Question

identifying parts of the nitrogen
what is free nitrogen?
nitrogen that is ready for plants to use
nitrogen that has been fixed by bacteria
nitrogen that cannot be used by organisms
nitrogen that is returned to the soil by decomposers

Explanation:

Free nitrogen refers to nitrogen in its elemental form (\(N_2\)) which makes up about 78% of the Earth's atmosphere. Plants cannot directly use this form of nitrogen. Nitrogen that is ready for plants to use (\(NO_3^-\), \(NH_4^+\)) is fixed nitrogen (not free nitrogen). Nitrogen fixed by bacteria is also in a usable form (not free). Nitrogen returned to the soil by decomposers is in forms like ammonia (\(NH_3\)) which is also a usable form (not free). Free nitrogen (\(N_2\)) cannot be used by most organisms as they lack the enzymes (like nitrogenase in nitrogen - fixing bacteria) to break the strong triple bond in \(N_2\).

Answer:

nitrogen that cannot be used by organisms