Preliminary Characterization of Organic Phosphorus Species in Soils Along the Missisquoi River (Vermont, USA).

Erosion of soils can lead to high inputs of phosphorus (P) entering the Missisquoi River and its tributaries, ultimately discharging it into Lake Champlain (located in between the states of Vermont and New York in the United States and the province of Québec in Canada). This contributes to the growth of algae blooms in the lake during the summer months. Little has been documented about the contribution of organic P and its enzyme mediated-bioavailability in stream corridor soils. In this work, we will characterize the organic P (monoester-P and nucleic acid-P) of soils from different land uses along the Missisquoi River, using two acid phosphatases from potato and wheat germ, and Nuclease P1 from P. citrinum. These land uses will include silage corn, hay meadow, wetland and forest. Preliminary results taken along a transect in a hardwood forest, parallel to the streambank, show a large variability between sample sites, ranging from 54 to 372 mg P/kg of soil of monoester-P and 232 to 707 mg P/kg of soil of nucleic acid-P. Inorganic P, readily bioavailable without enzyme intervention, also varies significantly, ranging from 379 to 1014 mg P/kg of soil.  These results will be compared with differences in soil properties, including pH, organic matter and texture. A thorough characterization of the organic P in soils along the river corridor of the Missisquoi River combined with the inorganic P content could be used to more accurately predict bioavailability of P in eroding soils.