Runoff generation and phosphorus mobilization in agricultural landscapes

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Phosphorus (P) export from non-point sources in agriculture-dominated catchments is a global issue, and a priority area for many regions in Canada, where Harmful Algal Blooms (HABs) have been observed in large lakes with increasing frequency. Despite the implementation of Beneficial Management Practices (BMPs) to reduce P loss, P loads are not decreasing and in fact are increasing in some regions. Existing models for P export and management strategies largely target rainfall event-driven surface runoff and do not effectively address winter processes and the snowmelt period. This period represents a significant gap in our scientific understanding of P mobilization in agricultural regions. In many midlatitude regions globally, the winter period is the dominant annual flux for both runoff and P. Thus, an understanding of the drivers of P loss in winter and early spring is needed. The objective of this proposal, and the short-term objective of my research program is to improve scientific understanding of the impacts of winter conditions on P supply and transport processes, and how these interact to drive P transfer in surface and subsurface runoff. An improved scientific understanding of runoff generation and P mobilization dynamics in both surface and subsurface pathways in agricultural catchments is needed to develop and implement effective strategies that reduce P loads via both of these pathways. An understanding of the role of climate drivers on these processes will also provide insight into how agricultural systems may respond to climate change, if conditions shift from snow-dominated to more precipitation dominated with reduced soil frost as has been projected. Field investigations will be coupled with novel experiments done in the field and in the laboratory at the University of Waterloo, and four graduate students will be trained as part of this work. My proposed research will have significant environmental and economic impacts as it addresses issues related to climate (and climate change) and issues that are relevant to agricultural management (i.e. artificial drainage). Most importantly, this research targets the winter period, and is based on observational field data, and therefore addresses a significant knowledge gap.