title: Risk of phosphorus desorption from Canadian agricultural land: 25-year temporal trend.
abstract: Phosphorus (P) use in excess of crop needs may impact surface water quality and contribute to eutrophication. However, P loss from agricultural land to water has never been estimated at the Canadian national scale. In this paper, the risk of P desorption from Canadian agricultural land is assessed by the source component of the indicator of risk of water contamination by P (IROWC-P). The IROWC-P source component (P_source) characterized the mobilization potential of soluble P and integrated four models of P desorption by water for dominant agricultural soil series of Canada on the soil landscape of Canada polygon scale (1:1,000,000). The objective of our study was to describe and evaluate a standardized method for deriving the P_source component. The P_source was assessed over 5-yr intervals from 1981 to 2006 for scientifically based knowledge by relating annual P balance values, soil test P (STP) analyses, soil P saturation index, and Self-Davis water extractable P extraction values. Results show trends of soil P enrichment for most Canadian provinces over the 25-yr period but also an increased percentage of farmland classified above the water extractable soil P environmental threshold of 4 mg P kg. The Canadian Prairies and Ontario showed small P_source values and almost no farmland above the environmental threshold. Quebec and the Atlantic Provinces had P_source values that exceeded the environmental threshold in 2006; more than 33% of farmland is classified above the environmental threshold value.
authors.affiliation: Agriculture and Agri-Food, Canada. eric.vanbochove@agr.gc.ca
authors.forename: Eric
authors.initials: E
authors.lastname: van Bochove
authors.forename: Georges
authors.initials: G
authors.lastname: Thériault
authors.forename: Jean-Thomas
authors.initials: JT
authors.lastname: Denault
authors.forename: Farida
authors.initials: F
authors.lastname: Dechmi
authors.forename: Suzanne E
authors.initials: SE
authors.lastname: Allaire
authors.forename: Alain N
authors.initials: AN
authors.lastname: Rousseau
mesh_terms: D000383:Agriculture / Q000639:trends*; D002170:Canada; D005843:Geography; D010758:Phosphorus / Q000032:analysis*; D012987:Soil / Q000032:analysis*; D014877:Water Pollution, Chemical / Q000032:analysis*
chemical_list: D012987:Soil; D010758:Phosphorus