Most lawns in New York already have enough phosphorus and don't need supplementation, especially if clippings are left on lawns, according to recent research by Marty Petrovic, a turf specialist at Cornell. He says that new guidelines can help promote an eco-friendly lawn.
"The first step to minimize the environmental impact of your home lawn is to raise the mower's blade to a height of 3 to 4 inches -- usually the highest setting on your mower -- and leave the grass clippings on the lawn to recycle nutrients," says Petrovic.
Taller grass competes better with weeds and sinks roots deeper into the soil to better withstand midsummer heat and drought, explains Petrovic, and such lawns require less watering and prevent soil from washing away.
In analyzing soil tests sent to the Cornell Nutrient Analysis Laboratory for lawn fertilizer recommendations, Petrovic found that at least 80 percent had enough phosphorus already. When soils are extremely high in phosphorus, Petrovic has found that it dramatically increases the amount that runs off into lakes and streams, where it can promote algae blooms and eutrophication (excessive nutrients in the water) and reduce water quality.
Other tips to promote a "green," eco-friendly yard:
"A quarter- to half-inch application of a typical composted manure product may have 8,000 times more phosphorus than a year's worth of a commercial product's season-long weed and feed program," says Petrovic. "That's a century's worth of phosphorus in a single application."
To get the benefits of organic matter without too much phosphorus, consider yard waste composts, suggests Petrovic. They are generally lower in phosphorus than most manure-based products.
For more lawn care information, including the online publication "Lawn Care Without Pesticides," visit http://www.gardening.cornell.edu/lawn.
Craig Cramer is an extension support specialist in the Department of Horticulture.