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Soil Nitrogen Cycling Processes Under Diverse Canola Genotypes

Date

2022-09-15

Journal Title

Journal ISSN

Volume Title

Publisher

ORCID

0000-0003-2401-3300

Type

Thesis

Degree Level

Masters

Abstract

Canola is one of the most important oil crops globally behind soybean and oil palm. Nitrogen (N) is one of the limiting resources for canola production, yet canola is often blamed for its low nitrogen use efficiency (NUE). This project aims to identify canola lines with consistently high NUE for further exploitation in canola breeding programs. Specifically, I sought to evaluate genotypic differences in soil N cycling processes in a field study established at two sites located on Black (Melfort) and Dark Brown (Llewelyn) Chernozems in Saskatchewan, Canada. The experiment consisted of eight canola genotypes grown under two levels of N fertility and arranged as a split-plot randomized complete block design. The abundance of microbial N cycling genes (bacterial amoA and archaeal amoA) was assessed in the rhizosphere and extracellular enzyme activities (leucine aminopeptidase; LAP and N-acetyl glucosaminidase; NAG) were determined in soils collected from the root-zone and between rows at the 6-leaf and flowering stages. Overall, the rhizosphere supported higher extracellular enzyme activities in comparison to between-row soils. Development stage was also an important factor for both LAP and NAG activities. However, for the effect of canola cultivar and N fertilization, although NAG varied significantly in soils collected in 2019, the effect of N fertilization rates and cultivar on enzyme activities was inconsistent among site-years and was not the same between LAP and NAG. For bacterial and archaeal amoA gene abundance, the effect of development stage was significant for all site-years, with the exception of the bacterial amoA gene abundance at Melfort in 2019. However, N application rate and cultivar did not have any significant influences on the gene abundances. There was positive correlation between extracellular enzyme activity and gene abundance, which indicated that the increase in extracellular enzyme activity was accompanied by the proliferation of the amoA communities. However, the effect was dependent on the site and year. Overall, extracellular enzyme activities and amoA gene abundances appear to be most strongly related to sampling locations within the plot (rhizosphere versus between row). In contrast, cultivars and N treatments did not have significant effects. Therefore, the identification of canola lines with high NUE enhance the overall economic and environmental values for canola production.

Description

Keywords

Canola, N cycling

Citation

Degree

Master of Science (M.Sc.)

Department

Soil Science

Program

Soil Science

Advisor

Part Of

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DOI

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