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A Tale of Two Cities' Lawn Care Practices

Man walking on water's surface with lawn fertilizing aparatus

The impact of phosphorus on lakes and rivers is gaining attention across the country. As this public education campaign image from the Washington State Water Quality Consortium points out, "When you're fertilizing the lawn, remember you're not just fertilizing the lawn."

Plymouth, MN, like a growing number of Twin Cities suburbs, has an ordinance restricting the use of phosphorus for lawn fertilization. Plymouth's neighboring city, Maple Grove, does not have a phosphorus-restricting ordinance. This sets up an opportunity to compare lawn care practices between homeowners in the two cities and see if the ordinance reduces the phosphorus content of water runoff.

The University of Minnesota Sea Grant Program, the Three Rivers Park District, and the Hennepin Conservation District, are taking advantage of this opportunity by conducting a water quality research project and public education campaign to inform homeowners about environmentally-sound lawn care practices.

The problem is that most soil in that part of Minnesota already has enough phosphorus to produce healthy lawns. After a person fertilizes their lawn, the unused phosphorus doesn't stay in the lawn. It gets washed away by rains, along with leaves and grass clippings, and enters lakes and rivers through stormwater runoff. The added nutrients can degrade water quality and promote the growth of algae leading to the greening of Minnesota's sky blue waters. And with eight major lakes covering 20 percent of the city, Plymouth has a lot of water to worry about (see map).

Map of phosphorus study

Map of study area

The project is wrapping up this year. In spring, 2001, researchers conducted a lawn care survey of homeowners in Plymouth, MN. The surveys were delivered door-to-door by students from Dan Hanka's class at Armstrong High School and David Astin's class at Wayzata High School.

Of the 142 people to respond, 77 percent fertilize their lawns. Of those who fertilize, about 50 percent apply it themselves and 40 percent use a professional lawn service (the other 10 percent had their lawns fertilized by another resident, a landlord, or an association).

"This is interesting because even though most of the people in Plymouth fertilize their lawns themselves, 70 percent don't know or remember how much they applied to their lawns, and even more couldn't tell us the nutrient content of the fertilizer they used," said Barb Peichel, program assistant with Minnesota Sea Grant. "This tells us that we need to let people know it's important to pay attention to their lawn care practices because it can impact the environment."

Only 2 percent of those who fertilize their lawns calculated the quantity they used based on their yard size or soil tests. Most relied on their lawn service or on the recommendations found on fertilizer bags and have never had their soil tested (76 percent).

"We'd like to encourage people to get a simple, inexpensive soil test from their county extension office so that they know what nutrients their lawns actually need," said Peichel, "and to consider using a phosphorus-free fertilizer. Research shows that 70-80 percent of lawns in the Twin Cities region already have enough phosphorus in the soil to be healthy."

Twenty-two percent of surveyed homeowners remove grass clippings every time they mow, and in the process remove an easy way for lawns to self-fertilize. Leaving the clippings on lawns provides nutrients and moisture, and can reduce the amount of fertilizer needed for optimal turf growth. Another simple way to improve a lawn is to aerate it if the soil is compacted. Compaction keeps air, water, and nutrients from entering the soil, and may increase the amount of nutrients that run off lawns.

In addition to the survey, a scientific research project is being conducted within the Maple Grove and Plymouth watersheds to examine differences in phosphorus levels in runoff.

"Preliminary results show there's a 23 percent difference in phosphorus between the cities -- it's lower in Plymouth," said James Johnson, a water quality technician with the Three Rivers District of Hennepin Parks. Johnson is collecting more data this spring to complete the comparison.

These efforts are part of the Lake Access project, a cooperative venture between the institutions already named above and the University of Minnesota Duluth's Natural Resources Research Institute and Education Department. The project is funded by the U.S. Environmental Protection Agency's Environmental Monitoring for Public Access and Community Tracking (EMPACT) program with the goal of making water quality data more publicly available over the Internet.

Full results of the survey and a description of the overall study can be found on the Lake Access Web site, under the "lawn fertilizer experiment" section.

On April 19, Minnesota Governor Jesse Ventura signed a new law that prohibits the use of phosphorus-containing fertilizers on lawns (not on agricultural land) in the Twin Cities metropolitan area. Phosphorus fertilizer can only be used in the seven-county metro area if a soil test conducted within the past three years determines a need for the nutrient. Property owners laying sod for the first time and licensed professionals applying fertilizer on golf courses are exempt.

In the rest of Minnesota, a small amount of phosphorus will be permitted in liquid and granular fertilizers. The restrictions take effect January 1, 2004.

The agriculture commissioner, along with the University of Minnesota Extension Service, the fertilizer industry, and lake groups, are required to provide consumers with best practices information on lawn fertilizers under the law.

Those ignoring the measure would be subject to a petty misdemeanor penalty. House bill sponsor Peggy Leppik (R-Golden Valley) said the goal isn't to punish people, but rather to educate them on the environmental harm caused by phosphorus.

Speaking in support, Shorewood, MN, Mayor Woody Love said that cities throughout the state are concerned about phosphorus and the impact it has on lakes.

"If there is an one-thousand mile journey to protect our water bodies, this represents a significant stride," Love said.

March 1 and April 26, 2002 Session Weekly (a MN House of Representatives nonpartisan publication)

By Marie Zhuikov
June 2002

Return to June 2002 Seiche

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