Inorganic and Mineralizable Nitrogen in Poultry Litter by Near-Infrared Reflectance.

Assessing the nitrogen (N) fertilizer value of poultry litter (PL) relative to chemical sources is routinely based on measurement of total N .  A portion of this N may be unavailable to plants and so total N can be a poor predictor of field crop response.  Better characterization of the mineral and potentially mineralizable forms of N will improve prediction of N availability in PL.  Near infrared reflectance (NIR) spectroscopy is a rapid analysis tool that has shown promise in assessing some forms of poultry litter N.  Nearly all of the research into this area has been performed on PL that has been freeze-dried and pulverized to a powder-like product.  Such intense sample processing is expensive for agricultural laboratories, and can cause N transformation and/or loss prior to analysis.  The results presented here show that NIR calibrations for total-, ammonium-, nitrate-, and potentially mineralizable-N can be produced with samples on an ‘as received’ moisture basis with minimal homogenization that are equivalent to previously published  work with intensely processed samples.  This is the first known research to present successful calibration for uric acid-N in poultry litter.  Furthermore, the inclusion of broiler, pullet, and layer derived PL in the calibration process demonstrates the effectiveness of NIR as a routine analysis tool for assessing the N availability in poultry litter.