YOUR SOIL
Humus: why it’s important in your soil
A
ll gardeners have
heard of humus, and
most probably
associate it with decomposed
plant material, usually the
result of some composting
process.
While that's quite correct, a
better and more detailed
understanding of what humus
is, and how it works in the
soil, will give a greater
appreciation of its importance.
Humus is a complex and
rather resistant mixture of
brown or dark brown
amorphous and colloidal
organic substance which
result from microbial decomposition and synthesis and it
has chemical and physical
properties of great significance to soils and plants.
The humus compounds have
resulted from two general
types of biochemical reactions: decomposition and
synthesis.
As part of the decomposition
process chemicals in the plant
residues including lignin are
broken down by soil
microbes.
Other simpler organic
compounds that result from
the breakdown take part
immediately in the second of
the humus-forming processes,
biochemical synthesis.
These simpler chemicals are
metabolised into new
compounds in the body tissue
of soil microbes.
The new compounds are
subject to further modification
and synthesis as the microbial
tissue is subsequently
attacked by other soil
microbes.
Synthesis involves such
breakdown products of lignin
as the phenols and quinones.
These monomers undergo
polymerization by which
polyphenols and
polyquinones are formed.
SOIL BIO-MUTI
Cucumber grown with SBM
From page 20
mortalities out of 250 birds,
the cages were dry, the manure
less smelly and fewer flies were
present.
Sheep are said to produce
better quality wool and more
meat when dosed with SBM.
SBM is available in quantities of
5 litres, 25 litres and 210 litres
and is used diluted or neat
depending on the application.
Distributors are also sought
throughout Gauteng.
For more information contact
Fred Daly on 082 804-3130.
21
www.sasmallholder.co.za
These high molecular weight
compounds interact with
nitrogen-containing amino
compounds and form a
significant component of
resistant humus.
Colloidal clays encourage
formation of these polymers.
Generally two groups of
compounds that collectively
make up humus are the
humic group and the
nonhumic group.