THE REFLECTANCE SPECTRA OF ORGANIC-MATTER IN THE VISIBLE NEAR-INFRARED AND SHORT-WAVE INFRARED REGION (400-2500-NM) DURING A CONTROLLED DECOMPOSITION PROCESS

The reflectance spectra of organic matter in the VIR-SWIR regions (400 -2500 nm) were investigated with regard to possible changes that might occur during a biological decomposition process. Two different groups of organic matter were used in this study: a grape marc (CGM) and a s eparated cattle manure (CSM) that simulated pure organic matter endmem bers in soils. Exposing the too materials for different decomposition durations (0-378 days) visually yielded color sequences as the compost aged. Significant changes in the reflectance spectra of both material s were also observed during the composting period, which provided para meters for controlling the composting process. The slopes In the VIS-N IR region were found to be basic parameters for monitoring changes and were found to be highly correlated with other chemical parameters oft en used for assessing organic matter conditions in the field (such as the C/N ratio). It was found that during the initial composting stage (0-60 days) the slope parameters were strongly affected by the decompo sition activity and, hence, errors in the assess ment of organic matte r content of soils. using Slope (or band ratio) parameters are likely. Careful observation of the major spectral features reveals that the r eflectance spectrum in the VIS-NIR-SWIR region is a very sensitive too l for monitoring slight changes. Application of the near-infrared anal ysis (NIRA) pathways revealed that OH and C-H groups combined with hyg roscopic water starch, cellullose, and lignin are the components havin g the highest correlations with composting time within the conditions used. Because of the small number of samples in each testing group a c omplete NIRA employing validation tests could not be carried out. We c onducted that the reflectance spectrum in the VIS-NIR-SWIR region is a promising tool for monitoring the composting process and that the com posting process may provide invaluable spectral information about soil organic matter during its biochemical degradation. (C) Elsevier Scien ce Inc., 1997.