This past summer, a “moderately” severe algae bloom grew in beloved Lake Erie. This unwelcome visitor continues to make yearly toxic appearances in the warmer months. When it comes to these toxic algae blooms, even a “mild” or smaller bloom is bad news. These blooms, regardless of size, contain harmful concentrations of microcystin, a potent liver toxin, and possible human carcinogen (cancer-causing substance) produced by certain kinds of algae.

We have a long way to go to address the summer plague of Lake Erie algae blooms, and we also know that the actions required to do so are a year-round job. The application of excess fertilizer is a practice that must end across the agricultural industry, as it is a key contributor to the persistent issue of toxic algae blooms in freshwater ecosystems. 

While some fertilizers are synthetic and full of chemicals (an issue of its own), many farmers’ fields are using animal manure to grow their crops. Using a natural fertilizer such as manure is a good practice, but there are still some rules that need to be followed to minimize negative impacts on the environment. 

This includes fertilizer management best practices such as those known as the “4 Rs.” Applying the right fertilizer source at the right rate, at the right time, and in the right place – are considered the rules of thumb for fertilizer application. These rules apply to manure as well as chemical fertilizers. And when it comes to applying manure, winter is the worst time.  

What are the risks of winter spreading?

Winter spreading of manure (applying fertilizer on frozen or snow-covered ground) is a practice under intense scrutiny because it increases the amount of fertilizer which runs off and seeps into rivers and lakes. This causes pollution and harm to essential water sources.  Frozen soils have little to no infiltration, so immediate runoff occurs if rainfall or snow melts before the soil thaws. There is also the fact that with winter spreading, no growing crops are available to absorb the nutrients from the fertilizer. 

Although winter spreading of fertilizer is actively discouraged within the agricultural community, and by the Ontario Ministry of Agriculture, Food, and Rural Affairs, it still occurs.

One of the main reasons manure is applied in winter is because farmers with livestock are looking for a place to put the animal manure they don’t have space to store. For this reason, increasing manure storage capacity is an obvious way to reduce winter spreading. A more heavy-handed approach taken by some governments is to ban winter spreading altogether to try to enforce full compliance within the farming community. 

What protections exist in Ontario to protect the Great Lakes from agricultural runoff and nutrient pollution? 

Several pieces of legislation exist in Ontario that make it an offence to allow manure to enter waterways. The main pieces of legislation are the Environmental Protection Act, the Ontario Water Resources Act, the Nutrient Management Act, and federally, the Fisheries Act. Farmers are also required to have fertilizer management plans in place for crops and managing animal waste. This includes ensuring enough storage capacity for manure. 

Despite these laws, excess nutrients make their way into the watershed year-round, including in the wintertime. The Nutrient Management Act and its regulations only capture a minority number of farms. Governments are also relying too heavily on education and outreach to ensure that farms self-report whether they meet the conditions set out in the regulations. In the past, it has also been found that in Ontario, the Ministry of Agriculture has not followed up when farms were not following the existing provincial policies set out and rarely took any action such as issuing offence notices that may result in fines set by provincial courts. 

What more needs to be done? 

These weaknesses in the Nutrient Management Act and how well it’s followed are contributing to year-round issues with excess fertilizers reaching water sources including in the winter months. All of this is adding to ongoing stress and lake imbalances which can be observed every summer and early fall with the toxic algae bloom that plagues Lake Erie. To fix this, governments need to strengthen the regulations requiring farms to have nutrient management plans. For the farms that do require plans, the Ministry needs to do a better job of making sure they are following the rules. 

Every year, scientists from NOAA and the Great Lakes region warn us that Lake Erie is approaching a tipping point, and if we don’t get our act together in the near term, we could lose one of our greatest global treasures. Bringing an end to the winter spreading of manure is one of the critical actions we need to take if we want to avoid this devastating loss.