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Title:   Author  item
                                            Reeves  Iii, Jamesitem
                                            McCarty, Gregory
  Submitted to: Near Infrared Reflectance International Conference Proceedings
                                    Publication Type: Proceedings
                                    Publication Acceptance Date: 6/17/1999
                                    Publication  Date: N/A
                                    Citation: N/AInterpretive Summary: Near-infrared reflectance spectroscopy (NIRS) is a technique using light which can be used to determine the composition of a wide variety of materials.  The objective of this work was to investigate the potential of NIRS under conditions where variations in the inorganic constituents of the soil were  present.  Three sets of samples were investigated: First, a set of 64 samples randomly collected from a 20 ha agricultural field which was part of a small watershed and contained a wide variety of soils.  Second, a set of 547 samples (one sample lost) collected in a grid pattern from the soil surface (0 - 10 cm) and sub-surface (10 - 30 cm) at 274 locations from the same 20 ha field.  Third, a set of 179 samples collected for a previous study from two different sites, but with less diverse soils, for  which NIRS had been shown to work very well.  Results demonstrated that accurate determinations of carbon and to a lesser extent nitrogen can be developed using near-infrared spectra for diverse sets of soil samples.  However, these preliminary results indicate that calibrations developed using less diverse sets of soil samples may be more accurate.  Results also showed that NIRS worked considerably better when applied to ground soil samples.  In conclusion, while further work is needed, results demonstrated that NIRS can be extremely useful in the analysis of the large sample sets required for determining soil composition over large areas.
                                Technical Abstract: The objective of this work was to investigate the potential of near-infrared reflectance spectroscopy (NIRS) under conditions where variations in the inorganic constituents of the soil were present.  Three sets of samples were investigated:  First, a set of 64 samples were randomly collected from a 20 ha agricultural field  which comprised a substantial part of a toposequence within a small watershed.  Second, a set of 547 samples (one sample lost) collected in a grid pattern from the soil surface (0 - 10 cm) and sub-surface (10 - 30 cm) at 274 locations from the same 20 ha field.  Third, a set of 179 samples collected for a previous study from two different sites for which NIRS had been shown to work very well.  All samples were analyzed by combustion for C and N, and scanned from 400 to 2498 nm using a scanning  monochromator and rotating sample cup.  Results of PLS calibrations demonstrated that accurate calibrations for C and to a lesser extent N can be developed using near-infrared spectra for diverse sets of soil samples.  However, these preliminary results indicate that calibrations developed using less diverse sets of soil samples may be more accurate.  Results also showed that, at least when scanned using a rotating sample, near-infrared calibrations worked considerably better when applied to ground soil samples.  In conclusion, while further work is needed, results demonstrated that NIRS can be extremely useful in the analysis of the large sample sets required for spatial mapping studies.


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