Nitrogen Use Efficiency in Parent vs. Hybrid Canola under Varying Nitrogen Availabilities

Shanay T Williams,Melissa M Arcand,Sally Vail

doi:10.3390/plants10112364

Shanay T Williams, Melissa M Arcand + Show 1 more

Open Access

https://doi.org/10.3390/plants10112364

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Abstract

Improving nitrogen use efficiency (NUE) is essential for sustainable agriculture, especially in high-N-demanding crops such as canola (Brassica napus). While advancements in above-ground agronomic practices have improved NUE, research on soil and below-ground processes are limited. Plant NUE—and its components, N uptake efficiency (NUpE), and N utilization efficiency (NUtE)—can be further improved by exploring crop variety and soil N cycling. Canola parental genotypes (NAM-0 and NAM-17) and hybrids (H151857 and H151816) were grown on a dark brown chernozem in Saskatchewan, Canada. Soil and plant samples were collected at the 5–6 leaf stage and flowering, and seeds were collected at harvest maturity. Soil N cycling varied with phenotypic stage, with higher potential ammonium oxidation rates at the 5–6 leaf stage and higher urease activity at flowering. Seed N uptake was higher under higher urea-N rates, while the converse was true for NUE metrics. Hybrids had higher yield, seed N uptake, NUtE, and NUE, with higher NUE potentially owing to higher NUtE at flowering, which led to higher yield and seed N allocation. Soil N cycling and soil N concentrations correlated for improved canola NUE, revealing below-ground breeding targets. Future studies should consider multiple root characteristics, including rhizosphere microbial N cycling, root exudates, and root system architecture, to determine the below-ground dynamics of plant NUE.

Highlights

Canola (Brassica napus) is an important oilseed crop grown globally, with Canada producing over 20.7 and 19.6 million metric tons of canola in 2018 and 2019, respectively [1], making Canada one of the largest canola producers globally
There was a two-way interaction between fertilizer N rates and phenological stage on soil NH4+-N concentration (Table 1), where NH4+-N concentration was highest under the 150 kg ha−1 N rate at both phenological stages and lowest under the 0 kg ha−1 N rate at the 5–6 leaf stage (Figure 1)
The objective of this study was to evaluate how canola varieties under varying fertilizer urea-N rates affect (1) soil N cycling processes, (2) soil N concentration, and (3) plant N use efficiency (NUE); and how this varies over the growing season

Summary

Introduction

Canola (Brassica napus) is an important oilseed crop grown globally, with Canada producing over 20.7 and 19.6 million metric tons of canola in 2018 and 2019, respectively [1], making Canada one of the largest canola producers globally. Canola is used in human consumption, animal feed, and feedstock for biofuels, requiring relatively large inputs of N to produce high yields [2,3,4,5,6,7,8,9]. There are negative environmental concerns, with excessive N fertilizer use affecting the soil and waterways through nitrate leaching and runoff [10]. The future of sustainable agriculture requires increased and stable crop yields, with decreasing amounts of N fertilization [11,12,13] to protect ecosystem health while feeding the growing population. Researchers must find solutions to maximize agronomic and economic competitiveness while reducing associated negative environmental impacts [14]. Agronomic and economic competitiveness is achievable by improving and enhancing crop N use efficiency (NUE) [11]

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