NEW YORK (Reuters) - About six years ago, an army of agents hired by energy companies started desperately courting landowners across the United States whose farms and ranches happened to sit atop some of the richest oil and gas deposits in the world. And so began one of the biggest land grabs in recent memory.

Those days are over.

U.S. energy titan Chesapeake Energy is quickly cutting back on an aggressive land-leasing program that in recent years has made it one of America's largest leaseholders, putting an end to half a decade of frenzied energy wildcatting.

Beset by growing governance and financial problems, and a sharp slump in natural gas prices, the No. 2 U.S. gas driller is reducing by half the ranks of its agents, known in the industry as landmen.

With little evidence that its competitors are taking on the role of leading industry lease-buyer, Chesapeake's new found frugality is expected to usher in a more sedate period of U.S. land buying, and a sizeable cultural shift for an industry that has been acquiring new acreage at almost any cost.

A surge in drilling into rich shale-gas seams from Pennsylvania to Texas has pushed natural gas prices to 10-year lows, forcing producers, including Chesapeake, to cut output and put the brakes on new wells.

Drilling simply to hold on to leases represents about half of U.S. natural gas output, analysts say, which has helped keep production at record highs despite plummeting prices. Leases held by energy companies tend to last about three years, but will typically remain valid indefinitely if an energy company drills wells and produces fuel on the leased acreage.

It should be fairly easy for drillers to re-hire agents and secure more land when prices recover, according to landmen sources, and production is not expected to be affected immediately. But a lull in leasing could briefly affect production longer term, given that it takes up to six months to secure large tracts of land.

"Chesapeake has always been a bellwether for where the next big play is. It would come, lease large blocks and send a signal to the market," said Adam Bedard, senior director at Bentek Energy in Colorado. "Without them, the pace of land acquisition might slow."

In a move to mollify disgruntled shareholders, Chesapeake plans to reduce its use of contracted landmen from 1,300 now to 650 by the end of the year, said Chief Executive Aubrey McClendon, who was stripped of his chairmanship last month after Reuters reported a series of governance missteps.

The reduction, which is expected to help reduce towering debt levels, marks an 80 percent decrease from its peak of 3,400 landmen, McClendon said.

CULL BEGINS

The cull has begun. Over the past month, 225 contracted landmen were cut from Chesapeake jobs, said one Ohio-based landman, who, like most in the close-knit industry, would only speak off the record.

"Chesapeake's activity level in the Appalachian region is minimal now. It has devastated the (landman) industry," the source said. "The Chesapeake debacle is one thing, but the rest of the industry shortfall is because a lot of the projects are intertwined with Chesapeake," he added.

The Oklahoma-based company has become one of the largest leaseholders in the United States, amassing more than 15 million acres of land for drilling or an area about the size of West Virginia.

One mid-sized U.S. brokerage that does lease work for Chesapeake has experienced a 15 percent to 20 percent fall in business over the last 90 days due to a slowdown not just in Chesapeake activity but across the board, a manager for operations at its eastern division told Reuters. About 15 percent of that company's business comes from Chesapeake, he said.

"We are getting to the point where companies are becoming more cautious - that is what we are seeing," he said, asking that he not be named.

Other major producers, including Encana Corp, Royal Dutch Shell and Chevron, said they are not planning to materially change their strategy of land acquisition or staffing numbers, suggesting a gap might be left as Chesapeake, long the pioneer in drill leasing, retreats.

"We have not reduced our land staff nor have we made any changes in the way we conduct land operations," said a spokesman for Encana, one of Chesapeake's main land-leasing rivals. Encana employs an in-house staff of about 170 workers in its land department. Shell also said it was "not planning any major staffing level changes in our land function for leasing activity."

THE GLUT

Landmen in the field reckon companies are now well-placed to increase leasing again when they need to, but it could take up to six months between a decision to lease the land and the drilling, potentially creating a lull in activity, sources said.

While a fall in leasing will affect the landmen, it is unlikely to affect gas output for quite some time given the amount of land already leased and the hundreds of wells drilled that have yet to begin producing.

"The huge land grabs in the gas plays are coming to an end," said one energy hedge fund manager. "Even without more leasing, however, these companies have backlogged a huge inventory of drilling locations."

The backlog of 3,500 oil and gas wells in the United States is about 1,000 more than usual, according to Randall Collum, a natural gas analyst at Genscape in Houston.

It could take more than a year to exhaust the natural gas portion of that supply as pipelines come online to connect new producing regions, such as in Ohio, to areas of higher demand, he said. Moreover, the reserves accumulated over the last decade are expected to take longer to dwindle away.

That scenario is likely to put a cap on prices in the near term, with or without Chesapeake.

AFTER THE BOOM

When U.S. drillers employed new technologies during the last decade to economically tap oil and gas from shale rock, results showed the potential for a massive revival in waning domestic production.

In 2006 and 2007, companies began rushing to acquire new leases. Geologists pored over maps, in search of the sweetest acreage. Landmen were hired like never before, court houses in energy-rich regions filled with workers quickly securing leases. Rural and depressed areas in Pennsylvania, North Dakota, and Ohio became, by geological coincidence, new target areas for energy companies.