GRAINS-Corn hits contract low ahead of big U.S. harvest, wheat gains

(Updates U.S. market activity to close, adds comments) CHICAGO, Aug 29 (Reuters) - Chicago Board of Trade corn

futures fell to contract lows for the fifth straight

session on Tuesday on technical selling linked to the approaching harvest of a bumper U.S. crop, traders and analysts said.

CBOT wheat futures also notched life-of-contract lows

before reversing slightly higher on bargain buying while soy

prices were narrowly lower for the second straight day.

Global grain and soy supplies were ample and the trend remained downward even as some importers took advantage of the low prices, the dealers said. Exporters sold 226,000 tonnes of U.S. corn to Mexico and 198,000 tonnes of U.S. soybeans to China, according to the U.S. Department of Agriculture, while Egypt bought 295,000 tonnes of wheat from Russia and Ukraine in a tender in which no U.S. supplies were offered.

CBOT December corn settled down 2-1/4 cents at $3.48-3/4 per bushel. CBOT December wheat firmed 1-3/4

cents to $4.29-3/4 after hitting a lifetime low of $4.22-1/2.

Corn and wheat on continuous charts each fell to

the lowest since December "Corn charts made a new contract low with all momentum down," ED&F Man Capital analyst Charlie Sernatinger said in a client note, adding that U.S. farmers continued to sell supplies out of storage ahead of the harvest of a new crop.

CBOT November soybean futures eased 4 cents to

$9.37-1/4 per bushel, edging lower after the USDA late on Monday unexpectedly boosted condition ratings for the U.S. soy crop. USDA on Monday said 61 percent of the soybean crop was in good to excellent condition, up from 60 percent last week. Analysts surveyed by Reuters expected soy ratings to stay steady. USDA said 62 percent of the U.S. corn crop was in good to excellent condition, unchanged from last week. Investors were beginning to square their positions ahead of the three-day U.S. Labor Day holiday weekend, and short-covering ahead of the weekend could provide support to prices, said Price Futures Group broker Jack Scoville. "We're just consolidating," Scoville said. "No one wants to take a short home because some weather might develop." Tropical Storm Harvey rainfall halted port loadings at wheat terminals in Texas, and the storm could delay corn and soy harvest in the Mississippi River Delta region later this week. There was a small chance frost could develop in the northern Plains, which could damage corn plants there, agriculture meteorologists said.

(Additional reporting by Michael Hogan in Hamburg and Colin Packham in Sydney; Editing by Susan Thomas and Meredith Mazzilli)