Revisiting Biological Nitrogen Fixation Dynamics in Soybeans

Ignacio A Ciampitti; André Froes de Borja Reis; S Carolina Córdova; Michael J Castellano; Sotirios V Archontoulis; Adrian A Correndo; Luiz Felipe Antunes De Almeida; Luiz H Moro Rosso

doi:10.3389/fpls.2021.727021

Revisiting Biological Nitrogen Fixation Dynamics in Soybeans

Front Plant Sci. 2021 Oct 7:12:727021. doi: 10.3389/fpls.2021.727021. eCollection 2021.

Authors

Ignacio A Ciampitti¹, André Froes de Borja Reis¹, S Carolina Córdova^{2

3

4}, Michael J Castellano⁵, Sotirios V Archontoulis⁵, Adrian A Correndo¹, Luiz Felipe Antunes De Almeida¹, Luiz H Moro Rosso¹

Affiliations

¹ Department of Agronomy, Kansas State University, Manhattan, KS, United States.
² Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, MI, United States.
³ W. K. Kellogg Biological Station, Michigan State University, Hickory Corners, MI, United States.
⁴ Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI, United States.
⁵ Department of Agronomy, Iowa State University, Ames, IA, United States.

Abstract

Biological nitrogen (N) fixation is the most relevant process in soybeans (Glycine max L.) to satisfy plant N demand and sustain seed protein formation. Past studies describing N fixation for field-grown soybeans mainly focused on a single point time measurement (mainly toward the end of the season) and on the partial N budget (fixed-N minus seed N removal), overlooking the seasonal pattern of this process. Therefore, this study synthesized field datasets involving multiple temporal measurements during the crop growing season to characterize N fixation dynamics using both fixed-N (kg ha^-1) and N derived from the atmosphere [Ndfa (%)] to define: (i) time to the maximum rate of N fixation (β₂), (ii) time to the maximum Ndfa (α₂), and (iii) the cumulative fixed-N. The main outcomes of this study are that (1) the maximum rate of N fixation was around the beginning of pod formation (R3 stage), (2) time to the maximum Ndfa (%) was after full pod formation (R4), and (3) cumulative fixation was positively associated with the seasonal vapor-pressure deficit (VPD) and growth cycle length but negatively associated with soil clay content, and (4) time to the maximum N fixation rate (β₂) was positively impacted by season length and negatively impacted by high temperatures during vegetative growth (but positively for VPD, during the same period). Overall, variation in the timing of the maximum rate of N fixation occurred within a much narrower range of growth stages (R3) than the timing of the maximum Ndfa (%), which varied broadly from flowering (R1) to seed filing (R5-R6) depending on the evaluated studies. From a phenotyping standpoint, N fixation determinations after the R4 growth stage would most likely permit capturing both maximum fixed-N rate and maximum Ndfa (%). Further investigations that more closely screen the interplay between N fixation with soil-plant-environment factors should be pursued.

Keywords: N derived from the atmosphere; biological N fixation; soil; soybeans; weather.