The heavy equipment has been hauled out as part of the campaign to restore one of the Bay’s most delicate resources.

A custom-designed boat, akin to an aquatic tractor, was used in October to plant two acres of underwater grasses in Virginia rivers — one of the largest grass bed plantings ever in the Bay.

Planting submerged aquatic vegetation is normally a painstakingly slow job, with plants carefully handled by scuba divers who place them, one at a time, into the sediment.

But in a few hours, the aquatic tractor planted an acre of eelgrass — 20,000 plants in all — in the Rappahannock River. The next day, it planted another acre in the James. The same job would have taken teams of trained divers several times as long to complete.

“If I didn’t see the plants go in, I wouldn’t have believed it,” said Jill Bieri, an underwater grass specialist with the Chesapeake Bay Foundation, which arranged to have the planting device brought from Florida for a test.

The aquatic tractor is actually a pontoon boat fitted with a pair of 9-foot metal wheels that roll along the river bottom. A worker places a plant sprig in clips located about every three feet along the edge of the wheel. As the wheel rolls along, the plant is injected into the river bottom with a jet of air.

The boat has a wheel located along each pontoon, allowing two rows to be planted at the same time, dramatically accelerating the job. “It was a big leap for us to go from having a few kids out planting grasses to employing a farmer to plant two acres in these two rivers,” Bieri said.

With Bay grasses at only a fraction of their historic levels, there has been growing interest in jump-starting their return by planting unvegetated areas in the hope that the grasses will take root and spread.

But restoration efforts are labor intensive, and usually restricted to small patches which may be vulnerable to grazing sea turtles, burrowing cownose rays or other aquatic dwellers.

So Bieri began searching for methods that could plant more grasses faster. That led her to Florida farmer Jim Anderson, who designed the unique pontoon-tractor.

His invention was spurred as Florida officials began to restrict fishing in the state’s vanishing grass beds to keep boat propellers from ripping up the plants.

Anderson thought the best solution was to plant more grasses. So he took an old pontoon boat from his barn, combined it with other equipment, and developed the J.E.B. — Jim’s Environmental Boat.

In recent years, he’s planted several test sites off the Florida Keys, along the Texas coast and in other areas. Ultimately, he hopes to impress enough people to begin commercial production of the boats.

He quickly impressed observers in Virginia. State Del. Flora Crittenden, who accompanied the planting trip on the James, said she would try to persuade the state to buy a boat of its own. “I think she would have written a check if she had a checkbook there,” Bieri said. “She was real excited about it.”

The CBF, which spent $10,000 to bring the boat to the Bay for the experiment, is also considering whether to make such a purchase, Bieri said.

In a test of man vs. machine, the J.E.B. clearly appeared speedier. Bob Orth, a seagrass expert at the Virginia Institute of Marine Science and his colleague, Jamie Fishman — both experienced underwater grass planters — raced the craft to plant a 60-meter line of SAV. It took the J.E.B. four and a half minutes; the two humans took about three times as long.

Further, the machine has more stamina, Orth acknowledged. “There are only so many hours that a diver can work,” Orth said. “That machine can plant all the time.”

Still, the verdict is not in, Orth said. The scientists and the tractor planted side-by-side test plots at both restoration sites. Over the next year, they will be monitored to see if the plants placed by the J.E.B. fare as well as those placed by hand.

“That should tell us an awful lot about whether this machine is going to be OK,” Orth said. “It all depends on the success rate.”

Even it those tests prove successful, the J.E.B. will not be able to plant the hundreds of thousands of lost grass beds in the Chesapeake like so many fields of corn, Bieri acknowledged.

Many areas of the Bay and its tributaries lack the water quality needed to support grasses: They are clouded by sediment washed off the land, or filled with algae because of too many nutrients in the water. That blocks the sunlight which the grasses, like all plants, need to survive.

“The most important thing is water quality,” Bieri said. “The only way these large areas that we plant are going to survive is if we have good water quality.”

Also needed, she said, is a supply of grasses to plant. In upper parts of the Bay, where freshwater and low-salinity grasses thrive, that is less of a concern. Those species can be reared in classrooms, laboratories and other places before being transplanted into rivers.

But high-salinity parts of the Bay, where eelgrass dominates, are more problematic. Eelgrass has not been successfully reared in laboratories, so the main source of plants is extracting them from healthy beds.

“The limiting factor is plant supply,” Bieri said. “Obviously we can’t go in and do these transplants more than a couple times a year if we are taking from natural beds. It kind of defeats the purpose.”

For the James and Rappahannock plantings, teams of volunteers worked to pull plants out of healthy beds, which required a state permit. Although the area disturbed was probably only about 10 square meters, Bieri said it was a practice she would like to get away from.

In all, she estimated that about eight to 10 acres of underwater grasses might be planted a year with one of Anderson’s aquatic tractors. About 2 acres might be eelgrass, she said, with the rest being freshwater species.

Although the J.E.B. — if it proves successful — could put large-scale projects into high gear, Bieri said it would not eliminate the need for volunteers. Getting hands-on involvement, whether by rearing grasses or helping to place them in rivers, is important because it helps to build appreciation for the resource. “Education is part of restoration,” she said.