Fluorescence Spectroscopic Investigation of Tillage, Cropping Management, and Nitrogen Application Effects On Stable and Water-Extractable Organic Matter.

Organic matter (OM) controls many important soil ecosystem processes. Stable (humic and fulvic) and water-extractable OM was obtained from soils in a nine-year tillage, cropping management, and nitrogen application study and characterized for its composition using multi-dimensional fluorescence spectroscopy with parallel factor analysis (PARAFAC). The distribution of component concentrations was unique to each type of organic matter fraction indicating that these operationally extracted fractions reflect differing chemical pools of soil organic matter. Tillage, cropping, and N source application did not affect component distribution of the stable OM fractions; however, the component distribution of the more labile water-extractable organic matter fraction was significantly affected by N source. Our results support the premise that multi-dimensional fluorescence spectroscopy with PARAFAC is a suitable method for monitoring the dynamics and chemical nature of soil organic matter.