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Title: NEAR- VERSUS MID-INFRARED DIFFUSE REFLECTANCE SPECTROSCOPY FOR THE ANALYSISOF DRIED DAIRY MANURES

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

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/1/2002
Publication Date: 1/31/2002
Citation: N/A

Interpretive Summary: Spectroscopy utilizes the interaction of light with materials to determine their composition. Two forms of spectroscopy (near- and mid-infrared) use light beyond the range of human sight to determine the composition of animal feeds and similar materials. Calibrations are developed which relate the composition of the material of interest to the interactions found with the light used. The objective of this investigation was to examine the ability of near- and mid-infrared diffuse reflectance spectroscopy to determine the composition of dried dairy manures. Samples were dried at 60o C, ground and scanned in the near-infrared and in the mid-infrared. While calibrations for various measures of manure organic composition were found to be possible, the results were generally less accurate than found for similar determinations in animal feeds, such as forages. Results were generally somewhat better based on mid-infrared spectra vs. near, but again were not as accurate as found with forages. Examination of the composition of the dried manures indicated that high ash contents (8 to 52% of dry matter) might be the cause for the decrease in calibration accuracy. However, comparison of calibrations based on dry matter to those on an ash-free basis showed no clear preference for either means of computation. Finally, neither spectral range was able to accurately determine minerals such as potassium or phosphorus (calibrations may be useful for gross segregation).

Technical Abstract: The objective of this investigation was to examine the ability of near- and mid-infrared diffuse reflectance spectroscopy to determine the composition of dried dairy manures. Samples (n = 99) were dried at 60o C, ground and scanned in the near-infrared in a rotating sample cup on a FOSS-NIRSystems model 6500 scanning monochromator, and in the mid-infrared on a Digi-Lab FTS60 Fourier Transform spectrometer using a custom made sample transport. While calibrations for various measures of fiber composition (neutral and acid detergent fiber, etc.) were found to be possible, the results were generally less accurate than found for similar determinations in forages. Results were generally somewhat better based on mid- infrared spectra vs. near, but again were not as accurate as found with forages. Examination of the composition of the dried manures indicated that high ash contents (8 to 52% of dry matter) might be the cause for the decrease in calibration accuracy. However, comparison of calibrations based on dry matter to those on an ash- free basis showed no clear preference for either means of computation. Neither spectral range was able to accurately determine minerals such as K or P (calibrations may be useful for gross segregation). Finally, calibrations based on mid-infrared spectra showed some potential for helping to understand the relationship between manure composition and N mineralization potential.