Phosphorus mobilization in artificially drained 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 and nuisance algal blooms have been observed in lakes with increasing frequency. Despite the implementation of conservation practices to reduce P loss, P loads are not decreasing and are increasing in some regions. Some of the accelerated losses of P have been linked to the artificial (tile) drainage of agricultural lands, which can rapidly deliver nutrients from recently applied fertilizers as well as legacy stores in the landscape. With the anticipated intensification of the hydrological cycle under a changing climate, tile drainage is expanding throughout North America. Our current conceptual understanding of P mobilization in tile drainage is overgeneralized across different landscapes, climates and management scenarios. Thus, a clearer understanding of the risks of nutrient loss associated with tile drainage is needed. The goal of this proposal, and the short-term objective of my research program is to improve scientific understanding of the impacts of tile drainage on P supply and transport processes from agricultural landscapes. Over the next five years, my research team will provide an improved understanding of P mobilization through the unsaturated vadose zone into tile drains (tile scale) and an improved understanding of differences in P mobilization in tile drained fields with contrasting hydrology (ie poor internal drainage with little groundwater interaction vs variable source area hydrology with shallow groundwater interaction). The proposed work will characterize the complexities of P dynamics across a range of landscapes and environmental conditions. Field investigations will be coupled with novel experiments, and a minimum of five graduate students will be trained as part of this work. This program will have significant environmental and economic impacts as it addresses issues related to land management (tile drainage) as well as climate (and climate change), which are relevant to agriculture and food security. This research is based on data-driven field observations and includes the winter period, during which there is a weak understanding of processes and a paucity of data, and therefore addresses a significant knowledge gap. This will provide an innovative understanding of the contributions of tile drainage to P losses, which is important to balance both crop yields and water quality and thus ensure to future food and water security.