The largest "crop" in the Bay watershed is no longer corn or soybeans, according to new research, but turf grass. More than 3.8 million acres of grass - or 9.5 percent of the 64,000-square-mile watershed - is made up of lawns or other grass-covered areas such as parks and golf courses, according to a soon-to-be-released paper.

That's slightly more than the amount of land covered by corn, soybeans, wheat and other row crops in the watershed, according to Tom Schueler, coordinator of the nonprofit Chesapeake Stormwater Network, and Peter Claggett, a research geographer with the U.S. Geological Survey, who independently analyzed different sets of data but came up with similar figures.

Overall, the amount of turf grass in the watershed appears to have tripled in the last three decades, according to ChesNet Storm News, the stormwater network's newsletter.

The turf grass champ, according to the researchers, is Maryland's Montgomery County, which has 140,272 acres, or 44.2 percent of the county, planted with grass.

But the county with the highest percentage is Virginia's Fairfax County, where 46.5 percent of the land, or 116,932 acres, is growing grass.

Even agricultural regions sprout a lot of grass. Pennsylvania's Lancaster County has 110,564 acres of turf, or 19.1 percent of its acreage.

Extrapolating from that data, Schueler estimates that 215 million pounds of nitrogen is applied to grass each year. Grass is highly effective at absorbing nutrients, but can produce runoff when fertilizer is used improperly.

And, surveys indicate that while watershed residents spend about $5 billion a year maintaining lawns, fewer than 10 percent of homeowners consult technical information on lawn management before applying fertilizer, according to Schueler.

Lawns in the watershed receive about 19 million pounds of pesticides per year, which are commonly found in urban streams.

Lawns also use a huge amount of water. During summer months, the equivalent of 7,875 cubic feet per second of water is applied to lawns. That's roughly equivalent to the freshwater flow of the Potomac River in the District of Columbia during the summer.

Lawn and garden equipment, which generally have poor pollution controls, are the second leading emitter of smog-causing pollutants in Maryland during the summer, just a bit behind cars and trucks.

There is an upside to lawns - they do provide a huge amount of space that could be used to hold stormwater runoff instead of diverting it down storm drains and into streams, according to Schueler.

"When you have an average of three acres of grass for each acre of impervious cover, there is an enormous opportunity to use grass as a stormwater sponge or filter," he wrote in the newsletter.

For information, visit www.chesapeakestormwater.net.