Submitted to: International Humic Substances Society Conference
Publication Type: Abstract Only
Publication Acceptance Date: 9/1/1998
Publication Date: N/A
Technical Abstract: Runoff from agriculture lands often results in significant losses of soil productivity, and also creates potential water quality problems due to eroded sediments or transport of contaminants (heavy metals and pesticides) in the aqueous phase and/or sorbed to dispersed colloids. In order to estimate the influence of soil management on erosion and contaminant loss, quantitative measurement and characterization of soil organic colloids is essential. The organic carbon content in runoff aqueous phase and sediments as affected by long-term tillage management (no-tillage and conventional- tillage) were studied on a loessial soil grown to soybean. Higher concentrations of organic carbon were measured in runoff sediments and in solution from no-tillage than from convention-tillage soil. We formulated an objective to characterize and quantify humic substance fractions isolated from the loessial soil by sequential extraction based on solubility at various pHs. Surface samples were collected from both conventional- and no-tillage soils; samples were collected from in-row and furrow locations for the conventional-till soil. The soils were exhaustively extracted with the following extractants: i) distilled-water; ii) NaOH at pH 7; iii) Na-pyrophosphate at pH 10.6; and iv) NaOH + Na- pyrophosphate at pH 12.6. The extracted humics were fractionated into humic and fulvic acids and purified using DAX-8 and ion-exchange resins. Results of the quantities isolated and functional groups as determined by 1H-NMR spectroscopy, will be presented.