Home' Grower : July 2011 Contents The South Australian Grower -- July 2011
Trade exhibition to
Trade Expo will be
a major feature of
conference at Adelaide Convention Centre from
It will be open from 1pm to 5pm on Sunday,
with free entry for growers.
More than 50 exhibitors, representing a who's
who of the horticultural industry, have
The trade displays will cover new varieties,
green/glass houses, fertilisers, irrigation and
nutrition, growing media, pest and disease
Leading companies, including Hortus Technical
Services, Kubo Greenhouse Projects, Proptec,
Rijk Zwaan Australia and Syngenta, will also be
available to give expert advice.
About 350 registrations are expected for the
conference and workshops, with about 30
Australian and overseas speakers -- many
leaders in their respective fields -- scheduled to
PCA is the peak industry body representing
the interests of commercial greenhouse and
hydroponic growers, an industry valued at about
$1.3 billion at the farmgate.
The industry consists of commercial outdoor
and protected cropping growers of important
crops including tomato, cucumber, capsicum,
eggplant, lettuce, Asian vegetables, herbs,
strawberries, and a wide range of cut flowers,
together with allied trades.
Details: Rick Donnan 02 4567 7960, pcaconfer-
Invest in your own
BY ANGELA LUSH
MOST of us know that soil
organic matter and the
organic carbon it con-
tains is important for maintain-
ing a healthy soil.
What I didn't know, was that
different types of crops can have
very different affects on soil
organic carbon levels.
Recently, I attended the
International Symposium on
Organic Matter Management
and Compost Use in Horticulture
in Adelaide where I heard Elke
Schulz speak on this topic.
From the Helmholtz Centre
for Environmental Research in
Germany, Dr Schulz reported
on trials investigating how dif-
ferent crop types affect soil
organic matter dynamics.
Soil organic matter is largely
made up of soil organic carbon,
and carbon levels are used to
estimate the amount of soil
organic matter in the soil.
The trials examined the
amount of organic carbon that
legume, cereal and vegetable
crops added to or removed from
the soil. The results of these tri-
als can now be used by farmers
to better balance soil organic
carbon levels in their soils.
Crops such as legumes and
grasses contributed carbon to
the soil. Grasses and legumes
added about 700 kilograms of
soil organic carbon a hectare per
year. Winter cover crops added
That is why these crops are com-
monly used as cover crops and
green manure crops to maintain
and improve soil health.
Potatoes, cauliflower, Chinese
cabbage, cabbage, tomatoes, leek
and cucumbers depleted soil
organic carbon, removing a stag-
These crops were categorised as
high carbon-depletion crops.
Carrots, sweetcorn and capsicums
700kg/SOC/ha/year on aver-
age, while head lettuce, onions,
spinach, cereal crops and oil seed
crops were classed as low soil,
organic carbon depletion crops.
The difference in carbon
removal between some of the
vegetable crops was as great as
600kg/year (leeks-high, onions-
low). Growers can now take this
information into account when
they plan their crop rotation and
Dr Schulz also reported on tri-
als examining the carbon con-
tent of a range of organic
amendments that can be used to
replace soil organic carbon.
Composted manure, bark
compost, fresh compost and
straw contained the highest lev-
els of organic carbon (kg/t).
Pig and cattle slurr y and poul-
try manure contained the lowest
levels of organic carbon.
The stage of maturity, dry mat-
ter content and composition of
the organic amendment all influ-
enced organic carbon levels.
The most stable supply of
organic carbon was found in
Dr Schulz stressed the impor-
tance of taking a long-term view
when looking at soil organic
carbon because soils, and partic-
ularly soil organic carbon levels,
often respond very slowly to
changes in management.
The benefits of rotating vegetable
crops with legume crops or apply-
ing organic amendments, such as
compost, can often take a while to
show any effect on the soil.
Dr Schulz outlined a simple
equation for maintaining a good
balance of soil organic carbon: soil
organic carbon removed by crop
(through har vesting) + soil organ-
ic carbon replaced (organic
amendments added) = soil organ-
ic carbon balance.
index or www.ufz.de/index
Potatoes, cauliflower, Chinese cabbage, cabbage, tomatoes, leek
and cucumbers depleted soil organic carbon, removing a staggering
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