The common nitrogen -fixer in paddy field is
Rhizobium
Azopirillum
Oscillatoria
Oscillatoria
B.
Azopirillum
Azopirillum is a nitrogen-fixing bacterium in paddy fields. It is very useful soil and root bacterium. It is an associative symbiotic N2 -fixing bacteria. When it is added to the soil, it multiplies in millions and can supply 20-40 kg of nitrogen per hectare per season. It also produces growth promoting substance like Indole Acetic acid (IAA). Gibberellins and promotes root proliferation. These substances improve the plant growth and yield.