Submitted to: International Symposium on Environmental Biogeochemistry
Publication Type: Abstract Only
Publication Acceptance Date: June 15, 2009
Publication Date: September 14, 2009
Citation: Dao, T.H. 2009. Complementary enzymes activities in organic P mineralization and cycling by phosphohydrolases in soils. P. 96. Proc. 19th International Symposium on Environmental Biogeochemistry, Sep. 14-18, 2009, Hamburg, Germany.
Inorganic and organic phosphates react strongly with soil constituents, resulting in relatively low concentrations of soluble phosphates in the soil solution. Multiple competing reactions control the solution-phase concentration and the cycling of phosphorus-containing organic substrates and the released phosphate for assimilation by microorganisms and plants, or their dispersal in the environment. As plants can only acquire phosphorus (P) as inorganic phosphate, recycling of P occurs through the turnover of biological tissues and the mineralization of organic P in its environment. The process is mediated by phosphohydrolases released by microbial systems, plant roots, or arbuscular mycorrhizal associations. So are other catabolic enzymes. As P occurs in biological macromolecules along with carbon (C) and nitrogen (N), incubation and extraction studies were conducted with phosphohydrolases and enzymes of the C and N cycles to determine the potential availability of soil organic P forms in two soils in a temperate climatic zone (i.e., Typic Paleudults and Typic Hapludults). While phosphohydrolases were primarily responsible for the dephosphorylation of soil organic P, the combination of glucosidases, proteases, and peroxidases were complementary and improved the accessibility of P substrates. In regions of intensive animal production agriculture, repeated land loading of animal manure at high rates has led to organic P-enriched soils and a high carbon environment favorable for microbially-mediated catabolic processes. Ligand mediation was also found to have a crucial role in substrate desorption and along with complementary enzymes’ activity enhanced the dephosphorylation of P-containing organic compounds. A ligand-based biological tool was developed and used in assessing the turnover of environmental inorganic and organic phosphates. Therefore, the solubilization of organic P, a forerunner process is crucial to the function of extracellular phosphohydrolases in accessing the recalcitrant soil organic P pool. From an environmental standpoint, the contribution of biologically mediated processes to organic P release and movement must be fully understood to develop sustainable nutrient management practices for our agricultural production systems and mitigate eutrophic responses in environmentally sensitive aquatic ecosystems.