Western Australia
April 14, 2015

By GRDC western regional panel member Gemma Walker

Research is helping to identify and develop canola varieties and management tactics to maximise yields across the Western Australian grainbelt.

Recent findings include confirmation that delaying top-up nitrogen (N) applications until canola crops are flowering is unlikely to incur big yield or oil production penalties in lower rainfall areas.

This is the message from Department of Agriculture and Food (DAFWA) researcher Mark Seymour, who is investigating canola nitrogen timing as part of the GRDC-DAFWA project ‘Tactical break crop agronomy in WA’.

Mr Seymour says lower rainfall environments can be unkind to canola and profits are not always assured.

But in these areas, crops sown in mid to late-April will flower in mid-July, allowing enough growing season time to delay top-up N decisions until performance and likely yield potential can be assessed.

Trials investigating canola nitrogen timing were conducted in 2013 and 2014 at nine eastern grainbelt sites, from Eradu to Salmon Gums.

According to Mr Seymour, at most sites over the two years, delaying N application until eight or 12 weeks after sowing (close to flowering time) or splitting applications produced similar yield results to earlier times of N application.

This was the general trend for elite hybrid and open pollinated varieties of triazine tolerant (TT) and Roundup Ready® (RR) herbicide technologies.

At most trial sites, oil percentage was not affected by timing of N application when rates were 25kgN/ha.

But when rates increased to a single application of 50kgN/ha applied close to flowering, oil dropped by 0.6-1 per cent at the driest sites in 2013.

Splitting applications to 25kgN/ha at sowing and 25kgN/ha eight or 12 weeks later had a better effect on oil and yield than applying a single dose of 50kgN/ha near flowering.

But despite the reduced oil production caused by delayed N application at some sites, there was little overall impact of N timing on gross margins at most sites.

Mr Seymour suggests that decision support tools such as Select Your Nitrogen, (SYN), N Broadacre and NuLogic can help estimate the total rate of applied N that is likely to provide the best returns.

Meanwhile, CSIRO researcher Heping Zhang is studying the genetic and environmental effects on canola yields in high and low rainfall areas in WA.

In 2013 and 2014, GRDC-funded CSIRO trials were conducted at low rainfall sites in Merredin and Cunderdin and at a high rainfall site at Kojonup to compare about 20 hybrid and open pollinated (OP), TT, Clearfield®, conventional and RR lines.

Dr Zhang says preliminary research findings indicate that TT and RR canola – with early flowering – are more suited to lower rainfall areas because of the low cost and stable yield in TT canola and high yield potential in hybrid RR.

In high rainfall areas, he says longer-season (mid and mid-late flowering) canola allows the crop to accumulate high biomass and therefore has high yield potential.

Hybrid Clearfield® and hybrid RR systems can produce higher yields than OP canola.

CSIRO research is continuing in 2015 and will further investigate genetic traits associated with yield variations between the herbicide tolerant groups and between varieties within the same herbicide tolerant group.

Useful resources for canola growers include the Canola Variety Guide for WA 2015, available at www.agric.wa.gov.au/canola/canola-varieties-2015 and the GRDC Blackleg Management Guide at www.grdc.com.au/GRDC-FS-BlacklegManagementGuide.
 

Website: http://www.grdc.com.au

Published: April 14, 2015