Dual-purpose Cropping in the High Rainfall Zone
- Winter or long-season spring canola can be sown early, grazed during mid-winter and produce high grain yield with high oil content in summer
- Canola provides an excellent break crop for winter cereals, increasing overall profitability and improve flexibility in mixed farming operations
Since 2004, Dr John Kirkegaard has been assessing the potential of different canola varieties as dual-purpose crops. As with wheat, the timing of the grazing is crucial to ensure maximum yield, however, mineral supplements are not necessary for the animals. Grazing time can also influence to a certain extent when the plants will flower. Farmers can use this to their advantage to ensure flowering occurs well after the risk of any frost has passed.
Growers should sow early (late March to mid-April) with a long-season canola. Prepare well and use press wheels in dry conditions to ensure good seed to soil contact.
- Use canola varieties with strong early vigour and good blackleg resistance, as grazing usually increases both the severity and prevalence of blackleg.
- Aim for good plant densities of around 50 plants/m2 to ensure that plants establish quickly. Nitrogen fertiliser can either be added early on or delayed until after grazing – do not apply N fertiliser just before or during grazing.
- Growers will need to have good stock levels to capitalise on the opportunity that grazing canola presents. This may entail purchasing additional stock which then requires additional capital outlay.
- Timing of stock removal is the most important decision growers will make during the season. Stock must be removed before the canola elongates to 10cm above ground level to prevent yield penalties.
- CSIRO research suggests that dual-purpose canola can deliver a marginal gross profit increase of $100-$400/ha more than growing grain canola only.
- The reduced bulk of grazed canola can make windrowing easier at grain harvest during high-yielding years and this improves the rate if windrowing and subsequent harvesting. Canola can also provide an excellent break crop between dual purpose wheat and reduce the threat of WSMV considerably.
There are risks associated with mixed cropping systems. Growers need to prepare paddocks well in advance of sowing to reap the rewards from dual purpose cropping systems. Growers need to ensure proper weed control, soil moisture, stubble loads and other factors that may have an impact on the successful establishment of young plants. Canola varieties need to be vigorous and highly resistant to blackleg. Also crops need to be sown early in order to be able to capture the benefits of grazing first.
Sprague SJ, Kirkegaard JA, Marcroft SJ, Graham JM. 2010. Defoliation of Brassica napus increases severity of blackleg caused by Leptosphaeria maculans: implications for dual-purpose cropping. Annals of Applied Biology. 157: 71-80.
Kirkegaard JA, Sprague SJ, Dove H, Potter T, Marcroft S, Kelman W, Lilley J. 2010. Adaptation of winter canola (Brassica napus) for grain and dual-purpose use in Australia’s high rainfall zone. Proceedings 15th Australian Agronomy Conference, 21-25 November, Lincoln NZ. www.agronomy.org.au
Kirkegaard J, Sprague S, Dove H, Kelman W, Hamblin P. 2010. Best-bet management for dual-purpose canola. Invited contribution in GRDC-sponsored Grains Research Technical Update, Wellington, NSW, ed. J. Cameron (Independent Consultants Australia Network, Hornsby NSW). Pp. 58-61.