Home' Grower : May 2011 Contents The South Australian Grower -- May 2011
TRIALS in Riverland citrus
orchards continue to demon-
strate that soil amendments
pay off in more ways than one.
SARDI senior research scientist
Peter Crisp has been r unning trials
examining their benefits for the
past five years.
"There's been lots of research
into soil amendments and soil
organic carbon in broadacre crops,
but limited information in orchard
crops, such as citrus," he said.
The research started in 2006
with a three-year project to test a
range of soil amendments, includ-
ing grape marc, animal manure
Yield increases between 17 per
cent and 63pc were recorded in
2008. A study in valencia oranges
achieved similar, if not slightly bet-
"We were amazed at the yield
improvements we recorded -- they
were way above our expectations"
Dr Crisp said.
"Increases in yield were due to
higher fruit density on the trees, as
well as increasing fr uit size.
"The compost industry saw ben-
efit in this initial research and in
2009 wanted us to pick up where
we left off."
Funding from Compost for Soils
Horticulture Australia Limited to
continue the research for three
more years, during the 2006-08
In trials with navel oranges, they
have continued to record yield
increases in the 2009 and 2010
seasons on trees for all types of soil
As in 2007 and 2008, increases
in yield were attributed to fruit
weight and density. Fruit diameter
also increased in navels when soil
amendments were applied.
"An increase in fruit diameter
adds to the value of fresh fruit that
is destined for high-value mar-
kets," Dr Crisp said.
"Going up a size class could
mean an increase of $100 a tonne
In valencias, the effects of soil
amendments have been mixed in
the past two years. Trees treated
generally yielded less than untreat-
ed trees in 2009.
Dr Crisp said this could have
been due to high yields in 2008
and the impact of water restric-
tions in 2009. In 2010, as in 2007
and 2008, yields from trees with
composted green organics were
significantly higher than untreated
Results were less consistent when
composted animal manure and
grape marc -- instead of composted
green organics -- were used.
"There are two contributions to
improved income for growers,
more fruit or bigger fr uit.
Therefore higher fruit weights and
bigger fruit means a higher price
per tonne," Dr Crisp said.
A major component of the
research included developing a
benefit cost-analysis which took
into account herbicide and fertilis-
er savings and the additional cost
of fruit har vesting.
During the five-year period
assessed so far, there have been
considerable economic benefits
with each type of soil amendment.
"For ever y dollar invested in soil
amendments, returns ranged from
$1.91 to $5," Dr Crisp said.
It was likely the yield benefits
with soil amendments were due to
improvements in soil structure,
cation exchange, bulk density and
"Improved water-holding capaci-
ty in soils would also have had a
major influence on yield," he said.
Further monitoring would con-
tinue at the trial sites to examine
whether different application tim-
ing or lower rates continue to pro-
duce yield and size increases.
Details: Research details Peter Crisp,
SARDI, email@example.com or com-
post contact Kaylee Maitland, Compost
for Soils, 7329 0422, or visit
The research started in 2006 with a three-year project to test a range of
soil amendments, including grape marc, animal manure and compost.
Pay dirt for amendments
in extensive citrus trials
Onion roadshow visits SE
THE South East onion industry recently showcased its credentials to an
international tour group.
Seed distributors and representatives from throughout the world were part of an
onion roadshow inspecting freshly-harvested new trial varieties -- and the visitors
liked what they saw.
The international contingent visited SE sites before heading to Adelaide and
New Zealand as part of their study tour.
While in the region, they visited various farms, packing sheds and a peeling
facility, and also took the opportunity to meet with Onions Australia
representatives, including OA executive officer Joanne Thomas-Ward, who is
based in Mount Gambier.
The tour -- organised by Terranova and Enza Zaden -- comprised 30 people from
Chile, Argentina, Brazil, South Africa, Holland, NZ, the United States and Australia.
Terranova SA territory manager Greg Bragg said the visit was extremely
successful, with Enza Zaden production staff, customers and suppliers inspecting
new trial, commercial and existing varieties.
"We were very interested in seeing how they were progressing in line with the
current standard," Mr Bragg said.
"It also assisted to ascertain which varieties we are going to progress with to
The international contingent visited
SE sites before heading to Adelaide
and NZ as part of their study tour.
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