* Soybeans fall on technical trading before weekend

* Wheat turns down, after technical bounce early in session

* Lack of export demand continues to weigh on bean market

(Rewrites throughout with updated prices, wheat harvest detail, market analyst comment, US debt ceiling detail)

CHICAGO, May 19 (Reuters) - Chicago Board of Trade (CBOT) soybean futures slid sharply on technical trading on Friday, as investors rushed to liquidate their positions ahead of the weekend, traders said.

The most-active soybean contract fell to the lowest prices seen since July - and several new-crop soybean contracts also plunged to new contract lows - amid poor U.S. export demand, and a new forecast estimating that Brazil's soybean crop would be bigger than expected.

And commodity and financial markets roiled late in the day, after U.S. House Republicans and President Joe Biden's Democratic administration on Friday paused talks on raising the federal government's $31.4 trillion debt ceiling, as the deadline to avoid default ticked closer.

"It's a fragile market and the end of a poor technical trading week," said Don Roose, president of Iowa-based U.S. Commodities. "The market is looking to see if we can set a new floor."

Corn and wheat futures spent the day in choppy trading, as a spate of bargain buying early in the trading session pulled prices up in a technical rebound from sharp lows a day earlier.

Poor harvest prospects in the U.S. Plains initially gave wheat futures a boost: Wheat yield potential in Kansas was estimated on Thursday at its lowest since at least 2000 in an annual field tour.

But corn and wheat futures also ended the day on a down note, with July hard red winter wheat at one point touching down to the lowest price seen since May 5.

"We've seen some of the weak short positions get flushed out of the market, but no one is stepping in to buy on the rallies," said Karl Setzer, brokerage research lead with Mid-Co Commodities.

CBOT's most-active soybeans settled 26 cents lower at $13.07-1/4 per bushel. The most-active corn settled down 3/4-cent at $5.54-1/2 a bushel, while CBOT wheat settled down 6-3/4 cents to $6.05 a bushel. (Additional reporting by Gus Trompiz in Paris and Naveen Thukral in Singapore; Editing by Grant McCool)