Are current phosphorus risk indicators useful to predict the quality of surface waters in southern manitoba, Canada?
Many phosphorus (P) risk indicators have been developed to assess the risk of P loss from agricultural land to surface water. Most of these indicators are designed for land and climates where rainfall-induced erosion of particulate P from sloping landscapes is the main process of P transport. No indicators have been validated in the Canadian Prairies, where P losses are driven by snowmelt-driven runoff over nearly level landscapes and frozen soils. The objective of this project was to evaluate the relationship between water quality data for P from 14 watersheds and three existing P risk indicators for their potential use in the southern Manitoba prairie region of Canada. None of the indicators, including Birr and Mulla's P Index, a preliminary P risk indicator for Manitoba, and a preliminary version of Canada's National Indicator of Risk of Water Contamination by Phosphorus, was significantly correlated with mean concentrations of total P in water or P export per hectare. Although erosion risk was a significant factor influencing the value of these indexes, erosion risk was not correlated with either measure of P loss in these watersheds. Several other watershed characteristics, including average soil test P concentrations, livestock density, proportion of land in annual crops, and the land's inherent capability for agricultural production, were strongly correlated with P concentrations in water (r = 0.80***, r = 0.63**, 0.76***, and -0.70**, respectively). Therefore, these types of P risk indicators require modifications to estimate the risk of P loss under the soil, landscape, and climatic conditions of southern Manitoba.
Salvano
Esther
E
Dep. of Soil Science, Univ. of Manitoba, Winnipeg, MB, Canada R3T 2N2.
Flaten
Don N
DN
Rousseau
Alain N
AN
Quilbe
Renaud
R
D008350:Manitoba; D010758:Phosphorus / Q000032:analysis*; D018570:Risk Assessment; D014867:Water / Q000737:chemistry*; D014876:Water Pollution / Q000032:analysis*; D014881:Water Supply
D014867:Water; D010758:Phosphorus