Soil School: Keeping phosphorus on your farm


Are Ontario farmers doing a better job of getting phosphorus to stay put on their farms?

Over the past decade, farmers, agronomists, researchers and governments have ramped up efforts to reduce the amount of phosphorus leaving farm fields and creating environmental challenges in areas such as the Lake Erie and Sainte-Claire watersheds.

University of Waterloo geography and environmental management professor Merrin Macrae believes stakeholders have learned a lot about phosphorus management over the past decade and are “definitely doing a better job.” On this episode of RealAgriculture’s Soil School, Macrae shares research insights compiled over 1o years and how they have shaped best management practices for farmers.

Much of the research has focused on how phosphorus leaves the farm, and how farmers can mitigate nutrient loss from surface run-off and subsurface run-off through tile drains; only 20 percent of field run-off leaves on the surface, while 80 percent exits through the sub-surface in tiles that flow year-round.

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Macrae explains that the amount of applied phosphorus that actually contributes to the nutrient profile and crop growth depends on where you farm in the province, topography, and soil types. For silt and clay loam soils, typically found in midwestern Ontario, nutrient run-off primarily takes place at the surface.

Further to the southwest, in what is often referred to as the clay plain of Essex County, tile drainage plays a much bigger role in the phosphorus movement story. In this region, about 80 per cent of the nutrient leaves the field through tiles.

In the video, Macrae discuses recommended best management practices (BMPs), from sub-surface placement to application timing and cover crops, that farmers are effectively utilizing to reduce the amount of phosphorus flowing through tiles. She believes effective nutrient management plans based on the 4Rs — right source, rate, time, and place — will be key to farmers’ success.

Macrae also believes stakeholders will have to tackle barriers to adoption that have prevented some farmers from embracing phosphorus BMPs. “What is preventing people from taking these steps… What do we need to put in place to help people adopt these BMPs?” she asks.

Click here for more Soil School episodes.

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