team Jack Desbiolles and Dean Thiele with the UniSA specialised plot seeder
designed to enable comparative evaluation of commercial seeding system
Choosing a seeding system suited to growers’ specific needs
can have significant benefits in crop performance.
University of South Australia agricultural research engineer
Jack Desbiolles has spent years studying the impacts of seeding systems on crop
performance under different soil types and residues.
“Getting the seeder set-up right is critical for rapid seed
germination, uniform crop emergence and good early vigour,” he said. “Due to
the diverse nature of soils and climatic conditions there is no one-size-fits-all
Through the Agricultural Machinery Research Design
Centre (AMRDC) at UniSA, Dr Desbiolles has conducted GRDC, SAGIT and DAFF-funded
research into optimising seeder set-up in no-till systems.
Seeder Set-up Guide
As part of the GRDC stubble initiative, Mallee Sustainable
Farming and Dr Desbiolles have compiled dedicated guidelines on seeder
technologies including a simple table to assist Mallee grain growers in
selecting the right seeding configuration for their situation.
Figure 1: Seeder Set-up Guide (download the full-size table)
Paired row systems for variable soil types
“One of the challenges Mallee growers encounter at seeding
time is the inability to maintain a consistent and accurate seeding depth across
all soil types in the paddock,” Dr Desbiolles said.
“As a result crop establishment is often variable with crops
sown too shallow on the stony soils and too deep on the sandy hills, which
significantly impacts crop emergence, erosion risks and ultimately crop
Research by the Minnipa Agricultural Centre during 2007-09
found that both tyne and disc seeders could be used effectively in stony soils
as long as the settings were optimised; getting the settings wrong, such as too
shallow seeding depth in dry conditions, reduced establishment by up to 40 per
Seeding system comparison trials conducted at Murrayville in
the Victorian Mallee during 2014 identified that paired row systems gave the highest
and most consistent wheat crop establishment across three soil types (Figure 2),
after very good soil moisture conditions at sowing.
Figure 2: Murrayville, 2014: Wheat crop
establishment pattern over 12 subplots along 3 soil types in a swale dune
context, for better performing seeding systems relative to a district
Seeding systems were compared to the district technology of
a simple chisel tine with knife point, rubber seed boot and narrow press wheel.
In terms of emergence, the benefit of paired row systems ranged from 15 per cent
on the mid-slope and sand hill, to 20 per cent on stony soils. Under a dry season finish, the paired row
systems gave 0.05-0.15 t/ha improvement in wheat yield, with the largest
benefit on the stony flat.
A more advanced seeding system featuring a gauge wheel
regulated seed delivery independent from the furrow opener also performed
better in the stony flat, with 17 percent higher crop emergence and 0.1 t/ha additional
Dr Desbiolles says the paired row benefits measured in the
Murrayville trial correlate well with previous research work on the benefits of
higher seedbed utilisation (SBU), which is the proportion of the row spacing
occupied by the crop. SBU can be increased either by reducing row spacing or
increasing lateral seed spread on each row, such as with paired-row and
spreader boot systems.
“Paired row and spreader boot systems allow higher SBU with
the same row spacing, which improves grain yield potential, reduces fertiliser
toxicity risks and enhances crop competition with weeds,” he said.
According to Dr Desbiolles, however, this does not mean that
paired row systems are always an obvious solution.
“These systems have potential disadvantages, such as reduced
seed outlet size which may not be suited to larger seeds or high seed rates,
higher risk of blockages in sticky conditions and higher soil disturbance with a
potential increased risk of pre-emergence herbicide damage, depending on the
design,” he said.
Sandy soil systems
“Sandy soils present the highest risk of the soil drying out
quickly and reducing germination,” Dr Desbiolles said.
Recent research work suggests the following strategies should
be considered for more reliable crop establishment in sandy soils, where
marginal moisture conditions are encountered:
Place seed in contact with undisturbed soil
moisture. This requires side banding or paired row banding able to place seeds
on undisturbed ledges, or single shoot systems able to band seeds at furrow
tilling depth. Deep furrow sowing
capabilities may be required to reach moisture, or else growers can use low
rake angle openers, low speed and compact seed banding systems to delve deeper.
