Feed your lawn in the fall, and use an organic lawn fertilizer, such as compost or corn gluten.

Annoying, sure, but fall leaves fertilize your lawn better than anything in that comes in a bag.

RODALE NEWS, EMMAUS, PA—If you're looking for the best organic lawn fertilizer, look no further than the grass clippings and fall leaves dotting your backyard. Not only are they free, using them instead of commercial fertilizers that contain synthetic nitrogen and phosphorus could also save marine life in your community's ponds and rivers. A new study offers the first evidence that banning homeowners from using phosphorus-based lawn fertilizers helps bring depleted waterways back to life. The research was published in the most recent issue of Lake and Reservoir Management.

THE DETAILS: Various state and local governments across the country have banned lawn fertilizers containing phosphorus, due to the wildlife-depleting algae blooms those fertilizers feed in nearby waterways. However, the authors note, until now there hasn’t been hard evidence that those bans have any affect, and that may be why more states haven't adopted them.

These authors collected water samples from three areas of the Huron River near Ann Arbor, MI, which prohibited the use of phosphorus-based fertilizers in 2007, at weekly intervals from May to September 2008. They measured phosphorus levels from one location upstream from Ann Arbor, where the ban wouldn't have any affect, and then in two spots downstream, and compared those levels with similar readings that had been taken from 2003 to 2005. The average reduction in total phosphorus levels after the ban went into effect was 31 percent.

WHAT IT MEANS: Swap out your synthetic fertilizers for compost and other kinds of organic lawn fertilizer, and you can enjoy a healthy lawn as well as healthy rivers and streams. In fact, your turf probably doesn't need fertilizers juiced up with phosphorus, anyway. "I've read studies that show 90 percent of American lawns already have enough phosphorus," says Paul Tukey, founder of the Safe Lawns Foundation and author of The Organic Lawn Care Manual (Storey Publishing, 2007). The nutrient exists naturally in most soil, at levels high enough to provide your grass with the amounts it needs, he says.

You'll also cut down on the need for fertilizers if you just keep your lawn healthy, and fall is the perfect time to get started, Tukey says. "If you set your lawn up right in the fall, you don't have to fertilize in the spring."