what is free nitrogen?\no nitrogen that is ready for plants to use\no nitrogen that has been fixed by…

Brief Explanations:

Free nitrogen refers to nitrogen in its molecular form ($N_2$) in the atmosphere. It cannot be directly used by most organisms as they lack the ability to break the strong triple - bond in $N_2$. Nitrogen needs to be fixed (converted to ammonia or other nitrogen - containing compounds) by bacteria or through industrial processes to be usable by organisms.

Answer:

nitrogen that cannot be used by organisms