Characterization of organic phosphorus in leachate from a grassland soil |
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Authors: | Gurpal S Toor Leo M CondronHong J Di Keith C CameronBarbara J Cade-Menun |
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Institution: | a Department of Plant and Soil Sciences, University of Delaware, Newark, DE 19716-2170, USA b Centre for Soil and Environmental Quality, Lincoln University, P.O. Box 84, Canterbury, New Zealand c Geological and Environmental Sciences, Stanford University, CA 94305-2115, USA |
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Abstract: | The degree of eutrophication in fresh water ecosystems may be influenced by the forms of phosphorus (P) leached from agricultural systems. Physico-chemical fractionation of P in leachate from a grassland soil carried out over a two year period indicated that the majority of the P loss from the Lismore soil occurred in unreactive particulate (55-76%) P forms. 31P nuclear magnetic resonance analysis of a selected leachate sample indicated that unreactive P was mainly comprised of monoester and diester forms of organic P. The presence of phosphomonoesterase (20-200 μg p nitrophenol l−1 h−1) and phosphodiesterase (68 μg bis-p nitrophenol l−1 h−1) activity in leachate resulted in hydrolysis of 10-21% of total unreactive P (TUP), indicating that some of the monoesters and diesters can be eventually hydrolyzed into inorganic P forms during P transport. Enzyme hydrolysis showed that 23% of the TUP was present as labile monoester P (LMP), followed by 20% as inositol hexakisphosphate (IHP) and 14% as diesters (phospholipids and nucleic acids). The findings of this study suggest that LMP, IHP and diesters are an important component of organic P leaching from the grassland soil. |
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Keywords: | Nuclear magnetic resonance Phosphatases Organic P forms Leachate Water quality |
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