Canola nitrogen use efficiency and soil nitrogen cycling in response to varying nitrogen fertilizer rates across hybrid canola varieties and their parents

@font-face {font-family:"Cambria Math"; panose-1:2 4 5 3 5 4 6 3 2 4; mso-font-charset:0; mso-generic-font-family:auto; mso-font-pitch:variable; mso-font-signature:-536870145 1107305727 0 0 415 0;}@font-face {font-family:Calibri; panose-1:2 15 5 2 2 2 4 3 2 4; mso-font-charset:0; mso-generic-font-family:auto; mso-font-pitch:variable; mso-font-signature:-536870145 1073786111 1 0 415 0;}@font-face {font-family:SimSun; panose-1:2 1 6 0 3 1 1 1 1 1; mso-font-charset:134; mso-generic-font-family:auto; mso-font-pitch:variable; mso-font-signature:3 680460288 22 0 262145 0;}@font-face {font-family:"Palatino Linotype"; panose-1:2 4 5 2 5 5 5 3 3 4; mso-font-charset:0; mso-generic-font-family:auto; mso-font-pitch:variable; mso-font-signature:-536870265 1073741843 0 0 415 0;}p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-unhide:no; mso-style-qformat:yes; mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; text-align:justify; text-justify:inter-ideograph; line-height:17.0pt; mso-pagination:widow-orphan; font-size:12.0pt; mso-bidi-font-size:10.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; color:black; mso-fareast-language:DE;}.MsoChpDefault {mso-style-type:export-only; mso-default-props:yes; font-size:10.0pt; mso-ansi-font-size:10.0pt; mso-bidi-font-size:10.0pt; font-family:Calibri; mso-ascii-font-family:Calibri; mso-fareast-font-family:SimSun; mso-hansi-font-family:Calibri;}div.WordSection1 {page:WordSection1;} Improving nitrogen use efficiency (NUE) is essential for sustainable agriculture, especially in high N demanding crops such as canola (<i>Brassica napus</i>). While advancements in aboveground agronomic practices have improved NUE, research on soil and belowground 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 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 belowground breeding targets.