Nutrient Export from Agricultural Watersheds in Ontario Then and Now - A Comparison Across 40 Years

Session: 42. - Multi-Watershed Nutrient Study: Establishing a Monitoring Network in Agricultural Regions

Meguel Yousif, University of Windsor, Mayousif@edu.uwaterloo.ca
Mohamed Mohamed, Ontario Ministry of the Environment and Climate Change, Mohamed.Mohamed2@ontario.ca
Chris Parsons, University of Waterloo, chris.parsons85@gmail.com
Ryan Sorichetti, Ontario Ministry of the Environment and Climate Change, ryan.sorichetti@ontario.ca
Janis Thomas, Ont. Ministry of Environment & Climate Change, janis.thomas@ontario.ca
Christopher Wellen, Ryerson University, christopher.wellen@ryerson.ca

Abstract

The resurgence of eutrophication in the Laurentian Great Lakes along with changes in agricultural land management over decades has led to increasing interest in nutrient export from agricultural non-point sources. Here, we report on a preliminary comparison from two studies in which the same small, agricultural watersheds were intensively monitored; the Pollution from Land Use Activities Reference Group Program (PLUARG, 1975-77) and the Multi-Watershed Nutrient Study (MWNS, 2015-17). We examined both growing and non-growing season nutrient losses, noting some dramatic changes in export. For example, nitrate export increased 4x in the growing season and 2x in the non-growing season at one watershed. However, the only consistent pattern we noted across watersheds and seasons was a reduction in total kjeldahl nitrogen (TKN) export, which was not reflected consistently in other N species. Changes in total and dissolved P were generally small, with a notable increase in dissolved P in only one of the watersheds during the non-growing season. We discuss the potential drivers and implications of these patterns, and future work to connect changes in land management to the observed changes in export.

1. Keyword
nutrients

2. Keyword
water quality

3. Keyword
watersheds

4. Additional Keyword
phosphorus

5. Additional Keyword
nitrogen

6. Additional Keyword
export