Maryland requires cities and farms to keep a close eye on nutrient runoff in the Chesapeake Bay, but a study released Monday says the state doesn’t pay enough attention to another major source of bay pollution: you and your thick, green lawn.

Grassy turf, not farmland, is the most dominant crop in the bay watershed. There were almost 1.3 million acres of planted turf in Maryland in 2009, compared with 1.5 million acres of all other crops, says the study by the Environment Maryland Research and Policy Center.

“Yet it is the least regulated of the state’s major crops,” the study says. That, the study says, has to change.

The study calls on Maryland to consider following other states, such as New York and New Jersey, which recently banned the use of fertilizers with phosphorous and imposed buffer zones around bodies of water.

“All 17 million of us who live in the watershed need to be part of the restoration effort,” said Sen. Benjamin L. Cardin (D-Md.). Not just wastewater facilities, municipalities and farmers, he said, but “homeowners and businesses also need to be part of the solution by reducing the chemicals we put on our lawns and other green spaces.”

Pollution in the bay increases when nutrients wash into its waters from snow and rainfall. And many lawn fertilizers have an excess of two problematic nutrients, nitrogen and phosphorous.

The study criticizes Maryland’s regulation of the state’s turf crop as lax. Tracking “fertilizer use on developed land is such a low priority that the state doesn’t keep statistics on it, but Maryland Department of Agriculture records show non-farm-use fertilizers are quickly catching up to farm fertilizer sales,” the study says.

The MDA didn’t respond to a request for comment. But Vernon W. Cooper, president of the Maryland Turfgrass Council, disagreed with the study, saying that turf is “one of the best filters to prevent damage to the bay,” because it acts as a sponge that filters nutrients from rain runoff.

“A weak or thin lawn allows more sediment to be washed in the bay,” Cooper said.

The state agriculture department pledged last year to make nutrient management a high priority but collected only one fine, according to the study,

On its Web site, the Maryland Department of the Environment addressed lawn care in reports and a pollution checklist for homes, offices and cars.

“Try to purchase ‘low phosphorous’ or ‘no phosphorous’ fertilizers,” it says. “Any fertilizer that falls on your sidewalks or driveway should be swept back into the grass.”

As a result of nutrient pollution, “more than 80 percent of the bay and its . . . tributaries are either low-oxygen or no oxygen,” said the study, “Urban Fertilizers and the Chesapeake Bay.” Furthermore, the bay and its waters are “plagued with . . . harmful algae blooms,” causing seafood harvests that support commercial fisherman to plummet.

In a watershed in suburban Baltimore, researchers found that 56 percent of nutrients in one stream came from lawn fertilizer.

The Environmental Protection Agency initiated an effort this year to reduce the bay’s “pollution diet,” which addresses turf runoff. The plan has been criticized by conservatives in Congress, municipalities in Virginia, home builders and farm groups.