Linking Soil Nitrogen Cycling and Plant Biotic Traits to Nitrogen Use Efficiency Parameters Among Diverse Canola (Brassica napus) Genotypes
Date
2023-07-06
Authors
Journal Title
Journal ISSN
Volume Title
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ORCID
0000-0003-1333-4117
Type
Thesis
Degree Level
Doctoral
Abstract
Canola (Brassica napus) is a dominant oilseed crop grown globally, second only to soybean. It requires relatively large amounts of nitrogen (N) fertilizer input compared to other oilseeds or cereal crops, but global estimates suggest that less than 50% of applied nitrogen (N) is recovered in canola seed harvest, indicating significant N-use inefficiencies. These inefficiencies contribute to resource overuse and waste, that can negatively impact the environment. There is significant variation in N-use efficiency (NUE) between crop genotypes, across different soil types and regions, and between different crop management systems. These factors make it challenging to implement strategies to improve NUE. Therefore, to create strategies to improve NUE, researchers must examine genotype (G) x environment (E) x crop management practices (M). Three studies employing varying combinations and degrees of G x E x M highlighted below-ground interactions (between soil properties, root phenology, and rhizosphere and root endosphere microbiomes) and above-ground plant traits (N uptake, N utilization, N partitioning, and seed protein) to determine relevant factors that contribute to canola productivity. This dissertation aims to link below-ground soil–plant–bacterial interactions to plant N uptake, remobilization, and partitioning that can improve canola harvest parameters such as yield, partial factor productivity (PFP), and NUE. Sixteen canola genotypes were grown on a Dark Brown Chernozem in Saskatchewan, Canada, with soil and plants sampled five times from 32-81 days after sowing (DAS), and seeds sampled at 81 DAS. Canola genotypes in this thesis exhibited different concentrations of below-ground soil parameters like moisture and NO3- -N; and genotypes with higher NUE and PFP were linked greater absorption of these soil parameters. Root morphology and rhizosphere and root microbiomes did not correlate with NUE or PFP. However, root surface area negatively correlated with soil NO3--N concentrations, suggesting that genotypes with larger absorptive surfaces acquired more soil mineral N. Rhizosphere bacterial diversity and community structure varied with changes in soil NH4+-N and pH, respectively, while root bacterial diversity and community structure varied with changes soil moisture and pH, and soil NO3--N, respectively. Plant-bacterial interactions likely shaped these microbiomes, making them distinct between genotypes.
Description
Keywords
canola, Brassica napus, genotypes, nitrogen use efficiency, nitrogen availability, nitrogen mineralization, potential nitrification, fertilizer rates, growth stage, root endophytic bacteria, rhizosphere bacteria, root architecture
Citation
Degree
Doctor of Philosophy (Ph.D.)
Department
Soil Science
Program
Soil Science