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 validate 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 validated 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. This dataset represents the nodulation and other variable data collected for this study.

Data was collected in a field study in Live Oak, Florida in peanut using a novel nodulation assessment technique at 40, 60, 80, 100, 120, and 140 DAP in 2016 and 2017. This technique used digital imaging software to calculate the nodulation density (nodules per cm root), nodule size, average internal redness of nodules (activity), and average internal greenness of nodules (senescence). Nodule biomass was also measured, as was root, shoot, and pod biomass of peanut plants. The N mass in these tissue samples was also calculated. In addition, chlorophyll a fluorescence data was collected as a correlate. Data was collected across three treatment levels in a RCBD, with data considered across these three treatment levels for correlation purposes. The treatment levels relate to the N application rate to corn in the season before the peanut was grown and sampled in the field. These nodulation data have been collected using a novel moethod developed for this purpose. 

Missing values exist where sampling was physiologically impossible (i.e., peanut pods in the early season), or occassionally as the result of error or damage. Such instances are highlighted in yellow in the datasheet. See also "Appendix B" regarding missing values at 80 DAP in 2016.