Fertilizers & Pesticides

Composted Soil Proper use of fertilizers and pesticides and proper techniques for recycling leaves and grass clippings help keep storm water clean. 

    • Reusing grass clippings and leaves prevents excessive nutrients from running into waterways.
    • Properly using fertilizers and pesticides assures hazardous chemicals won't enter the storm water system, where they can cause weed growth, kill native plants, or possibly harm and kill wildlife.
    • Composting can create nutrient-rich soil for a garden or flowers. Having a soil test conducted can tell you exactly which fertilizers to use and in what quantity. Limiting use of pesticides will limit the amount that runs off and contaminates the lakes, rivers and streams.


Most Wisconsin lawns don't need added phosphorus. There is plenty of it in the soil already, and additions of phosphorus fertilizer do not improve turf growth. One way phosphorus enters the water is through runoff that comes from lawn fertilizer. The excess just drains into lakes and streams, which leads to algae growth and reduced oxygen levels.

The State Assembly recently passed a ban that would greatly reduce the ability to use fertilizer that contains phosphorus. Most stores already carry zero phosphorus fertilizers in anticipation of the ban. Just look for the middle number. For more information about soil testing, contact your UW Extension office at 920-391-4617 or visit them online.

If you decide to fertilize, remember to do the following:

  • A lawn fertilization program should begin in early October and not the spring.
  • Fall fertilizer applications should be made when the average daily temperature drops to 50 degrees Fahrenheit.
  • Never pour fertilizer down the storm drain.
  • Sweep up excess fertilizer that was spread onto sidewalks, driveways and the street and reapply to the lawn.
  • Use low or zero phosphorus fertilizers.


If you determine a pesticide is necessary, remember:
  • Consider sharing leftovers (in their original containers) with neighbors.
  • Do not apply in the rain (unless specified).
  • Don’t buy more than you need.
  • Never apply on bare ground or near wells, ponds, and streams.
  • Never dump excess pesticides on the ground or into the storm sewer.
  • Only apply what is necessary.
  • Use a Clean Sweep Program to dispose of pesticides and containers properly.
  • When a container is empty, rinse three times (each time pouring into a sink).

Grass Clippings

Grass clippings contain phosphorus, the nutrient that turns lakes green with algae. One bushel of fresh grass clippings can contain 0.1 lbs of phosphorus -- enough to produce 30–50 pounds of algae growth if it finds its way to a lake or river.

What You Can Do

  • Leave grass clippings on the lawn as natural fertilizer.
  • Mix grass clippings with leaves and soil to make a backyard compost pile.
  • Set the lawn mower at a higher setting (over 2.5 inches).
  • Sweep up grass clippings from streets, driveways, sidewalks and other paved areas and return them to the lawn.
Compost Container


  • Clean leaves and debris from the gutters and storm sewer outlets.
  • Compost your leaves into mulch to place around your vegetables and flowers.
  • Follow your community leaf collection policies and schedule.
  • Learn about your community yard waste disposal practices.
  • Mulch leaves in place by making several passes with a power mower. The shredded leaves will provide nutrients back to your lawn.
  • Put a tarp over leaf piles between pick-up times to prevent them from blowing away.
  • Spread leaves in garden beds or under shrubs.

What are the Benefits?

  • Lawns mowed higher are more competitive against weeds.
  • Lawns mowed higher withstand heat stress better, need less watering, and are more resilient, reducing bare spots and soil erosion.
  • Leaving grass clippings in place leaves the equivalent of 1 pound of nitrogen per 1,000-square-feet, the same amount you would get from 1 fertilizer application.
  • Use of fertilizers can be reduced by 30 - 40% or more by leaving grass clipping on the lawn.