2025 JOHN OGILVIE RESEARCH INNOVATION AWARDS

“Development of RZWQM2-P model for reducing phosphorus loading from agricultural field to surface water bodies” by Zhiming Qi

Agricultural soils in the humid temperate regions of Canada—particularly in Ontario and Quebec—are a major source of non-point phosphorus (P) pollution in freshwater rivers and lakes, especially when treated with chemical fertilizers, manures, or biosolids. Over the past several decades, the frequency and severity of cyanobacterial blooms have increased significantly. These blooms, along with broader eutrophication issues in freshwater bodies, have been closely linked to the enrichment of phosphorus (P) and nitrogen (N) via subsurface drainage effluent. Subsurface drainage systems are a primary pathway for P transport from agricultural fields in these regions. In response, various strategies have been developed to manage agricultural practices and mitigate P pollution. Among these strategies is the development of computer models capable of simulating and assessing P loss from agricultural lands. Although some models have been updated or newly developed, most lack integration of field management practices and crop growth dynamics, limiting their effectiveness as decision-support tools. Moreover, none currently simulate both dissolved and particulate P losses through subsurface drains simultaneously. To address these limitations, a new phosphorus management tool—RZWQM2-P—was developed. This tool builds upon the Root Zone Water Quality Model 2 (RZWQM2) by incorporating the latest scientific advances in soil and water phosphorus dynamics, while leveraging the model’s existing hydrologic and agricultural management capabilities. The performance of RZWQM2-P was evaluated using data from tile-drained agricultural fields treated with both organic and inorganic phosphorus sources across the Lake Erie watershed (encompassing Ontario, Ohio, and Michigan). Results showed that the model reliably simulated monthly dissolved reactive P and total P losses via surface runoff and tile drainage, achieving a Nash-Sutcliffe efficiency coefficient greater than 0.35, percent bias within ±25%, and an index of agreement exceeding 0.75 across the study sites. RZWQM2-P represents a promising advancement in phosphorus management, particularly for subsurface-drained agricultural systems.