oIn addition, plants, as living organisms, modify the environment
they live in and, in particular, plant roots alter the surrounding soil
(i.e. rhizosphere; e.g. Hinsinger et al., 2009) inmanyways. These changes
are demonstrated not only as enhancements of the soil matrix structure
and strength but also as alterations of the mechanisms governing
soil physicochemical processes, such as the retention and flow of
water in the soil (Carminati et al., 2010; Scholl et al., 2014). Hence,
when plants are present in the soil one should consider a new material
(i.e. plant-soil composite) with specific hydro-mechanical properties
(Scanlan, 2009). However, testing the properties and behaviour of
plant-soil composites, in general, and soils under unsaturated conditions,
in particular, is difficult – there is a need to develop simpler and
quicker protocols.