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

Zechariah Effah; Lingling Li; Junhong Xie; Benjamin Karikari; Jinbin Wang; Min Zeng; Linlin Wang; Solomon Boamah; Jagadabhi Padma Shanthi

doi:10.3389/fpls.2022.859655

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

Front Plant Sci. 2022 Mar 17:13:859655. doi: 10.3389/fpls.2022.859655. eCollection 2022.

Authors

Zechariah Effah^{1

2

3}, Lingling Li^{1

2}, Junhong Xie^{1

2}, Benjamin Karikari⁴, Jinbin Wang^{1

2}, Min Zeng^{1

2}, Linlin Wang^{1

2}, Solomon Boamah⁵, Jagadabhi Padma Shanthi⁶

Affiliations

¹ State Key Laboratory of Arid Land Crop Science, Lanzhou, China.
² College of Agronomy, Gansu Agricultural University, Lanzhou, China.
³ Council for Scientific and Industrial Research (CSIR)-Plant Genetic Resources Research Institute, Bunso, Ghana.
⁴ Department of Crop Science, Faculty of Agriculture, Food and Consumer Sciences, University for Development Studies, Tamale, Ghana.
⁵ Biocontrol Engineering Laboratory of Crop Diseases and Pests of Gansu Province, College of Plant Protection, Gansu Agricultural University, Lanzhou, China.
⁶ Action for Climate and Environment Program, Dr. Reddy's Foundation, Hyderabad, India.

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.

Keywords: 15N labeling; N remobilization; harvest index; nitrogen uptake; sustainable production.