Allelopathic substances in ecosystems : Effectiveness of sterile soil components in altering recovery of ferulic acid

Recovery studies were conducted with ferulic acid, a common allelopathic agent, using various soils and soil components. Ferulic acid was placed into sterile soil components (gibbsite, geothite, Georgia kaolin, and Utah bentonite), and different sterile soil materials (from different horizons in the same profile) varying in mineralogy and in organic matter content. The initial concentration of ferulic acid added to the soil materials was 1000 μg/g (5.149 mmol/g). The pH of the soil materials was adjusted and maintained at approximately 4.5 or 7.5. Samples were extracted with 0.03 M EDTA at days, 1, 4, 7, 10, and 13 after addition of ferulic acid. Concentrations of ferulic acid in the extracts were determined with a high performance liquid chromatograph. No breakdown products were detected. Models were developed to describe the recovery of ferulic acid from each soil material and soil component over time. Organic matter was the most active soil component involved in the irreversible retention of ferulic acid. The inorganic soil components were much less active than organic matter but appeared to be similar to each other in activity. Irreversible retention of ferulic acid by soil and soil components was greatest as pH 7.5.