Moisture retention characteristics curve illustrates the relationship between soil water tension and moisture content of soil. Soil water tension tells us how tight water is attached to soil matrix. For example, when we say “soil water tension is 0.3 bar” it means that for extracting water from the soil, one needs to apply a pressure (or tension) more than 0.3 bar to the soil. 

There are several methods to come up with soil moisture retention curve. Soilmoisture Equipment Corp. (SEC) has been manufacturing various laboratory setups for measuring moisture retention curve for about 60 years. That is why you can see SEC instruments in numerous publications and even ASTMs. Because of its superior product quality, SEC has developed a reputation among scientific community. SEC instruments are considered almost as the standard method of doing soil moisture retention measurements.

Basic concepts and components

Based on several years of experience in SEC, I know that buying a moisture retention lab (MRL) setup is a complicated and sometimes even overwhelming process. People have very different needs, there are many technical details to consider, and several options are available.