Development and Testing of a Portable Soil Nitrogen Detector Based on Near-infrared Spectroscopy

Access to soil information is accompanied by the entire agricultural production process. The conventional method (Physicochemical analysis) for detection of nitrogen in soil is complex and time-consuming. In this work, we present a portable soil nitrogen detector by using a chip-scale Fourier transform infrared spectroscopy sensor to enable rapid detection of soil nitrogen, and a supporting software with functions such as spectral acquisition, background subtraction, and data storage was also program. The detector was used to detect the spectral data in the actual farmland environment. 120 randomly selected soil samples were used to calibrate soil nitrogen to soil reflectance using partial least squares. 76 randomly selected samples were withheld for validation. Results of the experiments indicated values for the coefficient of determination as high as 0.934, and root mean square error was 1.923. After the model was embedded in detector, 10 soil samples were tested for verification. The relative error between the predicted value and the real value was less than 13%, and the minimum relative error was 5.56%. The results verified that detector can initially realize the rapid prediction of soil nitrogen and provide a certain technical reference for miniaturization of portable detecting instruments.