Down a dusty dirt road past a field of soybeans, Gov. Robert L. Ehrlich Jr. (R) came to Charles County on Friday to discuss crops and the water they can't live without.

Ehrlich warned state legislators, county commissioners and other local officials against "inappropriate development in the outer suburbs" and talked about how farmers, by planting crops that soak up nitrogen and phosphorous, can play an important role in cleaning up the Chesapeake Bay. Farmers "live with the importance of water," Ehrlich said.

The event on the Hancock family farm just south of La Plata was an opportunity to discuss two issues: the state's cover crop program and a study to determine the future water supply of Maryland's coastal plain counties.

The cover crop program, administered by the Maryland Department of Agriculture, pays farmers up to $50 an acre to plant crops such as rye or wheat in the fall and winter to absorb excess nutrients that might otherwise pollute the bay through runoff.

Across the state, 125,000 acres of farmland have been approved for the cover crop program. The crops are estimated to remove 1 million pounds of nitrogen and 25,000 pounds of phosphorous annually, agriculture officials said.

The state lacks funding for an additional 50,000 acres that have been requested by farmers, but Ehrlich said he is committed to fully funding the program.

In Southern Maryland, demand for the cover crop program has risen sharply: This year, farmers in St. Mary's County signed up for 3,982 acres, an increase of 131 percent over last year. Charles County had 3,351 acres, up 68 percent, and Calvert had 1,157 acres, up 40 percent.

"It's a good incentive; it does a good job," said David Hancock, 47, a third-generation farmer who works about 1,500 acres in Charles County with his family. "It helps to hold the soil in place and also takes up that excessive fertilizer."

The other topic Friday was an announcement of a hydrologic study that will use computer modeling to outline the water supply in Southern Maryland and the Eastern Shore. The study comes after a state advisory committee in 2004 reported "an alarming realization that unless and until adequate measures are taken, Maryland will have great difficulties in the future meeting its growing water demand."

The report said Southern Maryland's population is projected to grow by 55 percent by 2030. Freshwater use in Southern Maryland, almost entirely dependent on aquifers, is expected to increase faster than in other parts of the state: from 32 million gallons per day to 45 million gallons per day in 2030, up 40.6 percent. In some areas, the demand has sent groundwater levels falling at a rate of two feet per year, said Kendl P. Philbrick, secretary of the Maryland Department of the Environment.

Declining water levels "have the potential to impact future growth" and economic development, he said.

The data collected on seven major aquifers will allow hydrogeologists and water regulators to assess supply, water quality and areas of potential saltwater intrusion, said David Bolton, chief of hydrogeology at the Maryland Geological Survey. Over the next two years, the Department of the Environment will spend $200,000 to $300,000 to start the project, officials said.

"It's not a project that has an end," said Robert M. Summers, director of the state's water management administration. "It will be a living management tool."

Summers said that although Southern Maryland's water supply is now "abundant," it is "not unlimited" and "we need to be working on this now."

A preliminary report relating to the project, prepared by the Maryland Geological Survey last month, indicated that current rates of withdrawing water, particularly from the Waldorf area, are not sustainable over the next 25 years. It said future drawdowns of the aquifers could allow brackish water from the Potomac River to seep into freshwater supplies in the Indian Head area of Charles County and partially drain some wetlands.

Gov. Robert L. Ehrlich Jr. (R) and Pope Creek farmer Chandler Johnson. Ehrlich warned against "inappropriate development in the outer suburbs."