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Flushing phosphorus down the drain tile?

TAGS: Conservation
leightrail/Getty Images Farmer seeding corn next to wind farm
RECONSIDER NO-TILL: Stopping the practice of no-till to prevent phosphorus loss in tile is not always the answer, warns Merrin Macrae of the University of Waterloo in Ontario.
Learn more about practices to keep phosphorus in your field and out of the water.

Sometimes we get wrapped up in borders, but water doesn’t honor these boundaries. Our neighbors in Canada have been great partners in the research and application of nutrient reductions to help with the cleanup of Lake Erie from harmful algal blooms.

Merrin Macrae of the University of Waterloo in Ontario recently joined Michigan State University Extension educators on the “In the Weeds” podcast to discuss nutrient losses in field crops.

Cover crops can help hold on to nutrients

Macrae specializes in water quality in the Great Lakes, and specifically the impacts of agriculture on water quality. She recommends the use of cover crops to hold soil in place and to prevent phosphorus from running off in sediment. This is in line with the recommendations of the MSU Extension Cover Crop Team and the Midwest Cover Crop Council.

Concerns have been raised that phosphorus loss occurs during the winter when cover crops freeze and thaw, contributing to water quality issues. Macrae clarifies the freeze-and-thaw cycles in the Great Lakes are not as severe as in the prairie where research has shown the freeze-thaw cycle to be an issue with cover crops.

The Great Lakes region also has ample snow cover, a factor that protects cover crops. She suggests phosphorus loss can be reduced by using more hardy cover crops such as rye and vetch. Leaching also is greater where cover crops are waterlogged, so providing proper drainage, or avoiding planting cover crops where it floods each year in the field, can help prevent this.

Smart trade-offs

Stopping the practice of no-till to prevent loss in tile is not always the answer, Macrae warns. Tillage can mix your soil, preventing nutrient stratification and leaching through macropores, but it also promotes erosion. Consider where you farm and each field’s unique properties.

If you have rolling topography and lighter soils, most of your phosphorus loss may be from surface runoff, so no-till and cover crops would be great practices to implement. Alternatively, if you farm where there are heavier soils and flat lands, your loss may be through tile drains, so different cover crops and reduced tillage may be in order. Choose the best practices to prevent nutrient loss based on your soil types.   

Wacky weather

The Great Lakes region should expect to have more extreme rain events because of climate change. These large events spike phosphorus in our waterways and spur flooding across the watershed. They also postpone field practices and cost money to repair fields and replace applications of nutrients.

Adapting your farm practices now can help you deal with flooding in the future. Conservation practices and using the 4Rs — in particular, the right rate and right place — are critical in creating a resilient cropping system.


It is important to manage for both surface and subsurface phosphorus loss. Get the fertilizer underground. By putting the fertilizer underground in a band, losses can be reduced from 70% to 90%.

Be precise with your management. Select cover crops, tillage practices, nutrient rates and placement based on your field’s soil type and topography.

Fronczak and Jean are MSU Extension educators.

Source: MSU Extension, which is solely responsible for the information provided and is wholly owned by the source. Informa Business Media and all its subsidiaries are not responsible for any of the content contained in this information asset.
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