By Christine Stebbins

BIG ROCK, Illinois (Reuters) - Steve Ruh, a 42-year-old farmer harvesting some of his 3,000 acres of corn and soybeans 50 miles west of Chicago, says he could not be more pleased with how this year's harvest is going.

Ruh, sitting inside the high-tech cab of his $250,000 Case International combine, has one eye on the yield monitor and another on the eight rows of corn he is harvesting as he steams through another mile-long stretch of seven-foot high corn stalks one chilly morning this week.

"You can almost make marketing decisions as you're going through the fields," said Ruh who was checking a digital screen that recorded yields and moisture content of the corn as it moved from the field into the combine.

Ruh said his soybean yields were a "pleasant surprise" this fall, averaging about 10 bushels an acre above 2010 or about 60 bushels an acre. Corn yields so far are "pretty variable" but averaging 180 to 220 bushels an acre, or five to six bushels more than a year ago.

As the U.S. corn and soybean harvests pass the halfway mark, farmers like Ruh are finding wide variations in productivity.

Farmers often call corn yellow gold because of the export and ethanol demand which pushed prices to record highs this summer. Prices have backed off since but are still $1 higher than a year ago at about $6.50 per bushel.

Ethanol makers consume 40 percent of the U.S. corn crop -- the world's largest -- with Illinois and Iowa together producing one-third of the entire crop.

"One of the biggest deals about this year's crop is the variability -- much more so than it has been in probably 20 years," Ruh said.

CROPS FANTASTIC TO STRUGGLING

Heavy spring rains across the eastern Corn Belt delayed corn and soy planting, putting those crops off to a slow start. Once the rains shut off, America's breadbasket turned hot with July average temps among the highest on record.

"There are pockets where the corn is fantastic and soybeans are fantastic. There are pockets where it didn't rain from July 4th on and they're struggling," Ruh said.

The variability in the crop sparked the U.S. Department of Agriculture to cut its forecasts of both crops this season.

Paul Georgy, president of farm advisory Allendale located near Chicago, agreed on the variability of the 2011 US crop.

"In northern Illinois I think the corn yields are good and they probably weren't expecting as good as yields as we're seeing," Georgy told Reuters.

But that is not the case across the Midwest.

"This year's harvest is extremely variable. We've got producers in western Illinois, they've got the greatest bean crop ever. In Nebraska, some are reaching 80 to 85-bushel-an-acre soybeans. Then you can go 10 miles away and they could have 40-bushel-an-acre beans," Georgy said.

Another Illinois farmer harvesting corn 60 miles north of Big Rock, near the Wisconsin border, echoed the same sentiments.

"So far I'm pleasantly surprised at what I'm finding out in the field, considering the weather that we went through this summer with it being hot and dry. Then we had a couple of deluges of rain. But overall I think the crop is fairly decent," said Bruce Meier of Hebron, Illinois, who just started harvesting corn this week after finishing beans last week.

"There are places ... where it's going over 200 but the field average is probably going to be 185," said Meier, referring to a field that he was just harvesting.

The average 2010 corn yield in Illinois was 157 bushels per acre and soybeans were 51.5.

Both farmers are storing as much corn as they can on their farms to improve marketing returns. It also speeds up harvest as they avoid long lines at local elevators to dump grain.

Ruh, who has enough storage for 250,000 bushels of grain, said he generally sells his soybeans out of the field, hauling them to a nearby river terminal at Morris where ADM, Cargill and Elburn Co-op load barges and containers -- the latest export trend in shipping.

"I try to market at least 50 percent of my (corn) crop before harvest. We are filling the bins here today and we'll gamble with the other 50 percent," Ruh said.

(Reporting by Christine Stebbins; Editing by Bob Burgdorfer)