Nitrogen in soil is considered a saturated solution. In chemistry, a saturated solution is one where a solute is dissolved in a solvent to the maximum extent possible at a given temperature and pressure. Any addition of solute beyond this point will not dissolve in the solvent and will settle out as a precipitate or remain undissolved.
In the context of soil, nitrogen acts as a solute, and the soil acts as a solvent. The soil can hold a certain amount of nitrogen, and once it reaches its capacity, it becomes saturated. Hence, the correct answer is "Saturated."