Canola works well in canola-wheat-corn-soybean rotation

Key result: This Eastern Canada study tested canola in typical Eastern Canada crop rotation systems and found that canola performed well after soybeans and wheat produced its best yields following canola.

Project title, Principal investigator: “Canola Rotation Studies,” Claude Caldwell, Dalhousie University

Funding: Growing Forward 2

Crop rotation is recognized as one of the best management practices in field crop production, whether canola or any other crop. The purpose of this study was to gain a better understanding of how canola can fit into existing cropping systems in Eastern Canada. Researchers wanted to calculate the economic benefit of growing canola as well as nutrient utilization efficiency and carbon footprints in different cropping systems through the collection of soil, crop growth, yield and tissue N concentration data, to investigate major diseases and insects of canola production in different cropping systems, and to identify and establish a sustainable cropping system for canola production in Eastern Canada.

A four-year phase rotation (canola-wheat-corn-soybean) experiment with 13 crop sequence combinations and four replications per site was established in Ottawa, Ont., Ste. Anne de Bellevue, Que. and Canning, N. S.

The following conclusions are drawn from data analysis:

  1. In most cases, the canola following soybean rotation produced the best yields of all the canola rotations.
  2. In most cases continuous canola plots (CC) produced the worst yields of all the canola rotations. Clubroot became an issue at one site but only in the continuous canola rotation.
  3. There appears to be a slight yield advantage of planting wheat after canola. In four out of the five years, the rotational wheat after canola produced the best yields of all three rotations.
  4. The different crop rotations had no significant effect on canola seed oil concentration.
  5. Root:shoot ratio can be a good assessment of the health of a crop. Continuous canola plots that had the poorest yields also had the lowest root:shoot ratios, compared to the other canola rotations. However, even though the canola following soybean plots had the highest yields, they did not necessarily have the highest root:shoot ratios. There does not seem to be a correlation between root:shoot ratios and the final yields of the wheat rotations. Wheat plots following canola had the highest yields, but not the highest root:shoot ratios.
  6. This rotational effect may likely be associated with the change in soil microbial communities, which indirectly affected the availability of soil nutrient supply, and thereby the uptake of plant nutrients and nutrient balance. This requires further investigation.
  7. More research is also required to understand soil and root dynamics.

Baoluo Ma, Agriculture and Agri-Food Canada (AAFC) research scientist and co-investigator for this project, was invited to contribute a review paper titled “Crop rotation: A sustainable system for maize production” in a publication called “Achieving Sustainable Maize Cultivation”, published by Burleigh Dodds Science Publishing Ltd., Swanston, Cambridge, U.K. The paper included this observation: “The yield ratio (rotational canola yield as a fraction of the average monoculture canola yield) was also affected by the previous two-year sequence of crops, with canola yield increase by two to 65 per cent when following the maize-soybean sequence, compared to monoculture canola.”

Further analysis of the multi-year data is ongoing, and the large dataset generated will provide additional insights into the rotation effect.