Ciampitti Ignacio A, de Borja Reis André Froes, Córdova S Carolina, Castellano Michael J, Archontoulis Sotirios V, Correndo Adrian A, Antunes De Almeida Luiz Felipe, Moro Rosso Luiz H
Department of Agronomy, Kansas State University, Manhattan, KS, United States.
Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, MI, United States.
Front Plant Sci. 2021 Oct 7;12:727021. doi: 10.3389/fpls.2021.727021. eCollection 2021.
Biological nitrogen (N) fixation is the most relevant process in soybeans ( 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) and N derived from the atmosphere [Ndfa (%)] to define: (i) time to the maximum rate of N fixation (β), (ii) time to the maximum Ndfa (α), 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 (β) 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.
生物固氮是大豆满足植株氮需求并维持种子蛋白质形成的最关键过程。过去关于田间种植大豆固氮的研究主要集中在单一时间点的测量（主要是在生长季末期）以及部分氮预算（固定氮减去种子氮移除量），而忽略了这一过程的季节性模式。因此，本研究整合了作物生长季内多个时间点测量的田间数据集，利用固定氮（千克/公顷）和来自大气的氮[大气氮贡献率（%）]来表征固氮动态，以确定：（i）固氮最大速率出现的时间（β），（ii）大气氮贡献率最高时的时间（α），以及（iii）累积固定氮量。本研究的主要结果是：（1）固氮最大速率出现在结荚初期（R3期）左右；（2）大气氮贡献率最高时的时间出现在满荚期（R4期）之后；（3）累积固氮量与季节性蒸气压亏缺（VPD）和生长周期长度呈正相关，但与土壤黏土含量呈负相关；（4）固氮最大速率出现的时间（β）受季节长度的正向影响，在营养生长阶段受高温的负向影响（但在同一时期受VPD的正向影响）。总体而言，固氮最大速率出现时间的变化范围比大气氮贡献率最高时的时间变化范围窄得多，后者根据评估研究的不同，从开花期（R1期）到种子灌浆期（R5 - R6期）变化很大。从表型分析的角度来看，在R4生长阶段之后进行固氮测定最有可能同时捕捉到最大固定氮速率和最大大气氮贡献率（%）。应开展更深入的研究，更密切地探究固氮与土壤 - 植物 - 环境因素之间的相互作用。
