Managing phosphorus for improved water quality: best practices depend on where you farm
Thanks to drier-than-normal spring seasons the past two years, harmful algae blooms in 2020 and 2021 in the western basin of Lake Erie have not been as severe as in preceding years. Phosphorus (P) loading to the lake, however, remains an important issue on both sides of the Canada-US border. Ontario farmers want to do their part to reduce phosphorus losses to water bodies. And as we learn more, it appears that the most effective best management practices (BMPs) may depend on where you farm and the type of land you manage.
Dr. Merrin Macrae, Professor at University of Waterloo, has led multiple on-farm, edge-of-field trials on phosphorus and water quality within the Lake Erie watershed over the past decade. Recently, she pored over the findings and, along with other experts from Ontario and the US, developed regionally specific guidance on phosphorus management. In this crop report we will share some of the highlights.
Phosphorus management regions
Macrae breaks up the Lake Erie watershed into four regions based on climate, topography, elevation and soil characteristics (Figure 1). In the Lake Erie watershed, they include the southwest (SW), northeast (NE) and the transition zone between the two. The SW represents a warmer region with flat, clay-based soil, less snow, and more precipitation as rain. The NE has fewer winter thaws and more snowpack, higher elevation and more topography.
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