DOI: 10.1002/ppp3.70235 ISSN: 2572-2611

Plant species are more important to bacterial community composition than seeding ratio in a pea‐canola intercropping system

Janice M. Parks, Braeden J. Stiffler, Maren L. Friesen
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Societal Impact Statement

Demand for agricultural land has increased due to rising demand for food, potentially leading to expansion into previously untouched habitats, which threatens refugia of native plants. We aimed to provide insight into how variation in seeding ratio may impact soil bacterial communities in a pea‐canola intercropping system, potentially altering crop efficiency. We found a high level of variation in bacterial communities across seeding ratios, demonstrating that changes to aboveground diversity can unpredictably impact belowground communities. Information on how management practices impact bacterial communities may be used by agronomists to design efficient intercropping systems, reducing the need for agricultural expansion.

Summary

The pea‐canola ( Pisum sativum – Brassica napus ) intercropping system (peaola) is a high yielding mixed intercropping system that is being studied to improve agricultural sustainability and productivity. Plant‐microbe interactions have been considered important to intercrop success, but it is unknown how these dynamics change based on crop seeding ratios. The goal of this study was to determine how seeding ratio and cropping system impact the diversity, structure, and predicted function of the bacterial community in peaola. We also determined how nitrogen availability in soil and pea and canola leaf nitrogen content were impacted across seeding ratios and cropping systems.

We collected soil, rhizosphere, and mature leaf samples from peaola, with nine different seeding ratios, and monoculture pea and canola controls. Bacterial communities in soil and rhizosphere were characterized using 16S rRNA, and soil and leaf nitrogen content were measured.

Intercropping increased the nitrogen content of mature canola leaves, suggesting changes to nitrogen availability. Plant influence on the bacterial community was determined to be the primary contributor to community structure and function. Overall, no clear patterns were observed between seeding ratios and the bacterial communities.

High variability in our results highlights that changes to aboveground diversity may have unpredictable impacts on belowground diversity, making it difficult to make management decisions. Our observations may also be due to additional factors beyond the ratio of pea:canola planted, or a result of sampling variation.

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