Submitted to: Proceedings of the International Conference on Biogeochemistry
Publication Type: Proceedings
Publication Acceptance Date: 12/1/2000
Publication Date: 8/1/2001
Citation: ALVA, A.K., HUANG, B., SAJWAN, K.S., PARAMASIVAM, S. CHARACTERIZATION OF SOIL SOLUTION ALUMINUM IN SPODOSOLS. PROCEEDINGS OF THE SIXTH INTERNATIONAL CONFERENCE ON BIOGEOCHEMISTRY TRACE ELEMENTS, P. 178. 2001. Interpretive Summary: Solubility of aluminum (Al) increases considerably at pH below 5.0. The spodic horizon in Spodosols is generally acidic in pH, with high organic matter content. This horizon restricts the root growth. Three Spodosols were used in this study to sample the top soil and the Spodic horizon for characterization of soil solution Al and evaluation of root growth of soybean seedlings. Reactive Al concentration was measured using Aluminon method at 30 sec. reaction time. This fraction most likely excludes organically complexed monomeric Al, thus, would represent the predominantly toxic forms of monomeric Al. The concentration of reactive Al varied from 27.5 to 62.7 micromolar in the soil solution from the Spodic horizons. The shoot and root growth of Soybean seedlings were lower in the Spodic horizon samples as compared to that in the top soil of the respective soil series. This study demonstrates the growth limiting effects of Spodic horizon in comparison to the top soil.
Technical Abstract: Spodosols have a Spodic horizon which contains high organic matter along with high concentrations of aluminum (Al) and/or iron (Fe). In most cases, plant roots do not grow into the Spodic horizon due to the low pH and high concentration of Al. Aluminum in soil solution can exist as uncomplexed Al3+ species, and complexed with various inorganic and organic ligands. The sum of all these species comprise monomeric Al. The total soluble Al in solution includes both monomeric and polymeric forms. The colorimetric determination (ex: Aluminon) of Al with short reaction time (30 sec) is considered as a measure of monomeric Al excluding organically complexed forms. The term 'Reactive Al' was used to represent this faction. The objective of this study was to characterize soil solution Al and evaluate the differential phytotoxicity of Al in soil solution in surface and Spodic horizon of three major Spodosols from Florida.