Application of near infrared spectroscopy for estimating available nitrogen in poultry manure compost

The objective of this study was to develop an easy method of estimating available nitrogen in poultry manure compost using near infrared spectroscopy (NIRS). A scanning monochromator was used to obtain the reflectance spectra from 1,100 to 2,500 nm of samples of dried and milled poultry manure compost. Second derivative spectra and multiple regression analysis were used to develop calibration equations for total nitrogen (T-N) and uric acid nitrogen (UA-N). Standard error of prediction (SEP) of the best calibrations for T-N and UA-N were 4.74 mg g⁻¹ and 4.32 mg g⁻¹, respectively. The correlation between available nitrogen, which was obtained using incubation experiments, and UA-N in the compost samples was extremely high (r = 0.99999, SE = 0.61 mg g⁻¹). In conclusion, the estimation of available nitrogen from UA-N values using NIRS is a practical method of analyzing poultry manure compost.