Submitted to: Soil Science Society of America Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/8/2008
Publication Date: 11/14/2008
Citation: Olk, D.C. 2008. Improved analyses for soil carbohydrates, amino acids, and phenols: Tools for understanding soil processes. Soil Science Society of America Journal. 72(6):1672-1682. Interpretive Summary: Our ability to identify and measure the quantities of abundant organic compounds in soil has historically been limited by available technology. This deficiency has restricted our ability to understand soil nutrient cycling, soil aggregation, and other soil processes that involve organic compounds. By using and evaluating new approaches for better measurement of soil carbohydrates and nitrogen-containing compounds, especially amino acids, I identified the strengths and weaknesses of the new approaches and suggested useful evaluations and future applications of them. This information will better explain the new approaches to researchers and promote their future use. Researchers will benefit from improved measurements of soil organic compounds and have a better understanding of soil nutrient and water supply.
Technical Abstract: A process-level understanding of soil carbon(C) and nitrogen (N) cycling will be facilitated by precise measurement of biochemical compounds in soil organic matter. This review summarizes some recent developments in analyses for soil carbohydrates, amino compounds (amino acids and amino sugars), and phenols, with emphasis on recently developed analyses for soil carbohydrates and amino compounds involving anion chromatography and pulsed amperometry, a sensitive detection mode that has otherwise not been widely used in soil science. This carbohydrates analysis has become a leading method, with high resolution, sensitivity, and reproducibility. The corresponding amino compound analysis may be incrementally better than the conventional approach by HCl extraction, cation exchange chromatography, ninhydrin derivatization, and detection by visible light absorption. The two amino approaches need more rigorous comparison with regard to extraction efficiency and sensitivity for each amino compound. The pulsed amperometry approach also needs evaluation in a wider range of research settings. A recently developed soil phenols analysis is based on plant biochemistry studies and distinguishes ether-linked phenols (mostly vanillyl and syringyl) from ester-linked phenols (mostly coumaric acid and ferulic acid). Its applications in a limited number of studies linked specific phenols to soil aggregation and C sequestration. It needs calibration with other phenol analyses favored by soil scientists and biogeochemists, and it needs evaluation in a range of research settings. Like the aminos analysis, this distinction of ether- and ester-linked phenols promises to complement existing analyses.