When plants take in air they also take in nitrogen so why is nitrogen- fixation needed?
Taking it in is not the same as fixing it – we breathe in air but we can’t make any use of the nitrogen in the air and the same applies to plants. As far as the plant is concerned the nitrogen that enters a plant’s leaves is inert. The plant needs nitrogen-fixing bacteria (nitrobacter) to convert gaseous nitrogen N2 into nitrogenous compounds that the plant can use. Plants which do not contain nitrobacter must obtain all their nitrogen in the form of compounds already in the soil.
