Bills that would restrict the nutrient content of fertilizer applied to lawns will be considered in Maryland, Virginia and Pennsylvania legislatures this year as part of strategies aimed at reigning in all sources of nutrient pollution.

The measures are being championed by members of the Chesapeake Bay Commission. They would restrict the display of fertilizer containing phosphorous, which could only be sold for newly established lawns, or lawns where soil tests showed phosphorus was needed. Nitrogen concentrations in fertilizers would also be limited and no de-icing agents containing fertilizer could be sold.

The exact elements of the bills vary slightly state-by-state, but they generally would restrict the use of fertilizer during the winter, or when the ground is frozen, or the spreading of fertilizer near water bodies. Commercial applicators would need to be licensed and trained and keep records of the amount of nutrients they applied to the land and plants.

The legislative push followed presentations on lawn fertilizer at the January meeting of the commission, an advisory panel that represents the legislatures of the three states. The measures would help with watershed implementation plans in all three states, which called for new actions to control runoff from lawns to help meet overall nutrient reduction goals.

A recent study found that grass covers about 3.8 million acres, or 9.5 percent of the Bay watershed.

Nonetheless, it's unclear that it's a significant contributor of nutrient pollution to the Bay, as grass is a perennial crop that readily absorbs nitrogen. Further, studies show about half of the population doesn't fertilize their lawns, and most of those who do apply less than is recommended.

Nonetheless, nutrients can still run off if overapplied, applied before storms or carelessly spread onto paved surfaces.

"We are going to see a reduction in nitrogen that causes a problem from the legislation," said Gary Felton, an associate professor at the University of Maryland who has worked on urban nutrient management issues. "If we are looking for a silver bullet, we are looking in the wrong place. But will we see something that reduces? I think we will."

Felton said lawns and golf courses often are not the villains many imagine. He noted that in Queen Anne's County, groundwater nitrate levels dropped sharply after a cornfield was converted into a golf course. "That suggests to me that maybe the golf courses are not the great sin that some people would have you believe."

The removal of phosphorus may have more of an impact. At its January meeting, commission members heard from John Lehman, a scientist from the University of Michigan, who found that phosphorus levels in Michigan's Huron River dropped an average of 28 percent after Ann Arbor adopted an ordinance in 2006 that curtailed the use of phosphorus on lawns.

Felton noted, though, that companies have been phasing phosphorus out of their fertilizer, although that's not the case everywhere. Scotts, the largest fertilizer company, has reduced phosphorus levels 80 percent in residential fertilizer in the Bay states since 2006. Nitrogen concentrations have also been lowered.

"I feel like it is something that we really need to do because the farmers always point at the urban arena and say, 'You are not doing your part,'" he said. "Well the fertilizer companies kind of quietly did an awful lot. A lot of things have changed, but they haven't bragged about them, so nobody knows about them."