Use Phosphorus-Free Fertilizer to Keep Lawns Green, Waters Clean
Melting snow or a summer rainstorm can quickly wash phosphorus from your fertilizer and other pollutants off your lawn and into our lakes, rivers and bays. Phosphorus is like junk food for algae causing it to grow out of control, turning out waters green, lowering water quality and even killing fish. Even if you live far from the shorefront, all stormwater eventually makes its ways to our waters, with half eventually draining into our lakes and the other half draining in our rivers or bays.
Most soils in Maine naturally have enough phosphorus to keep a lawn lush and green so if you use fertilizer, make sure it is phosphorus-free (noted by the “O” in the middle number describing the fertilizer blend). Only use phosphorus when establishing a new lawn, re-seeding or when recommended by a soil test from a lab.
Rather than ban the sale of lawn fertilizer containing phosphorus as some other states have done, Maine has chosen to empower retailers and educate consumers by requiring stores that sell fertilizer to post signs explaining when it is appropriate to use fertilizers with phosphorus. The law (38 MRSA 419) states:
"A person may not sell fertilizer containing phosphorus at a retail store after January 1, 2008 unless the seller posts a Department of Environmental Protection approved sign that indicates the product is not appropriate for use on non-agricultural lawn or turf due to potential adverse effects on water quality except when:
- Soil test results from a laboratory indicate that additional phosphorus is needed for lawn or turf; or
- The fertilizer will be used in establishing a new lawn or turf, including establishing turf at a sod farm, or for re-seeding or over-seeding existing lawn or turf.”
Questions to Consider
- How much fertilizer should I apply?
- If you must fertilize - avoid over fertilizing! Measure your lawn area to determine the square footage. Then calibrate your spreader to apply one-half the recommended amount of fertilizer based on the bag's label. Watch for lawn response. Reapply at the reduced rate when your lawn's response is not acceptable. More is not better. Don't apply before spring green-up. The best time is September.
- To have a good looking lawn, do I even need to fertilize my lawn?
- No, if you leave your grass clippings (the natural fertilizer) and your lawn is 10 or more years old there are enough nutrients in the soil to grow a healthy lawn. (And clippings don't lead to thatch.) Younger lawns may need nitrogen: look for bags with 10-0-0 on the label.
- How do I find phosphorus-free fertilizers in the store?
- The amount of phosphorus can be located by looking for the three numbers on the package. The numbers indicate the percent of nitrogen, phosphorus and potash. Look for packages where the middle number is zero for phosphorus-free.
- How can I get a soils test done?
- Get your soil test kit at stores that sell fertilizer, University of Maine Cooperative Extension Offices, Soil & Water Conservation Districts and the University of Maine Soil Testing Service.
- Maine Board of Pesticide Control information on lawn care pest control.
- Think Blue Maine homeowner resources on reducing stormwater run-off and pollution prevention
- University of Maine Analytical Lab and Soil Testing Service (207-581-3591)
- YardScaping – Resources for healthy lawns and landscapes from the Maine Department of Agriculture, Conservation and Forestry