Soil close to roots generally has chemical, physical
and biological properties which are significantly
different from those of soil located some distance
away (Jenny & Grossenbacher 1963; Hawes &
Pueppke 1986; Young 1995). The root–soil interface
is defined as soil near to or adhered to the root surface
to some small distance into the soil matrix. This
distance may vary between <1 mm and c. 10 mm.
Working definitions include rhizosphere, where ‘zones
of influence’ are inferred, and rhizosheath, when soil
adhered to the root is discussed. Most work carried
out at the root–soil interface has concentrated on
biological or chemical processes, due both to the fact
that the relevant techniques required to examine these
processes have been more advanced than the physical
techniques, and also because the farmer is generally
offered either biological or chemical solutions to his
everyday problems, as these are readily accessible,
easy to use and cheap. The main manipulation of soil
physical conditions occurs during cultivations, and
the addition or removal of water from the soil profile.
Intensive cultivations are a regular occurrence in
many farming systems, despite the potential drawbacks:
damage of the soil structure, leading to reduced
crop yields and an increased risk of erosion.The main aim of this review is not to cover all the
complex issues related to the root–soil interface.
Instead, it concentrates on the biophysical processes
which, compared with conventional plant physiological and
soil microbiological research, have
attracted relatively limited attention (e.g. see Waisel
et al. 1996). The review examines small-scale
(μm-mm) interactions and, where possible, links their impact
to the larger scale. Three interacting areas are investigated:
the physical structure of the soil and root
growth, water dynamics and microbial dynamics.
Scientific Opinion on the assessment of dairy cow welfare in small‐scale farming systems
