A lack of significant rain so far this fall has U.S. farmers and government agriculture officials worried that the worst drought in 56 years, which devastated this year's U.S. corn and soybean production, will continue and hurt next year's crops.

The summer-long stretch of hot and dry weather in the Farm Belt slashed U.S. corn and soybean harvests this year. Two-thirds of the contiguous United States, including prime farm land in the Plains and Midwest, remain under moderate to severe drought as growers begin to plan for the new crop year.

"Even if it rains tomorrow, the consequences of this drought will be felt for years to come," said Agriculture Secretary Tom Vilsack at an Omaha workshop called to discuss federal aid for crop and livestock producers.

Doug Kluck, regional climate services director at the National Oceanic and Atmospheric Administration (NOAA), said dry spells can run for several years although it is impossible to forecast if there will be drought in 2013.

"Without a soaking rain, things are not going to get better quick," said Kluck. "I don't mean to be a black cloud but from a responsible point of view, you need to be prepared for the worst."

Drought will persist in the central U.S. Plains this fall while improvement is expected east of the Mississippi River and in the northern Plains, NOAA forecast recently. Dry weather in the Plains would threaten the upcoming winter wheat crop, it said.

Three-fourths of Nebraska, a major corn, wheat and livestock state, was under exceptional drought, the most severe category, said director Greg Ibach of the Nebraska Agriculture Department.

"The good news for dry land farmers is they will be able to rely on federal crop insurance," said Ibach.

Roger Elmore, an Iowa State University agronomy professor, said soils in the No 1 corn-growing state were so dry that fall tillage raised dust clouds. He said dry weather was expected to continue in the near term.

"If we don't get back to normal precipitation this fall, it may be hard to catch up in the spring. We don't want another dry year," Elmore told the Reuters Global Ag Forum on Oct 3.

To alleviate drought in Minnesota, six to 12 inches of rain are needed in most counties -- an improbably large amount to expect this fall, wrote Mark Seeley, a University of Minnesota climatologist last week. It would be more realistic, he said, to expect a modest recharging of soil moisture.

"A wet spring will be needed for a decent 2013 crop in Minnesota," said Seeley.

With the fall harvest speeding toward an early conclusion, USDA has forecast the smallest corn and soybean crops since 2004 due to drought and tight supplies for the year to come. USDA will update its estimates on Thursday.

Winter wheat sowing is running at normal rates, with 57 percent planted as of Monday, but emergence is far behind normal in Nebraska, Colorado and Montana, said USDA in a weekly report. (Reporting by Micheal Avok, Writing by Charles Abbott; Editing by Bob Burgdorfer)