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Title: DETERMINATION OF BIOLOGICAL MEASURES BY MID-INFRARED DIFFUSE REFLECTANCE SPECTROSCOPY IN SOILS WITHIN A SMALL TOPOSEQUENCE

Author
item MIMMO, TANJA - DEPT OF CHEM, BOLOGNA, IT
item Reeves Iii, James
item McCarty, Gregory
item GALLETTI, G - DEPT OF CHEM, BOLOGNA, IT

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/2001
Publication Date: 4/1/2002
Citation: MIMMO, T., REEVES III, J.B., MCCARTY, G.W., GALLETTI, G. DETERMINATION OF BIOLOGICAL MEASURES BY MID-INFRARED DIFFUSE REFLECTANCE SPECTROSCOPY IN SOILS WITHIN A SMALL TOPOSEQUENCE. SOIL SCIENCE SOCIETY OF AMERICA JOURNAL. 2002.

Interpretive Summary: Spectroscopy utilizes the interaction of light with materials to determine their composition. The objective of this work was to determine the effects of sample diversity on mid-infrared spectroscopic calibrations (process for relating spectra to compositions) for biological activity in soil. One hundred and thirty six soil samples were taken from a 20 ha field within a small watershed. The samples were obtained in a grid pattern from the top ten centimeters. Samples were analyzed spectroscopically and by conventional methods for total N, total C, and several measures of biological activity. The mid-infrared results for total C, total N and three enzymes were as good as found in previous studies using less diverse sample sets, and were better than achieved using near-infrared spectra for this data set. However, while previous work with a less diverse set of samples had produced promising results for biomass N, determination of biomass C and N, two other measures of biological activity, were not found to be feasible for this set of samples. Overall, while further work is needed, these results indicate that sample diversity is not always detrimental to accurate determination of biological activity in soils when using mid-infrared spectra.

Technical Abstract: The objective of this work was to determine the effects of sample diversity on mid-infrared spectroscopic calibrations for biological activity in soil. One hundred and thirty six soil samples were taken from a 20 ha field consisting of a toposequence within a small watershed. The samples were obtained in a grid pattern from the top ten centimeters. Samples were analyzed spectroscopically and by conventional methods for total N, total C, alkaline and acid phosphatase, arylsulfatase, biomass N and biomass C. Dried and ground samples were scanned in the mid- infrared using a FTIR. Mid-infrared results were an improvement over near-infrared results for total N and C (R2 of approx. 0.85 and .95, resp.)and biological activity as reflected by the three enzymes, but were unsatisfactory for measures of biomass N and C. Overall, the results, based on RMSD/mean, for the three enzymes were as good as found in previous studies using less diverse sample sets and were much better than achieved using near-infrared spectra for this data set.v In conclusion, while further work is needed, these results indicate that sample diversity is not always detrimental to accurate determination of biological activity in soils when using mid-infrared spectra.