Canola in Rotations

Summary

Canola is one of the most profitable crops available to grain growers in southern Australia, offering significant benefits in rotations. While traditionally grown as the first crop after pasture, canola is now used more intensively in rotations, raising concerns about herbicide resistance, disease carryover, and blackleg potential. The crop’s high sulfur, gypsum, and lime requirements also offer benefits for rotational crops and pastures.

Introduction

Canola now occupies 6% of the cropped area in key regions of Australia. It plays an essential role in broadleaf rotations, contributing to increased wheat yields and water use efficiency. Initially grown as the first crop after pasture, canola is now being rotated more frequently, which has led to challenges in pest and disease management. The benefits of canola are highlighted, especially in areas with higher rainfall, where its inclusion leads to better soil health and greater overall farm productivity.

Canola Profitability

The growth of canola plantings since the 1990s is driven by its profitability compared to other break crops. Canola offers high gross margins, particularly in regions with winter rainfall. The comparative gross margin analysis for canola versus wheat in southern Australia shows that although canola yields are typically 55-60% of wheat yields, its profitability is often higher due to better market prices and the reduced capital expenditure required for production.

Rotational Benefits of Canola

Incorporating canola into rotations offers several benefits, including improved wheat yields following canola. Research shows that wheat following canola yields 21% more on average than wheat following other crops. Canola also plays a crucial role in breaking the cycle of cereal diseases, particularly fungal pathogens such as take-all, which are reduced by a break in the crop rotation. This "biofumigation" effect, where decaying canola roots release biocidal compounds, further contributes to its positive impact on subsequent crops.

Future Directions

Future directions in canola rotations focus on improving disease management, particularly with blackleg, and addressing the challenges posed by herbicide resistance. The increasing frequency of canola in rotations calls for research into new management practices to minimize disease pressure, especially blackleg, which could overcome current resistance genes. Additionally, the role of herbicide rotation and management practices will become more critical as canola planting expands.

Further Reading

• Angus, J.F., van Herwaarden, A.F., and Howe, G.N. (1991). "Productivity and break-crop effects of winter-growing oilseeds". Australian Journal of Experimental Agriculture 31, 669-677.
• Kirkegaard, J.A., Gardner, P.A., Angus, J.F., and Koetz, E. (1994). "Effect of Brassica break crops on the growth and yield of wheat". Australian Journal of Agricultural Research 45, 529-545.
• Chan, K.Y., and Heenan, D.P. (1991). "Differences in surface soil aggregation under six different crops". Australian Journal of Experimental Agriculture 31, 683-686.
• Kirkegaard, J.A., Sarwar, M., Wong, P.T.W., and Mead, A. (1998). "Biofumigation by brassicas reduces take-all infection". In 'Agronomy – Growing a Greener Future', D.L. Machalk and J.E. Pratley (Eds). 9th Australian Agronomy Conference, Charles Sturt University, Wagga Wagga, pp. 465-468.
• Mead, J.A. (1992). "Rotations and farming systems - the current situation". In 'Rotations and Farming Systems for Southern and Central NSW'. G.M. Murray and D.P. Heenan (Eds), NSW Agriculture, pp. 5–9.
• Potter, T.D. and Salisbury, P.A. (1993). "The role of triazine resistant canola in Australia". 9th Australian Research Assembly on Brassicas, Wagga Wagga, pp. 87-91.