Sowing rates for
different canolas
Brooke White (BCG)
Take home messages
• Target hybrid canola sowing rates that will produce no less than 20 and no
more than 40plants/m2.
• Hybrid canola offers improved characteristics over open pollinated (OP)
varieties but seed costs roughly twice that of OP varieties and hybrid seed
cannot be retained from year to year.
Background
Seed from hybrid canola varieties is larger than open pollinated (OP) varieties but has greater
early vigour. Non triazine tolerant hybrids also have an average 14% higher establishment rate
compared with OP varieties.
In other crop types, larger seeded varieties are sown at a higher rate to compensate for the fewer
seeds per hectare, but as hybrid canola has such high early vigour and biomass production, it is
thought that sowing these varieties at the same or lower rates than OP varieties will not cause
yield loss.
Unlike OP varieties, hybrid canola seed must be purchased each season and cannot be retained
from year to year. Hybrid canola seed costs around $23/kg - more than double that of OP
varieties. Also, because of the larger seed size, each bag of hybrid canola seed contains 25 to
50% less seeds than an OP variety.
Canola is already an expensive crop to grow, so any reduction in costs would be welcomed by
growers.
Growers who have used low sowing rates (3kg/ha or less) for both OP varieties and hybrids
in the past have taken steps to prevent insect damage. Any loss of seedlings can have major
consequences and reduce plant numbers below the optimum.
Optimal plant density for hybrids may be lower than for OP varieties due to greater early
vigour and biomass production as well as the high cost of hybrid seed.
Low plant density (below 20 plants/m2) can reduce hybrid canola yield but research to date
has not shown an economic benefit in increasing sowing rate above 40 plants/m2 in the low to
medium rainfall zone.
Aim
To investigate the effect of sowing rate on yield of hybrid canola varieties compared with open
pollinated varieties.
BCG 2010 Season Research Results 56
Method
A replicated trial was established at Culgoa in the southern Mallee, where both farmer-retained
and newly purchased 44C79 seed was sown at 3kg/ha and the hybrid variety 44Y84 was sown
at 1, 2 and 3kg/ha (Table 1).
Location:Culgoa
Replicates:4
Sowing date:
23 April 2010
Seeding density:
sown at 1-3kg/ha
Crop type/s:
44C79, 44Y84
Fertiliser:
50kg/ha MAP at sowing; 90kg/ha urea during cabbage stage.
Seeding equipment: Gason parallelogram knife point, press wheel (30cm spacing).
Table 1. Canola varieties and sowing rates trialled, Culgoa.
Variety
Seed type
Sowing rate (kg/ha)
44C79 - farmer retained
Open pollinated
3
44C79 – purchased
Open pollinated
3
44Y84
Hybrid3
44Y84
Hybrid2
44Y84
Hybrid1
Results
Establishment
The hybrid 44Y84 sown at 1 and 2kg/ha had the lowest establishment with 22 and 29 plants/m2
respectively (Figure 1). The farmer-retained 44C79 sown at 3kg/ha also had low establishment
with 34 plants/m2, half that of the certified 44C79 seed.
No treatments fell below the 20 plants/m2 benchmark, but the certified 44C79 and 44Y84
sown at 3kg/ha produced more than 40 plants/m2, with 69 and 56 plants/m2 respectively.
When the Greenseeker® (a handheld device that measures ‘greenness’) was used to measure
early groundcover at the 4-5 leaf stage, the two treatments with the most plants/m2 (certified
44C79 and 44Y84 sown at 3kg/ha) had the most groundcover.
Lower sowing rates reduced groundcover for the hybrid.
The farmer-retained 44C79 treatment had the lowest groundcover of all treatments.
BCG 2010 Season Research Results 57
Figure 1. Establishment of canola (plants/m2) and groundcover (measured
as NDVI using Greenseeker), at the 4-5 leaf stage, Warne.
Treatments marked with the same letter are not signifcantly different from one
another for establishment (LSD 21.19, p<0.05). NDVI LSD 0.062, p<0.05.
Yield and quality
At 3kg/ha sowing rate, the hybrid 44Y84 was higher yielding than 44C79, despite earlier
measurements showing that the certified 44C79 had equivalent groundcover to the hybrid at
the 4-5 leaf stage (Table 2).
The 2 and 3kg/ha sowing rates produced the highest yields from 44Y84. The 2kg/ha sowing
rate outyielded the 1kg/ha by 0.35t/ha.
The farmer-retained 44C79 seed yielded the same as the newly purchased, certified seed,
despite lower establishment and lack of vigour at the 4-5 leaf stage.
Quality was excellent, with all varieties producing above 48% oil.
Table 2. Yield and quality of canola varieties at different sowing rates, Warne. Yield
results followed by the same letter are not significantly different.
Variety
Sowing rate (kg/ha)
Yield (t/ha)
Oil (%)
44C79 farmer retained
3
2.13c
49.30
44C79 purchased
3
2.02c
48.42
44Y84
3
2.45ab48.45
44Y84
2
2.70a48.20
44Y84
1
2.35b48.75
LSD (p<0.05)
0.33
CV%
9.21.6
BCG 2010 Season Research Results 58
NS
Interpretation
Sowing the hybrid 44Y84 at 2kg/ha produced optimal seedling density and yield in this trial.
The extra plants produced from the 3kg/ha sowing rate did not add economically to yield.
This trial showed that the hybrid 44Y84 canola can be successful with an establishment of 29
plants/m2 (2kg/ha in this trial) but yield can decline when establishment is 22 plants/m2 (1kg/
ha in this trial).
With canola worth approx $530/t in 2010, these results show that economically it was
worthwhile spending the extra $23/kg on seed and sowing at 2kg/ha rather than 1kg/ha.
Commercially, sowing at 1kg/ha does not leave much room for error, as plant numbers are
so low from the beginning of the season that any further losses can have yield effects, despite
canola’s ability to compensate for low plant numbers.
Sowing rates should be calculated based on optimal plant density rather than a set rate. This is
because hybrids vary considerably in seed size and even between seed lots. Seed size information
is provided with each bag of seed. When calculating sowing rates, a good rule of thumb for
non triazine tolerant hybrids is 75% establishment. However, this can be as high as 90% when
sowing conditions are ideal, or as low as 25% when poor. For OP varieties, a good rule of
thumb is 60% establishment.
Sowing rates below 2kg/ha must also be accompanied by vigilant insect management and
monitoring to ensure that already low plant numbers are not further reduced through insect
attack.
These findings support previous work conducted by the GRDC and Australian Oilseeds
Federation through the Better Oilseeds project, which could not show an economic benefit to
yield with hybrid seedling densities above 40 plants/m2 in the low and medium rainfall zones.
The high cost of hybrid seed generally does not compensate for any increases in yield in these
regions.
Acknowledgments
This trial was funded by BCG members, through their membership fees.
BCG 2010 Season Research Results 59