Spring Meltdown: Where Will Nutrients Go?

After a few dry years the abundant amount of snow is more than welcomed this year. Come spring, soil moisture levels will be off to a good start. Along with the extra moisture comes the question, “Where will the soil nutrients go?” This depends on soil conditions prior to the winter’s snowfall. There are two things that could happen, infiltration or runoff.

Figure 1. Runoff from a field during spring meltdown

Infiltration occurs when a snowfall comes before the ground fully freezes in early winter. The snow will insulate the ground preventing it from completely freezing, resulting in a shallow frostline. Come spring the ground will thaw quickly and the moisture from the melting snow is able to be absorbed into the soil. When a large amount of moisture filtered into the soil it can carry the nutrients further down where it is no longer accessible to plant roots. This is called nutrient leaching. Infiltration may not be as worrisome this year considering Saskatchewan has experienced dry conditions in the last few years. The soil has more potential moisture capacity since there was low existing soil moisture going into the winter. This means the existing soil nutrients may not travel far past the first layers.

Figure 2. Effect of timing of first major snowfall on runoff (Government of Alberta)

Runoff occurs when the snow melts quickly before the ground is thawed below the soil surface. The water has no place to go so it will flow into low-lying areas. As it flows it will carry nutrients and organic matter from the soil surface from high areas into the low spots. This erosion can cause eroded knolls and salinity. This is where we often see zones 7-10 higher in nitrogen, sulfur, and organic matter and zones 1-4 tend to be lower depending on the severity of the erosion. Infiltration cannot be prevented; however, soil sampling can help identify the nutrient losses. Using VR can target these zones to help bring these nutrient levels back up to optimize yield.

Figure 3. Showing direction of water flow paths and drainage on a SWAT MAP

Infiltration and runoff can both cause losses. It is important to soil sample and do a proper VR assessment to be able to identify these areas and make adjustments accordingly to ensure all field zones maintain optimal nutrients. Applying more fertilizer where it is needed and cutting back where levels are already sufficient can save money and set you up for better yields. Fields with poor drainage topography can be mapped with SWAT MAPS to help make a proper drainage plan and reduce the negative effects of a heavy spring runoff.

Jaelyn Ford

MAPS and Weather Station Technician

Jaelyn@swatmaps.com