Nitrate-Nitrogen (NO3-N) losses to ground and surface water are an environmental and agronomic concern inmodern crop production systems in the Central Great Plains. Monitoring techniques for nitrogen use in agriculturalproduction are needed to increase crop yield, optimize nitrogen use, and reduce NO3-N leaching. Time domain reflectometry(TDR) could potentially be calibrated to continuously measure NO3-N in soil and water. The objectives of this study were to:(1) evaluate the effect of different factors affecting the response of the bulk electrical conductivity (ECb) sensed by TDR, (2)compare the sensitivity and differences between vertically-installed and horizontally-installed probes for measuring NO3-Nleaching in the soil profile, and (3) evaluate the feasibility of using TDR to measure changes in NO3-N concentration in anirrigated agricultural soil. Studies were conducted in the laboratory and in the field at the University of Nebraska WestCentral Research and Extension Center in North Platte, Nebraska. Temperature of the medium (Ts), solute concentration,TDR cable length, and volumetric soil water content (.v) all influenced and were linearly related to the bulk electricalconductivity (ECb) sensed by the TDR probes. In the field, measured soil NO3-N correlated well with values estimated usingTDR measurements of ECb, corrected for changes in .v and Ts. These results indicated that TDR, if properly calibrated fora particular soil, could be used to continuously monitor NO3-N in soil, and should also be well-suited for monitoring NO3-Nin groundwater and surface water. It is, however, important to perform the calibration over a long enough period of time toinclude the expected range of .v, Ts, and NO3-N values to obtain adequate accuracy.