Background
The canola industry in Western Australia is expanding in low rainfall areas. Primarily, growers choose open pollinated TT varieties. However 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 approximately 25 times more expensive than the seed of open pollinated canola. Inevitably if growers are forced into hybrids they may wish to minimise seed costs by sowing at low densities.
Aim
To investigate the plant density response to yield and oil content of TT and RR hybrid canola in comparison with open-pollinated canola.
Trial details
| Property | Great Southern Agricultural Research Institute, Katanning, paddock 1 |
|---|---|
| Agzone 3 | Growing season rainfall (GSR) = 353mm |
| Soil type | Loam (3.4% organic carbon) |
| Paddock rotation | 2012 oats, 2011 lupins, 2010 oaten hay, 2009 canola |
| Sowing date | 21 May 2013 |
| Fertiliser (kg/ha) | 100 Agstar (14.3% N, 14.0% P, 9.6%, 0.6% Zn )drilled below the seed 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 |
Treatment detail
32 treatments:
- Two herbicide tolerant systems: Triazine Tolerant (TT) and Roundup Ready (RR) canola
- Four cultivars:
TT = Open pollinated - ATR Stingray; and Hybrid - Hyola 450TT
RR = Open pollinated - GT Viper; and Hybrid - Hyola 404RR
- Eight densities: 5, 10, 15, 20, 30, 40, 60, 80 plants per metre squared (plants/m2)
- Trial design: split plot design, with herbicide tolerance (HT) as main plots and cultivars x eight plant density as sub plots
Replications: three
Assumptions used in gross margins
- Oil bonus: +/- 1.5% per unit of oil (%) either side of 42%, with no oil ceiling
- Additional costs: seeding, harvest, insecticides assumed to be $100/ha
- Nitrogen costs: $1/kg, application costs $8/ha per application
- RR costs: seed $31/kg, herbicides $28/ha
- RR price: grain worth $479/t (CBH Pool Albany 5 Nov 2013)
- TT costs: seed $2/kg, herbicides $47/ha
- TT price: grain worth $502/t (CBH Pool Albany 5 Nov 2013)