(Updates with closing prices, details from wheat tour)
By Mark Weinraub
CHICAGO, May 3 (Reuters) - Chicago Board of Trade corn, soybean and wheat futures fell on Tuesday, pressured by a round of profit taking and technical sales, traders said.
Soybeans set back from a 15-month high hit during the overnight session while corn and wheat faced resistance after failing to take out last week's peaks, sparking a sell-off led by investment funds.
"The funds giveth and the funds taketh away," said Bill Gentry, a broker at Risk Management Commodities in Lafayette, Indiana. "We have had several up days. This is a technical correction."
Wheat and corn futures, which faced additional pressure from a bearish fundamental picture amid improving U.S crop conditions and a fast pace of planting, notched the biggest declines.
CBOT July corn futures dropped 12 cents at $3.79-3/4 a bushel and CBOT July soft red winter wheat was 17 cents lower at $4.70-3/4 a bushel.
CBOT July soybeans were 13-3/4 cents weaker at $10.30 a bushel.
"There is just nothing bullish on corn and wheat," said Dan Cekander of DC Analysis. Corn is just off to a good start, and the wheat ratings keep getting better. You have gotten to a point where it is even hard to hold (up) the beans."
CBOT soft red winter wheat hit its lowest since April 18 and corn its lowest since April 25.
The U.S. Agriculture Department on Monday said good-to-excellent ratings for the winter wheat crop rose 2 percentage points to 61 percent in the week ended May 1.
Early results from the Wheat Quality Council's annual tour of Kansas showed that yield prospects for the hard red winter wheat crop in northern parts of the state were better than average.
USDA also said corn planting advanced 15 percentage points to 45 percent complete, well ahead of the five-year average of 30 percent.
Declines in soybeans were kept in check by concerns about production in South America, which could boost export demand for U.S. supplies.
Closely watched crop forecaster Informa Economics on Tuesday lowered its outlook for the Argentine bean crop to 55.0 million tonnes from 59.5 million. It also trimmed its Brazil soybean production view to 100.1 million tonnes from 100.5 million.
Argentina lost an estimated 9 million tonnes of soybeans in April storms that swamped the Pampas farm belt, an analyst with the state weather agency said on Monday. (Additonal reporting by Julie Ingwersen in Chicago, Naveen Thukral in Singapore and Gus Trompiz in Paris; Editing by David Evans, James Dalgleish and Marguerita Choy)