Nutrient Loss From Saskatchewan Cropland and Pasture: Comparing Runoff From Spring Snowmelt and Summer Storms.

Nutrient loss from agriculture can significantly reduce downstream water quality and trigger harmful algal blooms.  In the Canadian prairies, the majority of nutrient loss from agricultural lands occurs as surface runoff during spring snowmelt events, while the ground is still frozen.  Summer storms that trigger runoff are relatively infrequent in this region.  Nutrient loss during snowmelt runoff is predominantly in dissolved form.  In contrast, summer storm runoff is more erosive, and more nutrients are lost in particulate form.  In agreement with regional climate models, moisture conditions have been drier than normal for the past decade (9% below average).  However, higher intensity rainfall events are in evidence. These high intensity precipitation events can produce high flow rates that transport particulate nutrients considerable distances. Further, higher than average snowfall accumulation in recent years has produced sufficient snowmelt runoff to significantly transport dissolved nutrients to a greater extent than normal. 

   Climate changes that alter summer storm frequency and intensity, or reduce snowfall and thus snowmelt runoff, have the potential to change the pattern of nutrient loss from agriculture in the Canadian prairies. In order to develop the most appropriate management practices to reduce nutrient loss from agriculture within a watershed, it is essential to quantify the nutrients lost from agricultural fields in different seasons and with different agricultural practices, and to identify the primary mechanisms for this nutrient loss. Seasonal runoff samples have been collected from snowmelt and summer storm runoff in southeastern Saskatchewan since 2010, from annual cropland and permanent pasture.  This presentation will compare the mechanisms (dissolved versus particulate) and chemical forms (ammonium, nitrate, total N, C, phosphate, total P) of nutrients transported from these agricultural practices in various seasons.  This information will allow us to use appropriate management practices and to adapt these practices as needed for climate change.