Evaluation of agricultural phosphorus losses by runoff, drainage and leaching in a Quebec context: application of the LoPhos tool

Abstract

Often neglected until now in the environmental budget of agricultural activities, phosphorus more and more appears as a potential important contaminant as well for the surface water as for ground water. Easily and rapidly adsorbed by clay particles, phosphorus wasn't very found in water resources despite application rates sometimes excessive, such as with liquid manure spreading. However, because a continuous and significant spreading on sometimes limited agricultural areas, a saturation of soil can be reached and losses of phosphorus may then be as large as the application rate. For that, Quebec has developed innovative techniques to quantify and survey the phosphorus soil saturation. Among them, LoPhos is a tool that evaluates the phosphorus losses over an agricultural farm from easily available data. An application of this tool on a watershed of Quebec is presented in this paper showing the importance of the soil saturation and the impact of best management practices. The transposition in France of the knowledge developed in Quebec and such tool like LoPhos offer interesting perspectives when appears at present a phosphorus problematic related to the spreading of farming effluents.