Lawn Fertilizer And The Health Of Our Lake

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The following is currently contained within the Rules and Ordinances for our lake.

“It is strongly recommended that homeowners refrain from using chemical fertilizers, weed killers, and pesticides on their properties. These chemicals eventually leach into the lake and damage the quality of the water, and can encourage unwanted plant life. Only natural ‘lake friendly’ organic materials in moderate amounts should be utilized.”

Not only chemical lawn fertilizers affect lakes. Any source of excess nutrients, whether chemical or natural, can contribute to a dense growth of plant life and the death of animal life from a lack of oxygen.

1.     Nitrogen (N) and phosphorus (P) from lawn fertilizers wash into lakes through rain or irrigation runoff.

2.     These nutrients fuel excessive growth of algae (algal blooms), especially harmful cyanobacteria (blue-green algae).

3.     Excessive nutrients also reduce oxygen levels for fish.

Best Practices to Reduce Impact:

• Use slow-release or phosphorus-free fertilizers.

• Cut the grass a little higher.  Taller grass supports deeper, stronger root systems, which improve soil structure and infiltration, meaning more water soaks in instead of running off.

• Leaving your lawn clippings improves water infiltration rather than letting it run off. 

• Maintain a buffer strip of native plants between lawns and lakes.

• Avoid fertilizing before rainstorms, which can increase runoff.

• Don’t  fertilize in July and August since grass grows less in the heat. Since the grass is growing less, it isn’t able to take in as much of the fertilizer, which can then easily be picked up by rainwater and washed into lakes and ponds.

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Resources:

CT DEEP Phosphorus Strategy https://portal.ct.gov/-/media/deep/water/water_quality_standards/p/pa12155fullccreportpdf.pdf

CT DEEP information on cyanobacteria (blue-green algae). https://portal.ct.gov/deep/water/water-quality/blue-green-algae-blooms

This is an article that explains the impacts of fertilizers on lakes and how to pick more lake-friendly ones, from the New Hampshire Department of Environmental Services.

Here is a fact sheet from Oklahoma State University.   The article recommends soil testing.  UConn has several options available.

Thanks to Cassidy Plaud,  Outdoor Educator & Program Coordinator, The Last Green Valley, Inc., for providing much of the information included here.

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Thanks to John Barber for his research on fertilizing and its effect on our lake.

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7/1/2025