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Reducing Phosphorus in Lake Erie

Phosphorus is an essential nutrient for plant life, however, scientists have identified that too much phosphorus is causing increasing growth of toxic and nuisance algae in Lake Erie. Phosphorus can find its way to Lake Erie from many sources, including runoff from agricultural land, which is why Canada and the US have committed to a 40% phosphorus reduction by 2025. Agriculture and Agri-Food Canada (AAFC) scientists have been studying how phosphorus move and change in soil in order to increase use efficiency and reduce loss on farms through runoff.

During the past 20 years, the AAFC team in Harrow has improved our understanding and management of legacy phosphorus, which is the amount remaining in soil after harvest. They found that phosphorus is more available on agricultural lands than previously thought.

They also discovered that the levels of phosphorus available to crops in animal manures are different depending on type and form of the manure. For example, phosphorus in poultry manure is only 25% as available whereas phosphorus in pig manure is 110% as available as the same quantity of phosphorus in commercial fertilizer. This is why the team developed a universal method to determine optimum manure application rates for Ontario soils based on how much phosphorus is available in the manure type.

Tile drainage, which is used in the Lake Erie basin to remove excessive soil water from below the surface and improve crop yields, can also remove valuable phosphorus from fields. The Harrow team developed a drainage water management system that captures and stores the excess water and returns it to crops during dry periods. Recent studies show that used in combination with cover crops, this system can reduce phosphorus loss to adjacent waterways by 23%.

The scientists' methods to predict soil phosphorus losses are now a requirement of Ontario's Nutrient Management Act to help farmers identify fields that need phosphorus-reduction. The team continues to develop innovative technologies to promote crop production and improve surface water quality using the long-term research plots with a state-of-the-art water quality facility.

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