Discussion of Selected Methods

Rhizon samplers are a hybrid device, which can be used in the laboratory, for example, pot experiments, as well as in the field (Cabrera, 1998 Knight et al., 1998). They represent one of the latest developments in terms of tension samplers, where it 

For the soil pore water sampling, the procedure described by Knight et al. (1998) and Tye et al., (2003) can be normally followed. Samplers are inserted into soil containers and soil pore water extracted by connecting a syringe to each sampler and applying a suction. 

Nominal data for physical characteristics and dimensions of the Rhizon samplers are given in Table 10.2. 

When suction is generated within the sampling system, water is sucked inwards through the pores of the sampler until a corresponding capillary pressure occurs in the pores. If the capillary pressure in the sampler is lower than that in the soil, water flows from the soil into the sampler until the capillary pressure in the sampler and in the soil are equal. The maximum capillary pressure in a pore can be calculated by the following equation (Schubert, 1982)  

1 Bubble Point tests are usually carried out to characterize a membrane or porous material consistency or quality they are also a common procedure to determine the maximum pore size. 

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