soil health
Compost
How to determine good quality and the power of humus.
by Sam MacConochie
What is compost?
Humified compost is the process
of breaking down organic matter
into compost which is then
polymerized (a chemical reaction
to form three dimensional carbon
chains) by microbes and built up
microbially into humus (active
carbon); the result being a stable,
aerobic compost full of diversity
and population.
Humus can be considered as
the soil sponge; it soaks up and
holds onto moisture (more than
twice its own weight), nutrients
and provides the environment for
soil biology to flourish and feed
around the plant root zone.
Composting is powered by energy
via the microbial workforce
that generate and convert it to
breakdown organic materials and
build the compost up into chains
of carbons that form humus.
The break down of organic
materials (large molecules)
into smaller units of materials
(amino acids, phenols, peptides,
carbohydrates and enzymes)
explains the flow of energy
through a compost windrow.
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Humus consists of humic, fulvic
and olmic acids that all serve
different roles in the soil. For
example, fulvic acid is a huge
stimulator for nitrogen fixing
bacteria that will often foresee
significant legume growth.
The humus molecule containing
long chains of carbon-oxygen
molecules has the ability to
bind various nutrients such as
phosphate, nitrate and various
micronutrients, whilst coating
itself with amino acids and some
sugars to feed soil microbes
to encourage them to retain
nutrients and also encourage
nutrient cycling (conversion of
nutrients into plant available
forms by soil biology).
Good quality compost with a
strong humus component reacts
with chemical nutrients, thus
keeping individual nutrients from
antagonizing or tying up.
This method of nutrient delivery
expedites bringing base
saturation levels into balance,
which in turn positively impacts
the physical structure of the soil.
Compost, in conjunction
with proper livestock grazing
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management and rotation, crop
rotations, green manure crops
in fallow and less reliance on
chemical fertilisers and petrochemicals will re-generate all
characteristics of a balanced soil.
By boosting the biological
component of soil with quality
compost, the biological structure
will favour the microbe species
that are beneficial to plant
growth, yield and quality, and
unfavourable plant pathogens.
A common missing factor in some
southern Australian soils is fungal
biomass, which are vital for the
retention of calcium, carbon and
phosphorus. These types of soil
require fungal compost, in the
right ratio’s to bacteria and other
microbes to return the soil back to
biological balance.
With the essential biological
component in mind, the physical
structure of the soil’s tilth, porosity
and plant root penetrability will
encourage the flow of moisture
soil health
and oxygen through the soil;
while the biological component
will monitor the chemical nutrient
structure including pH, Base
Saturation balance, nutrient
retention and nutrient cycling.
The Building Blocks of
Plant Production
1. Conversion of energy and
carbon dioxide into carbon sugars
in the plant
Signs of high quality compost:
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2. Photosynthesis binds carbons
together
3. Carbon sugar pushed into root
system:
Winter crops= C3 plants (C-C-C)
Signs of poor quality compost:
•
Summer crops= C4 plants (C-CC-C)
4. Plant moves nutrients around
by binding carbon sugars to
other nutrients and convert it
into enzymes, amino acids,
proteins (nitrogen product) and
carbohydrates- and distributes to
where the plant needs it.
5. However, microbes around
the rhizosphere take up these
nutrients before the plant root
does.
So, improved biology ensures
the release of plant available
nutrients, feeding the root zone
for plant exudates to diffuse.
Over the past few decades, the
biological component of the soil
has been arguably depleted due
to some conventional farming
practices. Farmers are now
beginning to recognize the cause
of foliar disease, insect pests
and fertility problems that are
signaling something is wrong with
the soil.
No odour, the finished product will have a sweet smell
Dark brown earthy colour with only some parent material
remaining (less than 2cm) suggests the pile had sufficient
aeration in regard to the heating process to allow the flow
of oxygen and moisture through the pile.
A controlled process whereby developing the required
recipe and monitoring aeration, moisture management
and humification for maximum microbial diversity and
balance.
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Odour during the composting process is a sign of an
imbalanced compost C:N ratio where the bacterial
component is far too dominant and the carbon to nitrogen
ratio is incorrect.
Naturally black colouring is a key visual sign suggesting
the compost has gone through an excessive heating
process, resulting in a low oxygen environment
(anaerobic) causing a significant loss to vital nutrients
through volatisation.
White ash appearance in the latter stages is also a critical
sign of excessive heat (Actinobacteria).
E.Coli and other human pathogens (evident through
a biological lab test) suggests the compost has
suffered from limited oxygen and excessive heat;
hence encouraging the pathogens to out-compete the
Beneficial’s.
All biology must be present, in
full diversity, in the ratios that the
plant you want to grow requires.
Nutrient retention is the key
to maximising on-farm input
efficiency, converted into plant
available forms by soil biology.
Therefore, the flow of nutrients,
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water and oxygen in the soil is
increased for greater root growth
to protect the plant from disease
organisms.
Biological balance will ensure
nutrient balance and physical
structure, not vice versa- the key
transition from chemical farming
to re-generative farming.
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