Canola frequency effects on nutrient turnover and root-microbe interactions
Date: September 2021
Term: 3 years
Status: Completed
Researchers: Tim Dumonceaux, Jennifer Town and Breanne Tidemann, Agriculture and Agri-Food Canada; Bobbi Helgason, Melissa Arcand and Steven Siciliano, University of Saskatchewan
SaskCanola Investment: $129,467
Total Project Cost: $258,936
Funding Partners: Alberta Canola Producers Commission
Grower Benefits
Crop rotation is an important component to sustainable, healthy agroecosystems aiding in disease suppression, nutrient cycling and risk mitigation. In this study, researchers examined the agronomic impacts of crop rotation strategies including canola-canola; canola-wheat; and canola-pea-barley. It was found that long-term, short-rotation canola had transient, site-dependent effects on soil nutrient availability. In addition, crop rotation strategy had a stronger impact on the fungal microbiota at all sites, years and soil compartments examined compared to the bacterial communities.
Project Summary
Crop rotation is an important strategy used by producers to maximize soil and plant health. Rotation strategies are complex and involve a variety of biological, economic and social factors that determine the yearly sequence of crops that are planted. The effects of common rotation strategies on the microbial communities recruited by the plant have not been investigated. Researchers found that the soil and root-associated fungal microbiome responded more strongly to crop rotation compared to the bacterial communities, and identified a fungus, Olpidium brassicae, that was particularly dominant in the canola-only rotations. These findings highlight the importance of considering the effects of crop rotation on the whole plant, including its associated microbial partners, and point to new areas for future research.
The objectives of this research included determining the effect of crop rotation on the nutrient fluxes experienced by canola roots during flowering; examining the organic acids produced by canola that shape the composition of the root-associated microbial communities, and characterizing the resulting microbial communities. We aimed to determine the effect of crop rotation on the whole plant, including its microbial partners, providing producers with holistic data on the biological effects of production choices that are informed by a combination of economic, biological and pragmatic considerations.
This project leveraged the efforts of a long-established crop rotation study that examined the agronomic impacts of crop rotation strategies including canola-only; canola-wheat; and canola-pea-barley. Soil samples were examined from three locations (Scott, SK; Swift Current, SK; Lacombe, AB) representing a variety of soil types (brown; dark brown; black), and the samples were taken during the canola year of well-established rotations of the larger study. Commercially available Plant Root Simulator® probes from WesternAg were used to examine the flux of nutrients available to canola roots, and ion exchange chromatography to examine the organic acids produced by the canola plants. Bacterial and fungal communities were characterized using DNA sequencing of the soil, rhizosphere and roots. In this way, we examined the long-term impact of crop rotation on soil processes and the canola microbiome to better understand how canola cropping frequency impacts crop performance.
Researchers found that long-term, short-rotation canola had transient, site-dependent effects on soil nutrient availability. This was likely due to the use of soil test-based fertilization according to normal agronomic practices, which provided a crop responsive prescription for fertilizer addition and ultimately, adequate nutrients for crop growth. In addition, we determined that the crop rotation strategy had a stronger impact on the fungal microbiota at all sites, years, and soil compartments examined compared to the bacterial communities. Crop rotation affected the abundance of fungi associated with both detrimental and beneficial effects on crop production, and this effect was most pronounced in and near canola roots. In particular, continuous canola resulted in a predominance of a fungus identified as Olpidium brassica, a poorly understood root colonizer with a life cycle that is similar to that of the clubroot pathogen, Plasmodiophora brassicae. This provides a direction for future studies.
These findings highlight the importance of considering the impacts of crop rotation strategies on the microbiota associated with canola roots, and demonstrate that the fungal biome is more affected by continuous canola than the bacterial community. Continuous canola resulted in the dominance of a particular fungus, Olpidium brassicae, with presently unknown effects on canola health and resiliency.
Full Report PDF: Canola frequency effects on nutrient turnover and root-microbe interactions
Other References to this Research Project
Canola Research Hub Blog: Impacts of continuous canola on root microbes
Canola Watch Podcast: Plants, microbes and new tools (January 28, 2022)
Canola Week Video Presentation: Canola Frequency Effects on Nutrient Turnover & Root-Microbe Interactions (2021)