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The retention curve illustrates the relationship between water content and soil water tension. This relationship is characteristic of each soil type and is influenced by various factors. One of the most important factors is the pore size distribution. This is closely related to the soil type, which is why it is common to specify typical retention curves for different soil types. The figure shows retention curves for sand, silt [...]

When we talk about soil moisture, we are referring to the water content. This indicates how much water is in the soil. The water content can be specified in two different ways. The volumetric water content is the ratio of the volume of water to the total volume of the soil sample. The gravimetric water content is the ratio of the mass of water to the mass of the dry […]

A detailed description of the structure and function of watermark sensors can be found, for example, in the following scientific article, which also serves as the source for this article: "Irrometer Watermark Series: Scientific Background" from Mississippi State University. At the heart of a watermark sensor is a measurement of the electrical conductivity between two electrodes. If there is non-conductive material between these two electrodes [...]

The patented Watermark sensor for determining soil water tension in kPa has been in use worldwide since 1978. But what exactly is soil water tension? Soil water tension refers to the force with which water is retained in the soil. It is measured in units such as centibars (cb) or kilopascals (kPa). This tension is caused by the attractive forces between the [...]