Extracting water from the spaces and pores in soil is important research for anyone involved in crop cultivation. For general soil water extraction, especially when larger volumes of samples are required we recommend ceramic cup samplers. These are a good and cheap method of sampling soil solution and work well when simple analyses such as nitrates, chlorides, bromides, sulphates and sodium are needed. Different lengths are available for sampling to different depths in diameters of 31 or 63mm. You can collect a large amount in a relatively short period of time and the construction is contaminant free.
The downside of these samplers is that the ceramic cups can interfere with the chemistry of certain elements, compounds or measurements such as, for example, pH and Phosphorus and other metals and they are not frost resistant.
Our supplier Eijkelkamp has a huge amount of information on this type of research and we would recommend looking at their presentation of soil moisture sampling which can be found here or call us on +44 (0)1428 661 660 and talk to one of our experts