On Farm Validation of different NIR Sensors for Manure Sensing

Several mobile and one benchtop sensors for measuring the constitutions in manure are validated on farms with typical animal production like cattle, hog and biogas production in northern Germany, Schleswig-Holstein. For the mobile sensors, some cubic meters of manure were pumped through a test line of a mobile test bench with five near infrared NIR sensors in parallel use. The benchtop sensor – a nuclear magnetic resonance NMR Spectrometer-was measuring a subsample of the pumped material which was also used for reference analysis in three external laboratories. The sensors are different in their results compared with the reference. For total nitrogen one mobile NIR sensor differs in average about 80 % to the reference expressed by the standard error of validation RMSE related to the mean reference while the four others have a deviation of about 30 %. For ammonium this kind of accuracy is about 40 % for the four NIR sensors, for dry matter about 20 %. The NMR sensor performs contrary. It shows a relative RMSE of less than 20 % for total nitrogen and less than 10 % for ammonium, but about 40 % for dry matter. The poor performance of the NIR sensors cannot be explained by deviations in the presentation or sampling process. It is assumed that the tested samples do not fit well to the calibration of the NIR sensors. © 2022, VDI Verlag GMBH. All rights reserved.