Canola response to plant density at Pingrup 2013 trial report

Summary

In this 2013 trial:

• Roundup Ready varieties GT Viper and Hyola 404 Roundup Ready (RR) and open pollinated hybrid Hyola 450 Triazine Tolerant (TT) had lower economic optimum plant densities than open pollinated TT ATR Stingray.
• Both RR and TT groups provided an effective weed management in this trial.

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. Growers deciding to plant hybrid varieties 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: Craiglinne Estate, Pingrup - Paul Hicks.
• Agzone 5: Growing season rainfall (GSR) = 315 millimeters (mm).
• Soil type: Clay loam (1.98% organic carbon).
• Paddock rotation: 2012 - barley, 2011 - oats.
• Sowing date: 20 May 2013.
• Fertiliser - kilogram per hectare (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/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 November 2013).
• TT costs: Seed $2/kg, herbicides $47/ha.
• TT price: Grain worth $502/t (CBH Pool Albany 5 November 2013).

Results

Established plant density

The established plant densities were nearly 47% of the targeted plant densities. Hyola 450TT established significantly (p<0.05) higher plant numbers than GT Viper at higher seeding rates (Figure 1).

Grain yield and gross margins

All varieties responded to increasing plant density. However, the response started to flatten at about 15 plants/m² for Roundup Ready GT Viper and Hyola 404RR varieties and at about 30 plants/m² for open-pollinated ATR Stingray and Hyola 450TT varieties (Figure 2). The economic optimum plant density for both Roundup Ready GT Viper and Hyola 404RR was 19 plants/m² and for the Triazine Tolerant ATR Stingray and Hyola 450TT it was 52 and 24 plants/m², respectively. Hyola 404RR was the highset yielding variety (1624kg/ha) but ATR Stingray produced highest gross margins of $574/ha. Averaged over the densities, the gross margins of other varieties ranged from $470-$555/ha.

Figure 1 Observed plant density of canola varieties against target plant density at Pingrup in 2013.

Figure 1 Grain yields of open-pollinated and hybrid canola varieties.

Figure 3 Gross margins of open-pollinated and hybrid canola varieties.

Conclusion

Roundup Ready varieties GT Viper and Hyola 404RR and Triazine Tolerant hybrid Hyola 450TT had lower economic optimum plant densities (19-24 plants/m²) than ATR Stingray (52 plants/m² ). Although Hyola 404RR was highest yielding, ATR Stingray produced the highest gross margins. In this trial weeds were effectively managed in both RR and TT groups.

Acknowledgements

This trial (13GS19) is one of a series conducted throughout WA as part of the GRDC/DPIRD co-funded project 'Tactical break crop agronomy'. Thanks to Paul Hicks for hosting the trial and to the Katanning Research Support Unit for trial management.