Measuring '%Ndfa' and 'Biological Nitrogen Fixation'

Measuring biological nitrogen fixation (BNF) is an important agronomic and agroecological trait of legumes. The trait is often neglected yet it is an indicator of crop performance with respect to a plant’s capacity to derive nitrogen from air via BNF. This process is mediated by soil bacteria, collectively termed rhizobia, that form a symbiosis with the legume. The rhizobia are contained within legume root nodules and here in the nodule core (a microaerophilic environment), the rhizobia fix largely inert atmospheric di-nitrogen gas into biologically useful nitrogen compounds. These compounds are shared with the host plant in exchange for energy in the form of photosynthate. The process of measuring BNF comprises two stages