Potential for P Release in Streambank Soils of Different Land Uses in the Missisquoi River (Vermont, USA).

The growth of algae blooms in Lake Champlain –located in between the states of Vermont and New York in the United States and the province of Québec in Canada– during the summer months is limited mainly by phosphorus (P). Erosion of streambank soils has been found to be a large source of P inputs entering the Missisquoi River and its tributaries, ultimately discharging it into the lake. In this work, we characterized the P of soils from four different land uses along the Missisquoi River and their corresponding streambanks: silage corn, hay meadow, wetland and forest. We measured total phosphorus, plant-available phosphorus and the degree of phosphorus saturation (DPS). The latter two measurements are predictors of potential bioavailability. Forest soils were low in total phosphorus when compared to the average P content in Vermont soils; while soils in corn, hay and wetland were elevated in total P. With the exception of forest streambank soils, the total P of the corresponding streambanks of each land use was statistically significantly lower. Plant-available phosphorus was very low in forest, wetlands, and all the streambanks of the different land uses; while higher than the optimum plant available P recommended for soils in Vermont in corn and hay fields. The DPS averaged 36% in the corn fields, but was less than 21% in all of the streambanks. The combination of low plant available P and low saturation suggests that the streambank soils will not release significant amounts of P if eroded into the adjacent streams.