FARMACY Healthy Soils - Page 2

The Healthy Soils Concept
Good soil health is fundamental to agricultural productivity and sustainability.
Although soil health is predominately seen as a function of biological activity,
it is influenced by the dynamic interactions that occur between the physical,
chemical and biological components of the soil.
Chemical components
Of particular importance for soil
health is the impact soil chemistry
has on the development of plant
microbe interactions. For example,
soils based on limestone have
a tendency to be rich in calcium
and be alkaline, which can restrict
the uptake of nutrients such as
phosphorus and manganese. This
can reduce root mass and limit root
exudate production, restricting both
microbial activity and plant response
to microbial growth promotion.
Soil chemical properties also regulate
microbial growth rates directly
through nutrient availability. This
affects the rate at which microbes
release plant available nutrients.
Physical components
Biological components
During its conversion from plant
and animal residues to humus, soil
organic matter has a direct impact
on soil health. Undecomposed
organic material provides a food
source for macro-organisms such
as earthworms. Worms mix partially
decomposed organic matter with
soil minerals as it passes through
the gut, creating channels for air and
water movement in the process.
Microbes thrive in worm casts,
completing the conversion of organic
matter to plant available nutrients
and humus.
Humus organic matter is in the form
of long chain polymers, capable
of binding sand, silt and clay into
stable soil aggregates, while at the
same time providing exchange sites
for nutrients and improving water
retention. This results in increased
soil fertility and yield potential.
Humus also provides a long-term
source of energy and nutrients for
beneficial fungi and bacteria.
The physical properties of a soil
are determined by the balance
between sand, silt and clay
particles, which determines texture.
These particles combine with
various forms of organic matter to
form soil aggregates. The size and
distribution of these aggregates
determines soil structure.
Soil structure directly affects the
movement of air and water through
the soil profile, which in turn affects
biological activity, root development,
crop establishment and tolerance to
environmental stress.

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