Nitrogen Fixation: N-fixation
Symbiotic nitrogen-fixers require energy (supplied as the products of photosynthesis by the host plant) for the reduction of atmospheric dinitrogen (N2) to ammonium (NH4+).
Because these symbiotic bacteria (Rhizobium), actinomycetes (Frankia)
and cyanobacteria (Anabaena and Nostoc) live within the plant's roots,
little of the nitrogen they fix escapes into the soil and is instead 'delivered' directly to the root cells for uptake
and use throughout the plant.
Clover (Trifolium spp.) is grown extensively as a pasture species in temperate areas of Australia. N-fixing bacteria (Rhizobium) live in nodules on its roots.