YOUR SOIL
Soil loss is a threat to human survival
T
he United Nations has
declared 2015 the
“International Year of
Soils” and smallholders have
as important a role to play as
any landowner in preserving
healthy soil and rehabilitating
soil when necessary.
All soil is composed of
mineral particles (sand, clay
and silt), organic matter, air
and water.
It is a “living” system in that it
breathes. However, it is
extremely fragile.
The most productive (fertile)
part of the soil is only a
couple of centimetres thick
and this is usually the part
that is eroded first. Soil
scientists inform us that 2,5cm
of topsoil takes between 500
and 1 000 years to form.
Not surprising, therefore, that
today soil is a threatened
resource, precisely because
soil erosion is so pervasive
and hard to reverse.
Rich soils form a vital part of
our ecosystems by storing and
cleaning water, and keeping
our climate stable.
But because of large scale,
single crop, industrial
agriculture, farmers have been
managing their farms like
factories, in pursuit of
maximum profit.
They are focused on maximising yields, but often at great
cost to the land itself.
Smallholders are also guilty of
ploughing and loosening their
land every year and “enjoying” in many cases an
ongoing addiction to chemical
fertilisers and pesticides.
These in turn carry nitrogen
and phosphorus as well as soil
into our water systems and
into the sea each year.
Landowners too have
sometimes failed to nurture
and strengthen our soils, the
valuable soils on which our
food production relies.
Topsoil is the layer that allows
plants to grow and globally at
current run-off rates we have
only about 60 years of topsoil
left, say researchers.
Half of the topsoil on the
planet has been lost in the last
150 years. In South Africa it is
estimated that 300 to 400
million tons of soil are lost per
year. Nearly three tons per
hectare of land per year for
every ton of maize, wheat or
sugar produced.
In South Africa 40% of all
cropland suffers from land
degradation. Population
pressure is going to exacerbate this issue as more and
more marginal soils are put
into cultivation.
Overgrazing is responsible for
about half of the soil degradation in Africa.
Overgrazing leaves soils bare
of vegetation, at the mercy of
the elements. It also compacts
Continued on page 15
Erosion is responsible for the loss of 300-400 million tons of SA soil a year.
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