Minimise the fertiliser applied with seeds to
control fertiliser toxicity, and use a double shoot system, with side or side plus
It is important to note that a lack of sub-seed disturbance
may increase the severity of rhizoctonia damage on young seedlings, and the use
of liquid banding technology to combine in-furrow trace element application and
fungicide protection at sowing may be necessary as part of a mitigating strategy.
Seed-fertiliser separation is particularly important in
small seeded crops like canola for successful germination on sandy soils.
“Obtaining high SBU is important to manage fertiliser
toxicity risks,” Dr Desbiolles said. “In marginal moisture conditions,
including non-wetting soils, it may be necessary to have full separation
between seed and basal fertiliser, preferably banded at depth to maintain the
maximum crop establishment potential.”
Trials in the SA Mallee in the early 2000s found that 70 per
cent SBU tyne sowing was able to significantly minimise establishment losses in
canola, reporting no grain yield loss at harvest, compared to up to 45 per cent
yield loss to fertiliser toxicity at 15-20 per cent SBU.
Successful use of high SBU systems requires careful
selection of equipment to suit growers’ conditions.
“When selecting for a higher SBU system, there are many
factors to consider including single or double shoot, distinct split-rows or a
wide band sowing, integrated opener design or wing attachment for an existing
opener, and fertiliser placement relative to the seed zone,” Dr Desbiolles
“In order to better establish crops in marginal soil
moisture, it is important to select a design able to place seeds on undisturbed
soil moisture, being aware that some systems will instead place seeds into
furrow backfill, at greater risk of diluted moisture and potentially pre-emergent
Non-wetting soil challenges
Non-wetting sands present specific challenges leading to
slow and patchy seedling emergence. Trials in non-wetting sand at Moorlands in South
Australia in 2015 found that crop establishment under a single-shoot narrow
point system significantly reduced due to fertiliser toxicity, from 82 per cent
emergence to 58 per cent (in a system with 25cm row spacing and fertiliser
rates of 13 kg/ha nitrogen, 9kg/ha phosphorus and 12 kg/ha sulphur). Crop
emergence rate was further reduced down to 34 per cent with a low soil disturbance,
single disc system, due to the combined effect of fertiliser toxicity and lack
of surface soil clearing.
“The best treatment, reaching over 90 percent emergence, in
the Moorlands trial was obtained by adding a shallow operating scooping share
ahead of a triple disc seeding system to clear away the top 3-4cm of soil into
the inter-row zone and assist with placing seeds into moist soil,” Dr
“This scoop design used as a proof-of-concept required low
operating speed (5km/h) to avoid ridging.
Paddock-ready ‘scoop’ solutions would need testing but could include
concepts based on modified front coulters or knife points to emphasise an
effective surface soil clearing at common operating speeds.”
“Such targeted furrow disturbance is a useful concept to
apply in non-wetting sands and may also more generally be useful in dry sandy
soil conditions when seeking to place seeds into moisture and controlling
On and near row sowing in
non-wetting sand can promote access to greater moisture available in existing
This approach was successfully
demonstrated in recent Western Australian research and also validated in the SA
Mallee during 2015. CSIRO trials in 2015 also showed a significant reduction in
brome grass germination associated with this technique.
Successful near-row sowing is more
challenging to achieve than inter-row sowing, and requires a side banding
seeding system and RTK tractor plus implement auto steer. Inter-row sowing should, however, be used
where soils are evenly wetted and moisture is not limiting, to access other
Managing herbicide toxicity
Tyne seeders are reliably safest at ensuring crop safety, as
long as the following guidelines are adhered to:
Control speed to ensure no soil throw reaches
adjacent furrows and the majority of herbicide is concentrated over the
Ensure seeds are placed at sufficient depth with
clean backfill to achieve adequate physical separation between crop seed and
herbicide (known as ‘positional selectivity’).
Create stable furrows to limit the risk of
contaminated soils backfilling over time, and leaching of soluble herbicides
into the seed zone.
Care must be taken with disc seeders when using pre-emergent
herbicides. Trials at Roseworthy in the SA lower-north in 2012/13 showed that
trifluralin significantly reduced wheat emergence with single discs, by up to 50
per cent. However, using triple discs or applying Sakura® caused no damage.
The greater safety with triple disc systems is explained by their
soil throw features being akin to a knife point system. Further, the inclusion of residue managers
fitted ahead of the single disc openers significantly reduced crop damage. Growers should always follow herbicide labels
to assess suitability for disc seeders.
08 8302 3946,
Useful Seeding Resources
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