The nitrogen and moisture of manure are highly variable parameters and depend on animal type, husbandry techniques, environmental conditions and storage time. The precision in manure dose estimation for crops fertilization depends on the total nitrogen and moisture content just before its incorporation in the field. The aim of the study is to develop a Fourier Transform Near Infrared (FT-NIR) spectroscopy method to determine the total Kjeldhal nitrogen (TKN%) and moisture (M%) of different types of poultry manure prior to land application. Samples covering a wide range of poultry types and different husbandry conditions were obtained from farms of North-Eastern Italy in order to develop the method. The method was calibrated (R(2) = 0.94 for TKN%, R(2) = 0.99 for M%) and validated (R(2) = 0.82 for TKN%, R(2) = 0.95 for M%) in the laboratory. An external validation was also performed in situ with independent samples, of similar origin to the previous data set, which were collected just before application in the field. Spectra acquisitions for these samples were carried out using the same instrumentation which was placed in a special vehicle for monitoring campaigns. The results showed satisfactory prediction accuracy (R(2) = 0.82 for TKN%, R(2) = 0.93 for M%). Finally, an additional analysis was performed to discriminate the different types of poultry effluents. The TKN and M measurements in the disposal areas indicated that current agronomic practices lead to more than double poultry manure oversupply. The proposed FT-NIR methodology aims to improve the current fertilization management and environmental protection by providing fast and precise estimations of poultry manure doses prior to land application.
Keywords: moisture content; near infrared spectroscopy; organic fertilizers; poultry manure; total nitrogen.