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United States Department of Agriculture

Agricultural Research Service

Title: Investigations into Near-Infrared Analysis As An Alternative to Traditionalprocedures in Manure Nitrogen and Carbon Mineralization Studies

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

Submitted to: Near Infrared Spectroscopy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 24, 1998
Publication Date: N/A

Interpretive Summary: In order to evaluate the availability of nutrients in dairy manure as potential sources of nutrients for plants, assays known as mineralizations are performed. These assays involved incubating manures with soil to evaluate the availability of nitrogen. These assays are time consuming and labor intensive and a quicker method would be very beneficial. Near-infrared spectroscopy (NIRS) is a technique using light invisible to humans which has come to be used to replace many assays similar to those used during mineralization studies. The objective of this investigation was to determine the feasibility of using NIRS to determine nitrogen and carbon mineralization rates and extents in dairy manures. NIRS was investigated for determining ammonia, nitrate, and Total-N (ammonia and nitrate) contents, and carbon evolved as carbon dioxide. Results by NIRS were compared to the chemical assays normally performed. Results using 593 samples have shown that, while the use of NIRS to replace traditional assays may be possible for the type of samples studied here, their development will require great care with respect to the samples to be analyzed. While it appears that the source of the manure with respect to the diet of the animal(s) was not a serious consideration, manure storage conditions prior to incubation were. In summary, results indicated that NIRS may have potential for analyzing manure-amended and non-amended soils from mineralization experiments, but further work is needed to determine it's true potential.

Technical Abstract: The objective of this investigation was to determine the feasibility of using NIRS to determine N and C mineralization rates and extents in dairy manures. Ground soil samples from studies in which manure was incubated with soil for various time periods (0 to 112 d) were scanned in the NIR (1100 to 2498 nm) using a scanning monochromator equipped with a rotating sample cup. Control samples (soil alone) were also scanned and tested. Calibrations for NH3, nitrate, Total-N (NH3 and nitrate) contents, and C evolved as CO2 were developed. Calibration values for NH3 and nitrate were determined on KCl soil extracts using a Technicon autoanalyzer. Carbon dioxide values were determined by titrating evolved CO2 that was trapped using KOH solution. All calibrations were developed using Partial Least Squares regression analysis. Results using 593 samples from several mineralization experiments have shown that, while NIRS calibrations for NH3, nitrate, Total-N and evolved CO2 may be possible, their development will require great care with respect to the samples to be covered by the calibration. While it appears that the source of the manure with respect to the diet of the animal(s) was not a serious consideration, manure storage conditions prior to incubation had a strong influence on calibration results. In addition, separate calibrations appear to be needed for control and non-control samples. In summary, results presented here, indicate that NIRS may have potential for analyzing manure-amended and non-amended soils from mineralization experiments, but further work is needed to determine it's true potential.

Last Modified: 4/24/2014
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