Poor Wheat Growth Following Canola

Dr John Kirkegaard (Principal Research Scientist) - CSIRO Plant Industry

Type: Research Paper
Knowledge level: Advanced

Farm Table says:

Identifying why this occurs is important to ensure that the expected benefits from canola break crops are realised and canola can retain its important role in the crop sequence.


Causes, consequences and control

What is the problem?

  • There have been increasing anecdotal reports of instances where wheat crops perform poorly following canola, although the exact cause/s remain unclear.

What did the research involve?

  • growers should retain canola in the rotation as the expected average benefits to following wheat yields are in the order of 20%
  • there is no evidence in SE Australia that poor wheat growth following canola is related to lower levels of mycorrhizae or to any other negative impacts on soil biota. In the northern wheat belt, reports of poor growth of wheat after canola associated with lower mycorrhizae appear to be restricted to poorly fertilized crops and/or unusually dry seasons
  • as crop yields increase, cropping phases lengthen, and canola and other brassica crops (particularly herbicide-tolerant) increase in frequency, the removal of soil nutrients from our agricultural systems will greatly increase

What were the key findings?

  • the major economic benefit from this project will arise from continued and possibly increased use of canola break crops in dryland cropping, and reduction in yield loss associated with the manageable causes of poor crop performance
  • allowing wheat crops following canola to meet their yield potential will benefit the environment through ensuring efficient use of inputs, especially fertilizers, and allow these disease-free crops to develop deep root systems capable of extracting nutrients and water from depth in the soil


Final comment

“ Indifference, low mycorrhizal colonization may reduce the growth of crops in warmer northern regions, but the adequate addition of nutrients should avoid this problem except in drought years where dry soils reduce nutrient availability.’’

Several issues worthy of further investigation were revealed in this study – please see full document.

2003 - Australia - Dr John Kirkegaard (Principal Research Scientist) - CSIRO Plant Industry
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