GRAINS-Futures tumble on concerns about economy and elections

* Falling equities, firm dollar spur risk-off day
* Renewed worries about euro zone economic crisis
* Upcoming big South American soy crop lends pressure
* Demand rationing keeps pressure on corn
* Wheat down but finding underpinning

(Updates prices, recasts, adds details of economic impact)
By Sam Nelson
CHICAGO, Oct 23 (Reuters) - U.S. grain futures tumbled on
Tuesday as the dollar rose and equities fell on renewed concerns
about the global economy, with soybeans dropping nearly 1
percent, the biggest one-day loss in a week.
Wheat slid more than 1 percent, reversing four consecutive
days of gains, and corn also eased on signs of continued tepid
export sales of U.S. corn due to historic high prices. Corn also
was under pressure from hints that U.S. cattle feeders were
scaling back operations because of continued poor profits due to
high feed costs.
"Risk-off is in control at the moment, as the weaker equity
markets are casting a long shadow on the markets this morning,"
said Sterling Smith, futures specialist for Citigroup.
At 10:18 a.m. CDT (1518 GMT), Chicago Board of Trade
November soybean futures were down 0.84 percent, or 13
cents, at $15.33-1/2 per bushel, December corn was down
1.44 percent, or 11 cents, at $7.50-1/4 per bushel, and December
wheat was down 1.88 percent, or 16-1/2 cents, at $8.61-3/4
per bushel.
"I would suggest that the outside markets' firming is a
return to risk-off trade in favor once again of buying the
safe-haven assets of the dollar and bonds," said Mike Zuzolo,
analyst for Global Commodity Analytics.
U.S. stocks slid more than 1 percent as poor earnings from
major multinationals heightened fears about the weak global
economy and as Moody's downgraded credit ratings for five
regions in Spain.
The Thomson Reuters Jefferies Commodity Research Bureau
index was down 1.43 percent at 299.1669.
At 10:20 a.m. CDT (1520 GMT), the dollar index was up
0.45 percent, New York crude oil was down nearly $2.50
per barrel, gold was down 0.83 percent, or $14.40 per ounce
, and the Dow Jones stock index was down 1.78 percent.
"It could be that some of this weakness in the outside
markets is a post-debate sell-off on fears of potentially seeing
increased trade tensions with China develop ... regardless of
who wins the U.S. presidential election," Zuzolo said.
In their third and final debate on Monday, President Barack
Obama and Republican challenger Mitt Romney vowed to get tough
on China's trade policies. The U.S. presidential election will
be held Nov. 6.

POTENTIAL BIG SOUTH AMERICAN CROP LENDS PRESSURE
Prospects for a bumper soybean harvest in South America
early in 2013 also contributed pressure to the soy complex,
although losses were slowed by current tight stocks of soy, firm
cash soybean markets, slow farmer selling, and waning harvest of
the 2012 U.S. soybean crop.
Brazilian analyst Safras e Mercado raised its estimate of
the country's soybean production to a record 82.5 million tonnes
from its July estimate of 82.3 million due to farmers' expanding
the area planted with the oilseed.
Corn found lingering pressure from the release on Friday of
a U.S. government cattle-on-feed report that showed the number
of cattle placed in America's feedlots in September was well
below analysts' average estimate and was the lowest September
figure on record. Fewer mouths to feed in upcoming months would
mean lower demand for corn, which remains priced at historically
high levels.
And on Tuesday, the U.S. Department of Agriculture (USDA)
said private exporters switched to non-U.S. corn for a
270,000-tonne sale to Mexico, further evidence of a marked
slowdown of exports of U.S. corn.

WHEAT LOWER BUT FINDS UNDERPINNING
Wheat prices were lower as the market fell back slightly
after rising for four consecutive sessions. But prices remained
underpinned by concerns about crops in Australia and the United
States and the prospect of an export ban in Ukraine.
Chicago wheat futures rallied nearly 2 percent last
week after setting a two-month low early in the week. The rally
was helped by diminishing prospects for the Australian crop and
expectations that Ukraine could ban exports from Nov. 15.

"The world balance sheet for wheat is tightening with major
exporters, but the United States is still missing out on export
business," said Brett Cooper, a senior markets manager at
FCStone Australia.
Traders said on Friday that Ukraine's agriculture ministry
would ban exports of wheat from Nov. 15 after bad weather hit
the harvest.
Commerzbank, in a market note, pointed to a Ukrainian ban as
a factor supporting European wheat.
"This improves in particular the export prospects for the
EU, which is already making European wheat more expensive - its
price has meanwhile overtaken that of U.S. wheat," Commerzbank
said.
November milling wheat in Paris was down 0.10
percent, or 0.25 euro, at 262.75 euros per tonne.
Prices at 10:23 a.m. CDT (1523 GMT)

LAST NET PCT YTD
CHG CHG CHG
CBOT corn 750.50 -10.75 -1.4% 16.1%
CBOT soy 1532.50 -14.00 -0.9% 27.9%
CBOT meal 467.10 -3.90 -0.8% 51.0%
CBOT soyoil 51.02 -0.64 -1.2% -2.1%
CBOT wheat 862.25 -16.00 -1.8% 32.1%
CBOT rice 1487.00 -3.00 -0.2% 1.8%
EU wheat 262.75 -0.25 -0.1% 29.8%

US crude 86.16 -2.49 -2.8% -12.8%
Dow Jones 13,102 -244 -1.8% 7.2%
Gold 1709.80 -18.49 -1.1% 9.3%
Euro/dollar 1.2962 -0.0097 -0.7% 0.1%
Dollar Index 79.9980 0.3460 0.4% -0.2%
Baltic Freight 1109 72 6.9% -36.2%

(Additional reporting by Nigel Hunt in London, Naveen Thukral
in Singapore and Michael Hogan in Hamburg; Editing by Marguerita
Choy)