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United States Department of Agriculture

Agricultural Research Service

Title: Determination of Ammonium-N, Moisture, Total C and Total N in Dairy Manuresusing Fiber-Optic Based Near-Infrared and Visible-Shortwave-Near-Infrared Spectrometers

Authors
item Reeves Iii, James
item Van Kessel, Jo Ann

Submitted to: Near Infrared Spectroscopy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 28, 2000
Publication Date: June 21, 2000

Interpretive Summary: Near Infrared Reflectance Spectroscopy (NIRS) is an instrumental method which uses light to determine the composition of materials such as forages. The objective of this study was to investigate the feasibility of using fiber-optic based spectrometers to estimate nutrient concentrations in dairy manures. 107 diverse manures, collected from dairy farms in the NE US were assayed spectroscopically and by conventional means for total C and N, NH3-N, moisture, P and K. Samples were scanned on two fiber-optic based instruments. Results using two fiber-optic based spectrometers have demonstrated the following: 1) Accurate calibrations for ammonium-N, moisture, and total C and N can be developed, but are not as accurate as those developed using a sample transport device; 2) While deterinations based on spectra covering the region from 400 to 2300 nm appear to be a viable alternative to manure Quick Tests already on the market, those using only the shortwave-NIR region of the spectra (400 to 1100 nm) are not; and 3) Further work with larger data sets is needed to better determine the feasibility, limitations and requirements for developing accurate and robust calibrations for manure constituents using fiber-optic based spectrometers, regardless of the spectral region used.

Technical Abstract: The objective of this study was to investigate the feasibility of using near-Infrared or visible-shortwave near-infrared fiber-optic based spectrometers to estimate nutrient concentrations in dairy manures. 107 diverse manures, collected from dairy farms in the NE US were assayed spectroscopically and by conventional means for total C and N, NH3-N, moisture, P and K. Samples were scanned on a FOSS-NIRSytems Model 6500 scanning monochromator equipped with a fiber-optic probe from 400 to 2498 nm, and on a Ocean-Optics model S2000 CCD, fiber-optic probe spectrometer from 430 to 1100 nm. Calibrations were developed using the one-out cross validation procedure using Partial Least Squares Regression. Results using two fiber-optic based spectrometers have demonstrated the following: 1) Accurate calibrations for ammonium-N, moisture, and total C and N can be developed, but are not as accurate as those developed using a sample transport device; 2) While determinations based on spectra covering the region from 400 to 2300 nm appear to be a viable alternative to manure Quick Tests already on the market, those using only the shortwave-NIR region of the spectra are not; and 3) Further work with larger data sets is needed to better determine the feasibility, limitations and requirements for developing accurate and robust calibrations for manure constituents using fiber-optic based spectrometers, regardless of the spectral region used.

Last Modified: 4/20/2014
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