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Reducing phosphorus losses from agricultural fields: Developing solutions for Ontario Farmers

Principal Investigator: Merrin Macrae

Research Institution: University of Waterloo

Timeline: October 2018 – April 2021  


  • Synthesize edge-of-field runoff (surface and/or tile drainage) and P concentrations and loadings (soluble reactive P (SRP), total P (TP)) results from 8 sites in Ontario (ranging in soil texture and topography) to generate information regarding annual edge of field losses (3 sites), cover crops (2 sites), tillage (3 sites), P application strategies (3 sites) and preferential transport into tile drains (2 sites).
  • Support the development and validation of Phosphorus Loss Assessment Tool for Ontario (PLATO) by providing relevant Ontario-specific information from the data set developed (for the above objective) as well as plot and lab results to address areas of weakness in the tool.
  • Collaborate with farming organizations to educate Ontario farmers, certified crop advisors and other agri-environmental professionals on P transport.


  • Compilation of edge-of-field findings from Ontario sites will shed light on regional differences between Ontario and areas in the USA and improve knowledge on the mechanisms driving these differences.
  • Ontario edge of field data will help to develop and validate PLATO.
  • PLATO will allow producers and agricultural organizations to estimate benefits of practices and demonstrate progress towards P loss reduction on their farms.
  • Public presentations to farmers regarding edge of field research and PLATO will increase adoption of BMPs, reduce mixed messages to farmers and increase acceptance of the PLATO tool.

Scientific Summary:

Agricultural phosphorus (P) losses are a significant economic and environmental concern in Ontario and throughout the Great Lakes Region, particularly in the Lake Erie watershed. Designing and implementing effective best management strategies (BMPs) to reduce P in runoff requires understanding of P loss pathways (i.e., surface versus tile), the form of P (particulate versus dissolved), availability of soil P, and timing of P loss (e.g., seasonality, time since P application). Grain production in Ontario is located on variable soil textures (loam-textured and clay textured) and topography (hummocky till moraines and flat clay-plain), which may result in regionally-specific water and P loss patterns currently not well constrained. Ontario farmers are looking at research and media reports from the USA for guidelines on how to manage P on their farms; however, some of the information may not be applicable to their farms. Thus, there is a clear need to integrate how, why and when P leaves fields across Ontario. This is essential to improve risk assessments and to recommend appropriate BMPs to mitigate P losses across the province.

The goal of this project is to synthesize P loss data (concentrations, loadings and P form) in surface runoff and tile drainage from Ontario croplands (corn-soy-wheat) ranging in soil-texture and topography. This Ontario data synthesis will involve generating seasonal and annual water and P budgets from our edge-of-field long-term water quality monitoring stations (2011-present). Currently no such synthesis of Ontario specific data exists in the scientific literature. This dataset will be used to assist with the development and validation of OMAFRA’s Phosphorus Loss Assessment Tool for Ontario (PLATO).  This tool will be a decision support system for farmers, that quantifies the risk of elevated P loss from their farms based on site specific conditions and management practices. Communication of project outcomes will include oral and written platforms targeting applied users of this data (e.g., Ontario farmers, conservation authorities, OMAFRA). This will include hosting and participating in public outreach events and media programs, as well as contributing to the academic community through peer-reviewed publications and scientific conferences.

External Funding Partners:

Fertilizer Canada

This project was funded in part by the Canadian Agricultural Partnership, a five-year federal-provincial-territorial initiative.

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