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Title:   Author  item
                                            Reeves  Iii, Jamesitem
                                            McCarty, Gregoryitem
                                            FOLLETT, R - SPNRUitem
                                            KIMBLE, J - SPNRUitem
                                            REEVES, V - FDA
  Submitted to: Agronomy Abstracts
                                    Publication Type: Proceedings
                                    Publication Acceptance Date: 9/8/2001
                                    Publication  Date: N/A
                                    Citation: N/AInterpretive Summary:
                                Technical Abstract: Two hundred and thirty-seven soil samples were collected in the western US (area from the Canadian border to Texas and west of the Missouri River to the Rockies), and a sub-sample acidified. Samples were dried (105 C) and ground prior to analysis. Samples were scanned in the mid-infrared (MIDIR) on a Digilab  FTS-60 spectrometer equipped with a custom made sample transport (50 by 2 mm area scanned), and in the near-infrared (NIR) on a NIRSystems model 6500 spectrometer (rotating sample cup). Calibrations were developed using partial least squares regression and one-out cross validation.   Mean and (STD) values for total-C, inorganic-C and organic-C were 18.3 (15.6), 6.19 (10.8), and 12.1 (13.3), respectively.   Final calibrations for organic-C using 237 acidified samples gave r2 of .984 and .854  based on MIDIR and NIR spectra, respectively.   For non-acidified samples, final MIDIR calibrations gave r2 of .957, .990 and .971 for organic-, inorganic- and total-C, respectively, while NIR results gave r2 of .890, .965 and .901 for organic-, inorganic- and total-C, respectively.   These results demonstrate that while accurate calibrations for organic-, inorganic- and total-C in diverse sets of samples can be developed using either NIR or MIDIR spectra, MIDIR results are more accurate.


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