In Your Backyard

From Stef '06 at the DEP:

New Fertilizer Law for Our Back Yards

Spring is here and many Mainers are starting to think about getting their lawns in shape. For some that means going to the store to get the first fertilizer of the season. But wait! What kind of fertilizer will help get you a beautiful lawn? Is this the right time to apply fertilizer? Do you even need to buy fertilizer? New research can help you have a healthy lawn with fewer lawn chemicals.
First, most lawns don't need fertilizers containing phosphorus. Over 90% of lawns tested in the past 5 years would not have become greener with additional phosphorus. That means your lawn - and your lawn care budget – shouldn't require phosphorus to stay healthy.
To have a good looking lawn, you may not need to fertilize at all. 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. Even better for your budget! (And by the way, clippings don't lead to thatch.) Younger lawns may need some nitrogen.
So if your lawn doesn't need fertilizer and phosphorus in particular, please don't use it. Save time and money -- and your local waters. Just as fertilizer can help plants grow in your yard, they also can help plants in our lakes, streams, and bays. Rainwater and melting snow wash fertilizers and other pollutants from our lawns down our driveways, road ditches into storm drains or directly into nearby waters. Those fertilizers can turn our waters green, lead to smelly scums, and rob the water of its oxygen causing fish kills.
Lakes and streams are so sensitive to phosphorus that a new law effective January 1, 2008 discourages the use of lawn fertilizers containing phosphorus.
It is ok to use phosphorus fertilizers when:
1. Soil test results from a laboratory indicate that phosphorus is needed or
2. The fertilizer will be used to establish a new lawn, although new research shows that most soils only need nitrogen.
The amount of phosphorus can be located by looking for the 3 numbers on the package label. The numbers indicate the percent of nitrogen, phosphorus and potash, in that order. Look for packages where the middle number is zero for phosphorous free such as 10-0-5.
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 your lawn's response. Reapply at the reduced rate when your lawn's response is not acceptable. Don't apply before spring green-up. If your lawn isn't growing – it can't take up the nutrients. The best time to feed your lawn is September.

If you want to test your soil, get a test kit at stores that sell fertilizer, University of Maine Cooperative Extension Offices, Soil & Water Conservation Districts, or call the state soil lab at 581-3591.
Together, we can have green lawns and clear waters!
This column was submitted by Barbara Welch, Lakes Education Coordinator with the Maine Department of Environmental Protection's (DEP) Bureau of Land and Water Quality. In Our Back Yard is a weekly column of the DEP. E-mail your environmental questions to infoDEP@maine.gov or send them to In Our Back Yard, Maine DEP, 17 State House Station, Augusta, ME 04333.