Rhizosphere Controls Hydraulic Interaction Report

METHODOLOGY
How the rhizosphere controls hydraulic interaction between the ground and the
atmosphere and implications on mechanical performance of geo-structures.
Introduction
The plasticity of rhizosphere is defined by the dynamic alteration of the bimodal water
distributions. The presence of increased water content in the rhizosphere has been as a result of
hydrated mucilage, air-filled gaps and temporarily hydrophobic rhizosphere. This basically the
gap between the roots and soil which promotes infiltration processes and percolation. The
plasticity is therefore treated as a plan to be used in control of the production of mucilage that
has since form part of the system of root and will have facilitated water access. In order to have
such kind of dualism explained the rhizosphere must be classified into at least to categories.
The first category of classification of the rhizosphere is called class A rhizosphere. This
particular category is covered with mucilage which is hydrated. The class A rhizosphere is
responsible for the root connection to the soil optimally besides facilitating the flow of water to
the plant’s roots as the soil continues to dry up. The next category of rhizosphere is the class B
rhizosphere. It refers to the air-filled gaps and in some cases it is made up of a mixture of air and
water or being hydrophobic. Due to this hybrid composition, this kind of the rhizosphere
disconnects the roots from the soil. The disconnection can be temporary and the hydraulic
contact becomes partially recovered according to the history of wetting or drying. In the case of
class B rhizosphere can assist in the prevention of water loss from the roots which are later
transferred to the soil. It is thus expected to predominantly cover roots which again are
responsible for the long term distance transport. The root segments share which belongs to class
A and B which are very dynamic. This happens despite the values of mucilage being produced
primary at the tips of the roots.
Controversy has since remained about the role which is being played by the mucilage as far as
water holding capacity is concerned. This has to do with the question whether mucilage which is
exuded decrease or increase the water holding capacity in the soil itself. In mucilage, there are
components which act both as sponges which have higher capacity of water holding as well as
other components which act as surfactants and hence becoming or gaining hydrophobic

properties upon drying up. The importance of these two substances tends to vary significantly
with time under the growing conditions and as a function of the species of the plants. Mucilage
will therefore increase the water holding capacity of the rhizosphere, which is found nearly close
to the roots of young plants. This is so common particularly for those plants which are found
between the ages of 2 to 4 weeks and are growing in sandy soils.
The rhizosphere will be temporarily hydrophilic especially once it has dried up. This implies
that mucilage can temporarily decrease the water holding capacity of the soil after it has been
dried. These two facts should never be viewed as contradicting approaches to the solution
concepts. Instead, they should be regarded as an expression of the plasticity of rhizosphere as
well as its dynamics of time. The primary question is how such kinds of rhizosphere can be
extended to the plasticity from the whole systems of the roots as well as evaluation of the effects
of the scale of the plant. The idea of most of the scholars is that properties of rhizosphere usually
have bimodal distribution with a class of rhizosphere as A which assists in the description of the
proper contact between the roots and the soils. The classifications of the properties of
rhizosphere as well as assignments to the classes of roots as A and B will be a factor of the
production of the mucilage, degradation rate of the same mucilage, conditions of growing as well
as variation among the species of the plants. Classifications thus consider class A to be
dominated or be common among the young roots which again are more distal. Also the
rhizosphere of class B is expected to be associates of the older proximal roots. This is as per the
shared explanation below
There are two categories of the soil profile based on its relative location to the water table
(phreatic surface). The soil profile that exists below phreatic surface is known as saturated zone.
This zone experiences high water saturation and has positive pore-water pressure. Vadose zone is
the name given to the soil profile that is above the phreatic surface and it has low water
saturation levels.
Geotechnical structures interact with the soil profile that has unsaturated, this is the zone located
above the phreatic zone of the soil profile. A good example is the surfaces of the unstable slopes
that often develop on the unsaturated zones. The unsaturated profile of the soil (upper profile),
have stiff soils with relatively high shear strengths compared to the soils located below the
phreatic surfaces. This unsaturated region interacts mostly with the atmosphere. Atmospheric

conditions and climatic conditions such as precipitation, rainfall and evapotranspiration normally
lead to a situation in which fluctuations occur as far as saturation degrees and pore pressures is
concerned. Such occurrences have a direct effect on geo-structures. (Wallenstein, 2017).
In engineering practice, the prediction of soil responses in unsaturated environments is widely
recognized. By taking into account the nature of soil saturation, it makes it easy to be able to
predict the climatic effects on geo-structures. An example is the effect that rainfall has on the
stability of natural slopes and man-made ones, among various geo-technical structures. Another
example is the effect that drought brings about on foundation subsistence.
The unsaturated soil profile constitutes the rhizosphere and is considered to be the vicinity of
roots. The hydraulic characteristics and behavior of the rhizosphere can be determined using
various methodology. This implies that hydraulic interaction between the ground and the
atmosphere can be determined by studying the main aspect which is the rhizosphere in which
there is direct effect on the atmosphere in terms of evaporation and evapotranspiration (water
saturation).
The main aspects include;
Water retention
In the rhizosphere, water retention can be measured by taking measurements of pore water
pressure and gravimetric water content (volumetric water content). This can be done on soil
samples that are undisturbed either in the laboratory or in the field. Field measurements can be
done by the help of sensors installed in ground soils. The characterization of water retention by
experimental means takes quite a lot of time thus the alternative of using value form existing
literature and common values can be taken into consideration. Several volumetric variables can
be used to represent water retention as shown below;
Gravimetric water content w= M water
M solids
Water ratio ew= V water
V solids