Canola response to plant density at Holt Rock 2013 trial report

Summary

In this 2013 trial:

• The grain yield of canola varieties started to plateau at approximately 20 plants per square metre (plants/m²).
• Hyola 404RR had the flattest yield response meaning that its yields were less affected by lower plant densities.
• Hyola 404RR was the highset yielding variety and also produced highest gross margins.
• Open-pollinated variety treatments were weedier than hybrids especially at lower densities.

Background

The canola industry in Western Australia is expanding in low rainfall areas. Primarily, growers choose open-pollinated Triazine Tolerant (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.

Aim

To investigate the plant density response to yield and oil content of Triazine Tolerant (TT) and Roundup Ready (RR) hybrid canola in comparison with open-pollinated canola.

Trial details

• Property: Hy-Yakka, Holt Rock - Brent and Clare Hyde.
• Agzone 5: Growing season rainfall (GSR) = 256 millimetres (mm).
• Soil type: Loam (1.17% organic carbon).
• Paddock rotation: 2012- barley, 2011 - barley, 2010 - wheat, 2009 - lupins.
• Sowing date: 16 May 2013.
• Fertiliser (kg/ha): 100 Agstar (14.3% N, 14.0% P, 9.6%, 0.6% Zn ) drilled below the seed at seeding, 120 kilogram per hectare (kg/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 - CB Telfer; 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 and no significant difference (p>0.05) between varieties were observed (Figure 1).

Grain yield and gross margins

All varieties responded to increasing plant density but started to plateau at approximately 20 plants/m² (Figure 2). Hyola 404RR had the flattest yield response meaning that its yields were less affected by lower plant densities. The economic optimum plant densities were 31, 40, 46 and 21 plants/m² for GT Viper, Hyola 404RR, CB Telfer and Hyola 450TT, respectively. Roundup Ready Hyola 404RR was the highset yielding variety (2054kg/ha) and also produced highest gross margins of $752/ha. Averaged over the densities, the gross margins of other varieties ranged from $505-$695/ha.

Rye grass

There was much less ryegrass in Hybrid treatments than open pollinated varieties especially at low plant densities. Ryegrass head numbers decreased rapidly as the crop density increased (Figure 3).

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

Figure 2 Grain yields of open-pollinated and hybrid canola varieties.

Figure 1 Ryegrass head numbers in open-pollinated and hybrid canola varieties.

Figure 4 Gross margins of open-pollinated and hybrid canola varieties.

Conclusion

All varieties responded to increasing density but started to plateau at approximately 20 plants/m². Hyola 404RR had the flattest yield response meaning that its yields were less affected by lower plant densities. Hyola 404RR was the highest yielding variety and also produced highest gross margins. Ryegrass numbers were high at lower plant densities especially in open-pollinated varieties.

Acknowledgements

This trial (13GS20) is one of a series conducted throughout WA as part of the GRDC/DPIRD co-funded project 'Tactical break crop agronomy'.Thanks to Brent Hyde for hosting the trial and to the Katanning Research Support Unit for trial management.