Focus on Fodder - Australian Fodder Industry Association

...compost for the 21st century
Continued from page 1
For a soil to be healthy, we know we
need the component parts to be
healthy—its chemical, biological and
physical properties. These properties
determine how well the soil functions
– how it drains, holds water, holds
nutrients, and how well it grows
pasture or crops.
As the diagram (below) shows how
organic matter (OM) is central to the
soils condition. It performs critical
roles in the biological, physical and
chemical functioning of soil and helps
to maintain conditions conducive for
plant growth. OM:
is the food that sustains soil
organisms;
contains most of the nutrients in the
soil that sustain plants;
holds nutrients in such a way that
plants can access them;
forms bridges with the clay
component of soil to provide
structure; and
holds water and makes it available
to plants.
Physical functions
• influences soil structure, stability
• regulates water holding capacity
• controls gaseous exchange
• alters soil thermal properties
page 16
Biological functions
• drive nutrient cycling processes
• drives carbon cycling
• source of energy
• reservoir of nutrients
organic matter
In fact, OM is so important our soils
would be dead without it.
There is growing awareness in
agriculture that we need to manage
OM better than we have in the past.
Research has shown that OM levels
decline sharply following land clearing.
In fact, every time we cultivate land
we stimulate the degradation of OM.
The good news is that this is usually a
slow process; the bad news is that it
is equally slow if you want to re-build
levels of OM in your soils.
Building OM involves a range of
strategies. You can grow it (perennial
pastures), spread it (animal
manures), or make it (composts). All
strategies have their place and all
have advantages and disadvantages.
Growing it is great but is slow, so long
as you don’t cultivate that paddock. If
you do OM is likely to decline faster
than it accumulated. Spreading it is
great too, and quicker than growing it,
but you have to have access to good
quantities of manure to make it work.
Chemical functions
• cation exchange capacity
• buffers changes in pH
• storage/cycling of nutrients
• complexes with soil organic C
AFIA Newsletter Winter 2012
On Farm
Making compost with low quality hay.
Composting is also an excellent way
to increase OM. Advantages include
its soil improvement properties,
nutrient status and affordability, if
you have access to the raw materials.
Disadvantages generally surround
making and handling compost.
However, a growing number of farmers
are exploring the options of making
or buying in compost, and using it
in conjunction with their inorganic
fertilisers to boost soil health and
maintain productivity.
Trying to make compost on farm is a big
hassle only if you are not properly set
up, and if you don’t do it properly. But
farmers who have invested the time
and effort to get set up are reaping the
benefits, with most reporting some
improvement in their farming system.
Improvements include soil condition,
animal health, product quality and
profit. Well set-up farmers report costs
in the order of $100–250 to make and
spread 3 t/ha compost.
Probably the most important thing
for commercial scale composting is
owning, or having access to, a compost
turner. This single factor is largely
responsible for the growth in compost
use in places like the South West,
Gippsland and North Central areas of
Victoria, where contractors are making
turning services available on-farm.
You can make compost quite well
with a front-end loader–in fact it is
recommended that you start that way
on a small scale while you develop a
‘brown’ thumb. Select a small area–
say 1-5 hectares of average land, not