Preferential pathways of phosphorus movement from agricultural land to water bodies in the Canadian Great Lakes basin: A predictive tool

Abstract

Allaire, S. E., van Bochove, E., Denault, J.-T., Dadfar, H., Thériault, G., Charles, A. and De Jong, R. 2011. Preferential pathways of phosphorus movement from agricultural land to water bodies in the Canadian Great Lakes basin: A predictive tool. Can. J. Soil Sci. 91: 361–374. Preferential flow processes, such as crack flow (CF), burrow flow (BF), finger flow (FF) and lateral flow (LF) are known as factors enhancing phosphorus (P) transport from agricultural soils to water bodies. The objective of this study was to develop a methodology for predicting the likelihood of preferential flow processes in agricultural soils at the landscape scale and their potential occurrence around the Canadian Great Lakes. The methodology considered climate, soil and crop parameters and a water budget that calculated surface runoff and drainage. Crack flow largely depended upon soil clay content, BF on soil texture and climate, FF on layering in sandy soils and LF on the presence of trees, slope and soil restricting layers. Crack flow had a high likelihood to occur southern Lake Ontario and all around Lake Erie. A high likelihood of FF could be found in the area where CF was low (i.e., in the sandy soils north of Lake Huron and Lake Ontario). Burrow flow had a medium likelihood to occur on Manitoulin Island and close to the shoreline north of Lake Ontario. Medium to high likelihood of lateral flow might occur in the area south of Lake Ontario, west of Toronto in a narrow band towards Lake Huron, and to a lesser extend in a large area northeast of Lake Huron. Lateral flow may transport soluble P in areas where P was previously carried downward by FF from inland (in soils) to surface water bodies. In several areas, tile drainage may transport all forms of P carried downward from the soil surface to the subsurface by CF and BF to lake tributaries. Preferential flow distribution maps could be used as tools for supporting the identification of agricultural lands where management might enhance subsurface processes of P transport toward groundwater or surface water bodies.