Fast and reliable methods for monitoring soil nitrate-nitrogen (NO₃-N) concentration is vital for reducing NO₃-N losses to ground and surface water in agricultural production. In-situ measurement of nitrogen content can increase crop yield, optimize fertilizer use, and reduce environmental problems caused by high level of nitrate in water. Dielectric properties of a bulk soil have been intensively used to estimate its volumetric water content, salinity and, in some cases, NO₃-N concentration employing time domain reflectometry (TDR), but no study have been done to evaluate an effect of soil nitrogen level on spectral response. Thus the goal of the work was to study the effect of NO₃-N concentration on soil dielectric response at different moisture content using frequency domain techniques. We also examined the effect of global ionic concentration on the nitrogen-induced response using chloride ions as a “background” anion.