DEFINITION: Soil aggregates are clumps
of soil particles that are held
closely together by moist clay, organic
matter (roots ) and by organic compounds , form bacterial fungi and hyphea, aggregates are group
of soil
particles that binds together to
each other more strongly than adjacent
particles.
Soil
aggregates is the basic unit of soil structure
and its formation and stabilization has direct effect
on soil fertility
and crop production. Soil aggregates varies in size from about 2 thousand of a millimeter across up to
about 2 millimeter, and are made up of
particles of varying sizes, some of these particles do not fits closely together and this
creates spaces of many different
sizes ,these spaces or pores within the
aggregates are essential for
storing air and water, microbes nutrients and organic matte.
WHAT CAUSES AGGREGATION
Aggregation
occurs when particles are held together
by gravity, electrostatic forces,
various chemical glues (such as iron
oxides ) fibrous organic materials and a
range of gels and gums.
Thus
aggregation is the result of the interaction between soil texture and organic matter
Soil texture: This includes the types of clay mineral and soluble and exchangeable ions in soil
fluids sandy and slity soil is usually
weakly aggregated where as high clay soil is usually strongly aggregated.
Organic matter: The accumulation of chemical cement, time and the environment, plant
materials and root exudates are the primary source of
organic matter in soil, living organism and root might
comprise up to 15% of
total organic matter, while
active microbial population with
produce many adhesive by products which
helps in aggregate bounding
The
strength of bonding between
aggregates will determine soil strength, how the soil consolidates under pressure, the capacity of the soil to
absorb energy without eh aggregates
breaking down under mechanical cultivation and
resistance of the soil to erosion
A
well aggregated soil is
important it has pores between aggregates
and with aggregates, it has both large an some
pores. Large pores allows for the
exchange of oxygen and other gases in the atmosphere while small pores hold plants
available water and dissolved nutrients