Abstract: Efforts to reduce the use of nitrogen fertilizers have been increasing due to their environmental consequences on soil and ecosystem health. Legume–non-legume intercropping systems have been proven as a method to reduce the use of nitrogen fertilizers while maintaining yields. The pea–canola (Pisum sativum–Brassica napus) intercropping system (peaola) has shown promise, as its highest yields occur with minimal to no nitrogen fertilizer application. Therefore, the goal of our study was to determine how nitrogen fertilization impacts the bacterial community and its predicted function in peaola to aid in agricultural sustainability initiatives. To accomplish this goal, we investigated (i) how the bacterial community was altered in composition and predicted function under three different nitrogen fertilizer application rates (0, 33, and 67 kg N ha−1) in the soil and rhizosphere and (ii) how the concentration of nitrogen was impacted in peaola across different fertilizer application rates. Overall, we found that plant species was the primary factor responsible for differences in the diversity, structure, and predicted function of the rhizosphere bacterial community, demonstrating the ability of plants to control their rhizosphere community composition. In bulk soil, we did not observe differences between cropping systems for the bacterial communities, but fertilizer treatment alone did cause shifts in the community diversity. No significant differences were found in the concentrations of nitrate, nitrite, and ammonia in peaola across fertilizer treatments. This suggests that the changes observed within the bacterial community could reflect shifting plant nutritional needs, leading to plants receiving the necessary levels of nitrogen to thrive. [Figure: see text] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.
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