How can nutrient transport occur? I thought there was no runoff in the prairies.
Snowmelt is a crucial period of nutrient transport. In the prairies, most of the runoff tends to occur in snowmelt. This means we can see most of the nutrients moving in a period of a few weeks or less. Nutrient concentrations at this time can be extremely high — leading to major water quality problems.
Multi-day rainfall events can lead to large amounts of runoff and nutrient transport. Although the growing season is sufficiently dry in many years, we see little or no rainfall-runoff. We are seeing increased multi-day rainfall events in some areas, which can lead to extremely high runoff and nutrient loading.
Key messages: Nutrients can create major issues in downstream lakes in any season. So, even though we often see our ditches dry — short periods of high flow are really important periods of nutrient transport from fields to lakes. We need to manage our agricultural systems to keep nutrients on the land and minimize transport to the water.
Can we manage both agricultural production and water quality?
We need solutions to high nutrient exports that suit our agricultural production systems and our environment. Solutions have to be pragmatic — they have to be workable for producers. Fortunately, many solutions do work — both for producers and for water quality.
- Many new opportunities are coming online, such as variable rate, which allows us to avoid low spots that may have a high risk of nutrient transport.
- We’re also working on understanding when we should consider tilling in low-tillage systems to reduce the stratification of phosphorus in soils.
Key advice includes:
- Carefully managing nutrient inputs, which can save money and reduce runoff, don’t broadcast fertilizers, and don’t fall apply manure.
- If you’re considering water management to drain wetlands — make sure you are aware of the impacts on nutrient transport and how we might mitigate them.
Key message: In all cases, we need local knowledge, and of course, we need to maintain agricultural production. By knowing our land and keeping water quality in mind, there are many pragmatic, economic, and workable solutions.
I see high concentrations of soil nutrients around wetlands. Won’t removing those wetlands help water quality?
Wetlands have a natural role in trapping nutrients and limiting downstream transport. They can be very important sites of nitrogen removal and can retain particles with phosphorus. This can lead to phosphorus accumulation in wetland areas. Without wetlands, we lose important nutrient trapping capacity in the landscape as these nutrients can simply move downstream. With wetlands, we can see these areas where phosphorus may be higher, but it doesn’t mean they have a negative impact on water quality.
Key message: Wetlands are natural features of the landscape. As noted, they can retain nutrients. In the prairies, wetlands have an important function in retaining water — which further strengthens their importance in controlling downstream nutrient transport.
What beneficial management practices work in the prairies? What doesn’t work?
We know the prairies create special challenges to nutrient management, but by knowing our landscape and performing targeted research often in cooperation with producers, we have gained more insight into how to solve our nutrient management problems.
In this article (figures 5 & 6), we provide some summaries about what can work.
If we incorporate new science and broader lessons, we’d recommend:
Red light — stop these practices wherever possible:
- Winter manure application.
- Winter bale grazing unless practiced in conjunction with transport control to prevent runoff.
- Broadcasting fertilizers.
Orange light — areas where we can improve practices include:
- Wet and the low-lying regions near waterways: Consider setbacks and altered phosphorus management in regions with high connectivity to water.
- Drainage: Drainage increases nutrient transport. Minimizing drainage, managing water flows, and limiting nutrient transport are important to mitigate any effects of drainage.
- Conservation tillage: Consider soil testing to understand soil stratification, and consider intermittent tillage should be performed.
- Cover crops: The introduction of cover crops into areas of the prairies is a water quality concern. While these crops can have agronomic benefits, it is important to know that the tissue residues can be major sources of nutrients, which are frequently lost to snowpacks and transported downstream.
Great practices to continue supporting are:
4R nutrient management: this is the single most important option for managing water quality in our agricultural landscape. Within this, soil testing, and considering both agronomic and environmental aspects of input rates is crucial.
Wetland protection and restoration, along with use of small reservoirs.