Post-anthesis Relationships Between Nitrogen Isotope Discrimination and Yield of Spring Wheat Under Different Nitrogen Levels

Abstract

Wheat grain yield and nitrogen (N) content are influenced by the amount of N remobilized to the grain, together with pre-anthesis and post-anthesis N uptake. Isotopic techniques in farmed areas may provide insight into the mechanism underlying the N cycle. 15N-labeled urea was applied to microplots within five different fertilized treatments 0 kg ha–1 (N1), 52.5 kg ha–1 (N2), 105 kg ha–1 (N3), 157.5 kg ha–1 (N4), and 210 kg ha–1 (N5) of a long-term field trial (2003–2021) in a rainfed wheat field in the semi-arid loess Plateau, China, to determine post-anthesis N uptake and remobilization into the grain, as well as the variability of 15N enrichment in aboveground parts. Total N uptake was between 7.88 and 29.27 kg ha–1 for straw and 41.85 and 95.27 kg ha–1 for grain. In comparison to N1, N fertilization increased straw and grain N uptake by 73.1 and 56.1%, respectively. Nitrogen use efficiency (NUE) and harvest index were altered by N application rates. The average NUE at maturity was 19.9% in 2020 and 20.01% in 2021; however, it was usually higher under the control and low N conditions. The amount of 15N excess increased as the N rate increased: N5 had the highest 15N excess at the maturity stage in the upper (2.28 ± 0.36%), the middle (1.77 ± 0.28%), and the lower portion (1.68 ± 1.01%). Compared to N1, N fertilization (N2–N5) increased 15N excess in the various shoot portions by 50, 38, and 35% at maturity for upper, middle, and lower portions, respectively. At maturity, the 15N excess remobilized to the grain under N1–N5 was between 5 and 8%. Our findings revealed that N had a significant impact on yield and N isotope discrimination in spring wheat that these two parameters can interact, and that future research on the relationship between yield and N isotope discrimination in spring wheat should take these factors into account.

Comparative study of urea-15N fate in pure bamboo and bamboo-broadleaf mixed forests

“…In this study, the participation of p. chinense ‘s litter in decomposition led to higher organic matter content in all soil layers of Q-P type compared to Q type, consequently immobilizing more nitrogen. The residual 15 N in both forest types exhibited a decreasing trend with increasing soil depth, consistent with previous reports ( Ru et al., 2020 ; Nguyen et al., 2021 ; Effah et al., 2022 ).…”

Morphology and Nitrogen Uptake and Distribution of Wheat Plants as Influenced by Applying Remedial Urea Prior to or Post Low-Temperature Stress at Seedling Stage

“…Hence, in order to explore the different nitrogen absorption between the treatments with nitrogen applied prior to or post low-temperature stress, stable (N-15) isotope-labelled urea was used. Nitrogen content in the wheat plants was increased with increased nitrogen application rate by isotopic techniques [36]. From our results of 15 N labelled urea amendment experiment, the percentage of total nitrogen from 15 N urea was more than 10% higher under N-LT than that under LT-N, indicating that nitrogen applied prior to low temperature better mitigated the injury of wheat roots caused by low-temperature stress (Table 3).…”