:

A 300ml substrate sample with a VWC value of 33% will contain 100ml of water and thus will weigh at least 100 grams, plus the weight of the soil in completely dry state (in my case 76 gram) for a total of 176 grams per 300 ml.

Please use our VWC calculator to calculate the volume of your sample.