Why is it important to have well structured
soil? A well structured soil will allow
water to gradually flow through it.
As the water passes down through the soil profile, it
creates a vacuum, and so fresh air is drawn into
the soil, thus creating aerobic or oxygen rich conditions.
This is crucially important as the majority of
disease causing microbes cannot operate in oxygen rich environments,
and they are forced to shut down.
Meanwhile, beneficial microorganisms thrive
in oxygen rich environments.
Water droplets are held in numerous cracks and
crevices and in organic matter for long periods
of time, thus increasing drought resistance.
Good structure allows plant roots to move
effortlessly through the soil profile without having
to work hard against compaction layers.
In soils where good structure has not been built
by beneficial microorganisms, compaction layers are easily formed by
vehicles, by human and animal traffic, and where the
soil surface is left bare by rainfall. Compaction layers
force plant roots to grow sideways, limiting their access
to nutrients and water.
When plant roots break through compaction layers,
they encounter anaerobic or low oxygen conditions.
Those are occupied by anaerobic microorganisms,
which produce highly acidic compounds.
Roots cannot survive in such conditions where
the PH can be lower than four.
When water flowing through a soil meets a compaction layer,
it can't get through and so in heavy rain, this
can result in a saturated layer of
soil sitting on a hard, compaction layer.
If there is an incline, the topsoil can
start to move, resulting in a landslide.
This type of soil erosion is a big
problem in many places around the world.
So how is good structure built by the Soil Food Web?
Well, this depends on the type
of soil we're dealing with.
The term sand, silt, and clay describe
the size of the soil mineral particles.
Sand particles are relatively big and so
are the spaces in between them.
Water quickly finds its way through the gaps and
not very much water is retained, especially if the
organic matter content is very low, as organic matter
can absorb huge amounts of water.
So Sandy soils tend to be very dry and
are prone to wind erosion, which is the process
by which the topsoil is blown away and lost.
Soil erosion is a serious environmental problem and poses
an existential threat to humanity as we only have
around 60 years of topsoil left in the world,
according to recent estimates. With the Soil Food Web
in place, the picture rapidly changes.
Beneficial bacteria produce sticky compounds or glues, which
make it easy for them to adhere to
the surfaces of organic matter and sand particles.
These particles then adhere to
one another, forming microaggregates.
Notice how as things clump together,
small spaces are created around them.
Fungi also produce some glues, and their
long, narrow tubelike structures act like ropes,
tying together the microaggregates to form macroaggregates.
Now, even larger spaces are
formed in the soil structure.
When microarthropods, earthworms and insects burrow
through the soil, they create even
larger spaces like tunnels.
All the while, the Soil Food Web is
increasing soil organic matter in the soil profile,
by decomposing the surface litter into humus and
transporting it deeper and deeper into the soil.
Soon you can dig down and discover layer
after layer of dark chocolate brown soil where
there was once only lightly colored sand.
The result is a structure that will hold
water for several months after the rains have
stopped, making it available to plants
in times of drought. Roots are able to dig much
deeper and to access more water and nutrients in parts
of the soil that were never available to them before.
In essence, the subsoil has now become topsoil. Dr.
Ingham and her team have worked on landscapes such as
pastures, turfed lawns, and golf courses, where the grass roots
were only able to grow an inch or so into
the soil because of the presence of compaction layers.
In just a few short months after the
Soil Food Web is restored, those same roots
are able to grow more than 3ft deep
accessing more water and nutrients than ever before.
In clay soils, the problems are a little different.
Clay particles are often referred to as platelets,
as they are kind of round and flat
like the plates you have in your kitchen.
Without a balanced Soil Food Web, these
platelets get stacked up on top of
each other, forming very tightly compacted structures.
Compaction layers can form very easily in clay soils.
The solution to this problem is finding a way
to get those clay particles to stop stacking.
This can be achieved by a process called flocculation.
Flocculation occurs when sufficient positively charged
calcium ions are present on the
surface of the platelets.
This results in them repelling each
other just like magnets do
when their poles are aligned. The Soil Food Web increases
flocculation and once this is achieved, structure can be built
in just the same way as with sand particles.
The result, once again is a well structured
soil that enables plants to access more
water and nutrients than ever before.
For farmers, this means increased yields, cost savings due
to reduced irrigation requirements, and even further cost savings
as there is no longer any need to plow.
Lower costs and increased yields result
in greater profits. For the environment
there are a number of benefits.
A well structured soil that is home to the Soil Food
Web purifies water as it passes through the soil profile.
This is because any contaminants in the water are seen
by bacteria and fungi as nutrients and are rapidly absorbed
into their bodies as the water passes by.
Soil erosion by wind and water are greatly
mitigated, offering food security to future generations.
And finally, water vapor is one
of the most abundant greenhouse gasses.
By enabling more water to infiltrate the world's soils
and to flow into aquifers we may be able
to contribute to the fight against climate change.
For more information about the numerous benefits
of the Soil Food Web and how
You Can Get Involved visit soilfoodweb com.