Using Phosphorus-free Lawn Fertilizers

In its efforts to protect water quality in this area, the LakeCounty Water Quality Committee is asking all residents in the county to consider using no-phosphorus lawn fertilizer this summer. In this pamplhet we try to answer questions about the use of no-phosphorus fertilizers.

Questions and Answers

¨ Why use lawn fertilizer without phosphorus around lakes or streams?

A: It is estimated that just one pound of phosphorus in the water will produce 500 pounds of blue-green algae. Most soils in Eastern South Dakota naturally provide all the phosphorus your established lawn needs. Much of the phosphorus  (phosphate) you apply actually runs off the lawn before penetrating the soil. That means it gets into the lakes and streams contributing to the blue-green algae bloom and growth of other undesirable aquatic plants.  For this reason, Minnesota now has a statewide ban on the use of lawn fertilizer with phosphorus except on newly seeded lawns and where soil tests show it is needed.

¨ Why use lawn fertilizer without phosphorus in the City of Madison?

A: Rain and lawn sprinklers can cause the excess phosphorus on city lawns to run off into the storm sewer system.  From there it flows into Silver Creek and on into Lake Madison, Round Lake and Brant Lake.  Studies estimate that about 10-13% of the phosphorus flowing into Lake Madison comes from runoff in the City of Madison.

¨ How do I know there’s no phosphorus in my fertilizer?

A: Check the second number on the package formula. 15—0—10, for example, means zero phosphate. The first number is the nitrogen content, the middle number is the phosphorus content and the last number is the potassium content.  Make sure the middle number on the bag is 0 indicating it it phosphorus free.

¨ What if I use a commercial lawn fertilizer service?

A. Ask your applicator service not to use phosphorus on your lawn. If they are unwilling to remove the phosphorus, contact another dealer or consider applying the no-phosphorus fertilizer yourself.

¨ Does my lawn need phosphorus?

A: No. Unless you have a newly seeded lawn most soil provides all the phosphorus your established lawn needs.  If you are in doubt have your lawn tested before adding any phosphorus.

¨ How does phosphorus damage a lake, stream or pond?

A: Phosphorus encourages the blue-green algae bloom that area lakes experience each summer.  Blue-green algae not only stinks but can be toxic to animals and children. When the algae bloom decays it reduces the oxygen in the water and can cause fish kills.  Phosphorus run-off from feed lots, agricultural land and lawns is the main contributor to phosphorus in the lakes. 

¨ What’s the best way to use a phosphorus free fertilizer?

A: Follow the instructions on the package, and, don’t be afraid to use somewhat LESS than is recommended. Many lawns are over-fertilized.

¨ When should I feed my lawn?

A: The best time to fertilize is in May and early June and again in September or early October.

¨ If I want to use  nitrogen, what’s recommended?

A: Apply no more than one pound per 1,000 square feet of turf area during each feeding. In shade, use half that amount. If you allow grass clippings to decompose on your lawn you can eliminate one application of fertilizer as the decaying grass gradually releases nitrogen into the soil. This saves you both money and time and reduces nitrate pollution. Remember, while nitrogen is needed to produce a thick turf, too much nitrogen will only contribute to pollution of the ground and surface water.

¨ What are some other things I can do to make my lawn more lake friendly?

1. Avoid letting fertilizer wash off the turf.

2. Don’t fertilize when the soil is saturated with moisture.

3. Avoid getting fertilizer on driveways, sidewalks and storm drains.

4. Use a mulching mower to leave the grass clippings on the turf.

5. Cut no more than the top third of the grass. Leaving about 3 inches height shades the roots and helps reduce erosion and runoff.

6. Rake and recycle your leaves in the fall.  Don’t let them blow into the lake.

¨ Where can I buy no-phosphorus fertilizer?

A: In Madison you can purchase phosphorus free lawn fertilizer from Campbell Supply, Domestic Seed and Supply, Jones Ace Hardware and Pamida.  The Chester Farm Service and Chester Hardware in Chester also carries it.  .  Classic Lawn in Chester and TruGreen Chemlawn in Sioux Falls are commericial applicators who will use zero-phosphorus if requested. If your favorite store is not listed here, ask the managers to carry it in the future.    (Note: We have discontinued the Zero-P coupons this year as most residents and dealers we talked with felt they were more bother than they were worth. For the few people who used them in past years, we thank you and encourage you to continue to use Zero-P fertilizer in the future.)

For more information contact:

Lake County Water Quality Committee: (605) 483-3499

SDSU Cooperative Extension Service, Brookings, SD (605) 688-5141