ARS | Publication request: Spectral Characterization of Plant-Derived Dissolved Organic Matter

Submitted to: International Humic Substances Society Conference
Publication Type: Proceedings/Symposium
Publication Acceptance Date: May 1, 2008
Publication Date: September 14, 2008
Citation: He, Z., Mao, J., Honeycutt, C.W., Ohno, T., Hunt, J.F., Cade-Menun, B.J. 2008. Spectral Characterization of Plant-Derived Dissolved Organic Matter. International Humic Substances Society Conference. From molecular understanding to innovative applications of humic substances, Vol. I. Humus Sapiens, Moscow, Russia.

Technical Abstract: Dissolved organic matter (DOM) derived from fresh or early-stage decomposing soil amendment materials may play an important role in the process of organic matter accumulation. The DOM can influence many chemical processes, due to its reactivity with both soil solution components and soil surfaces. We characterized seven plant-derived DOM sources with Fourier-transform infrared (FT-IR), solution 31P nuclear magnetic resonance (NMR), and solid state 13C NMR spectroscopies. Solution 31P NMR spectra indicated that DOM samples extracted from alfalfa, corn and soybean shoots contained both orthophosphate and monoester P. Of the monoester P in DOM from soybean shoot, 70% was phytate P. DOM from crimson clover, hairy vetch, lupin, and wheat shoots contained orthophosphate only. FT-IR spectra of the plant-derived DOM were typical for natural organic matter. In the spectra of alfalfa and wheat DOM, the bands at 1400 cm-1 were broad and strong, suggesting these two DOM sources contain more aliphatic and/or phenolic groups. The solid-state 13C NMR spectra of the seven plant-derived DOM samples can be classified into three groups. The spectral characteristics indicated that these DOM sources were primarily composed of soluble carbohydrates and certain soluble organic acids, amino acids, peptides, and phenolic compounds. Structural information obtained from this study may be useful for understanding the effects of DOM on soil nutrient availability to plants.