How do plants obtain nitrogen?

Plants take nitrogen from the soil by absorption through their roots as amino acids, nitrate ions, nitrite ions, or ammonium ions. Plants do not get their nitrogen directly from the air ... Plants get the nitrogen that they need from the soil, where it has already been fixed by bacteria and archaea.

Answer: Plants obtain nitrogen through a natural process. Nitrogen is introduced to the soil by fertilizers or animal and plant residues. Bacteria in the soil convert the nitrogen to ammonium and nitrate, which is taken up by the plants by a process of nitrogen fixation.