In our new paper, out in Soil Biology and Biochemistry, we used isotopic tracers in laboratory, greenhouse, and field settings to measure nitrogen (N) fixation in switchgrass. Our results suggest that bacteria associated with switchgrass fix N episodically – meaning fixation sometimes occurs at a high rate and is undetectable other times – perhaps in response to transiently appropriate physicochemical conditions. Metagenomic analyses revealed a wide diversity of bacterial taxa in and around switchgrass are capable of fixing N. We still don’t know if fixation is an important source of N to perennial grasses. If fixation is important in the switchgrass N budget, those inputs may occur in periodic bursts of fixation activity.

Citation: Roley, S.S., Xue, C., Hamilton, S.K., Tiedje, J.M., and Robertson, G.P. 2019. Episodic nitrogen fixation in switchgrass (Panicum virgatum L.). Soil Biology and Biochemistry.129: 90-98. doi: 10.1016/j.soilbio.2018.11.006