In this 2013 trial:
- Canola yield responded to increasing plant density to 65 plants per square metre (plants/m2) but there was very little response at densities greater than 20-30 plants/m2
- The response was variable within this trial site, which means that is very likely to be quite variable across different years and locations.
- Roundup Ready (RR) canola enabled much better weed control than triazine tolerant canola on this site.
Breeding companies are favouring the development of hybrids in order to pay for breeding services. Hybrids provide growers with more vigorous seedlings, comparatively better plant establishment and generally higher yields. However growers have to purchase new seed of hybrid varieties every year in order to get these potential yield benefits. Seed for hybrid canola is 25 times more expensive than the seed of open pollinated canola. If growers decide to grow hybrids they may wish to minimise seed costs by sowing at lower densities.
To compare the plant density response of yield and oil content between hybrid and open pollinated (OP) canola in Triazine Tolerant (TT) and RR herbicide tolerance groups.
|Property||DPIRD Wongan Hills research facility|
|Agzone 2||Growing season rainfall (GSR) = 249mm, GSR + stored water (estimate) = 286mm|
|Soil type||Loamy sand (1.01% organic carbon), total mineral nitrogen (N) at seeding 52 kilograms per hectare (kg/ha) to 50 centimetres (cm)|
|Paddock rotation||Wheat 2012, Pasture 2009-2011|
|Sowing date||13 May 2013|
|Fertiliser||100kg/ha of Whitgro Extra at seeding, 120kg/ha of Muriate of Potash and 400kg/ha of gypsum (17% Ca, 14% S) topdressed over whole site four weeks after seeding|
|Treatments||32: 2 herbicide tolerant types (RR and TT) × a hybrid and an OP cultivars within each type (GT Viper and ATR Stingray, OP for RR and TT respectively; and Hyola 404 RR and Hyola 450 TT, hybrid for RR and TT respectively) × 8 target densities (5, 10 ,15, 20, 30, 40, 60, and 80 plants/m2)|
Assumptions used in gross margins
- Oil bonus +/- 1.5% per unit of oil (%) either side of 42%, with no oil ceiling
- Additional costs such as seeding, harvest, insecticides assumed to be $100/ha
- Herbicide costs $28/ha for RR, $47/ha for TT
- RR grain worth $482/t (CBH Pool Kwinana 5 November 2013)
- TT grain worth $495/t (CBH Pool Kwinana 5 November 2013)