GRAINS-Wheat up 1 pct, soy turns lower on end-of-year positioning

(Updates U.S. market activity to close, adds analyst comments; changes byline, dateline, previously SINGAPORE/PARIS)

CHICAGO, Dec 27 (Reuters) - U.S. wheat futures climbed more than 1 percent on Wednesday while corn was higher for the sixth straight session as technical buying and end-of-year positioning buoyed grain prices, traders and analysts said.

Soybean futures turned lower on the Chicago Board of Trade after an earlier 1-1/2-week high on profit-taking and alleviated dry weather concerns in Argentina, where weekend rainfall benefited emerging soy plants.

Bitterly cold temperatures in the U.S. Plains threatened to damage dormant winter wheat plants, further supporting wheat prices. Trading volumes remained light ahead of Monday's New Year's Day holiday, leaving prices vulnerable to increased volatility due to a relative lack of liquidity.

CBOT March wheat settled up 5-3/4 cents at $4.28 per bushel and CBOT March corn up 1 cent to $3.53-3/4, a roughly two-week high.

"It's too early to determine any kind of threat (of winterkill)," said Frontier Futures wheat broker Joe Nussmeier. "More than anything, it feels like managed money is trying to cover (their short positions)."

Investment funds were holding a near record-large net short position in U.S. wheat futures and had sizable net shorts in corn and soybeans, according to regulatory data released last week.

Funds on Wednesday were net buyers of wheat and corn, and sellers of soybean futures contracts, traders said.

CBOT January soybean futures ended down 3-3/4 cents at $9.55-1/2 per bushel.

"We're making bets on South American weather," said Zaner Ag Hedge chief market strategist Ted Seifried. "They've had some better rains in Argentina. The short-term forecast is kind of dry but there's optimism rains will come in the second week and fix the problem."

An explosion at a port operated by Chinese export company COFCO in Argentina's Rosario grains hub killed one person and injured others, local authorities said. It was unclear how the incident would impact operations at the port.

(Additional reporting by Naveen Thukral in Singapore and Sybille de La Hamaide in Paris; Editing by Meredith Mazzilli)