Only about 50% of
the soil is solid materials, the
remainder is pore spaces, it is in this spaces, that water is stored
organism live there, organic matter
and nutrients accumulate thee, the
arrangement of soil particles gives a
porosity of 50% small pores with in the aggregates and the large pore
(tissures ) between the aggregates are
pathways for liquid, gases, roots and organism. The structure and layout of the soil both determines how activities in the soil happens, the rate at which they happen
and the capability to keep them
happening
The following characteristics are used
to help evaluate the ability of any soil to form a well aggregated structure
1.
Porosity: this is the pore space in the soil between
mineral particles and organic matter, filled with either air and water, the pore space contains and controls
most functions of the soil, ie storage pores retains water, while transmission pore
enables root growth and the movement of
air and water.
2.
Soil particles:
mineral soil particles comes from
rocks and sediments, the coarser materials are usually fragments of the
original materials while the finer are
usually products of usually products of weathering, the mineral particles are primary determinants of
soil structure
3.
Bonding and aggregation: the mineral component of a soil has the primary influence on how
soil particles binds together and therefore
what sort of aggregation
results, soil dominated by said tends to
bond weakly , clay soils bonds strongly but different clays gives
different bonding strengths.
The strength at
which aggregates bonds is impacted to
the soil by virtue of
i.
Cohesive
forces between particles
ii.
Frictional resistance meet by particles that are forced to slide over one another