Precision Agric https://doi.org/10.1007/s11119-018-9579-0 1 3 Development of feld mobile soil nitrate sensor technology to facilitate precision fertilizer management Natalia Rogovska 1  · David A. Laird 1  · Chien‑Ping Chiou 2  · Leonard J. Bond 2 © Springer Science+Business Media, LLC, part of Springer Nature 2018 Abstract Precision nitrogen (N) fertilizer management has the potential to improve N fertilizer use efciency, simultaneously reducing the cost of inputs for farmers and the of- site environmental impact of crop production. Although technology is available to spatially vary sidedress N fertilizer application rates within felds, sensor technology capable of measuring soil nitrate (NO 3 − ) levels in-real-time and on-the-go with sufcient accuracy to facilitate precision application of N fertilizers is lacking. The potential of Diamond-Atten- uated Total internal Refectance (D-ATR) Fourier Transform Infrared (FTIR) spectroscopy was evaluated as a soil NO 3 −  sensor. Two independent datasets were tested; (1) the feld dataset consisted of 124 GPS registered soil samples collected from four agricultural felds; and (2) the laboratory dataset consisted of fve diferent soils spiked with various amounts of KNO 3 (135 samples) and incubated in the laboratory. Spectra were collected using an Agilent 4100 Exoscan FTIR spectrometer equipped with a D-ATR cell and analyzed using partial least squares regression. Calibration R 2  values (D-ATR-FTIR predicted versus inde- pendently measured soil NO 3 −  concentrations) for the feld and laboratory datasets were 0.83 and 0.90 (RMSE = 8.3 and 8.8 mg kg −1 ), respectively; and robust “leave one feld/ soil out” cross validation tests yielded R 2 values for the feld and laboratory datasets of 0.65 and 0.83 (RMSE = 12.5 and 13.3 mg kg −1 ), respectively. The study demonstrates the potential of using D-ATR-FTIR spectroscopy for rapid feld-mobile determination of soil NO 3 −  concentrations. Keywords Soil nitrate sensor · Late spring nitrate test · Variable rate N fertilization · On-the-go nitrate sensing · Fourier Transform Infrared spectroscopy * David A. Laird dalaird@iastate.edu 1 Department of Agronomy, Iowa State University, Ames, IA 50011, USA 2 Center for Nondestructive Evaluation, Iowa State University, Ames, IA 50011, USA