Biological nitrogen fixation (BNF) in legume root nodules is an important source of N globally. Typically, the quantification of BNF is an estimate of N fixation through techniques such as an acetylene reduction assay or isotopic signatures. However, these methods have large logistical limitations, and do not allow for assessments of the nodule morphology or the nodulation process itself, knowledge that is important to fully understand the BNF process. To provide an updated method of nodulation assessments, peanut (Arachis hypogaea L.) nodules were sampled from a two-year field trial and quantified using scanned images of excised nodules, allowing digital assessment of nodule number and size. Further, a digital color analysis method was developed to assess internal nodule color (a known proxy for nodule BNF activity and senescence). To apply and evaluate the new method, peanut nodulation trait data was used for an exploration of the relationship between nodulation traits, plant physiological processes, and nitrogen status in the plant, followed by a nodulation life history analysis. The nodulation assessment method was confirmed by strong correlation with measures of peanut tissue N, biomass, photosynthetic function, and yield. Nodulation life history data suggest novel findings regarding differences in the development of nodules between taproots and lateral roots, contrary to the previous understanding of peanut nodulation life history. This new nodulation assessment method can provide further insight into the BNF process by allowing the collection of detailed data in a relatively simplified manner in field conditions.

豆科植物根瘤中的生物固氮（BNF）是全球范围内氮的重要来源。通常，BNF的定量是通过乙炔还原测定或同位素标记等技术对N固定的估计。但是，这些方法在逻辑上有很大的局限性，并且不允许评估结节形态或结节过程本身，而这对于充分理解BNF过程至关重要。为了提供更新的结瘤评估方法，花生（花生）L.）结节是从一项为期两年的野外试验中取样的，并使用切除结节的扫描图像进行了量化，从而可以对结节的数量和大小进行数字评估。此外，开发了一种数字颜色分析方法以评估内部结节颜色（结节BNF活性和衰老的已知替代方法）。为了应用和评价该新方法，花生根瘤性状数据被用于探索根瘤性状，植物生理过程和植物中氮含量之间的关系，然后进行根瘤生活史分析。结瘤评估方法通过与花生组织氮，生物量，光合功能和产量的相关性强而得到证实。结瘤生活史数据表明有关根部和侧根之间的结节发育差异的新发现，与以前对花生节结生活史的认识相反。通过允许在野外条件下以相对简化的方式收集详细数据，这种新的结瘤评估方法可以提供对BNF过程的进一步了解。