GRAINS-Wheat, soybeans and corn fall ahead of USDA crop forecast

* USDA world/supply demand estimates at 1600 GMT

* USDA expected to show large world wheat supply

* Forecasts of U.S. corn, soybean yields in focus

(Recasts with European trade, adds new comment, changes dateline) HAMBURG, Sept 12 (Reuters) - Chicago wheat, soybean and corn futures fell on Tuesday, as investors awaited closely-watched world supply and demand reports from the U.S. Department of Agriculture (USDA). Chicago Board Of Trade December wheat fell 0.3 percent to $4.33-1/4 a bushel at 1016 GMT, having closed down 0.7 percent on Monday, after hitting a low of $4.31-1/2 a bushel, the weakest since Aug. 31. November soybeans fell 0.2 percent to $9.57-1/2 a bushel after dropping on Monday to $9.56-3/4 a bushel, the lowest since Sept. 5. December corn fell 0.5 percent to $3.55 a bushel. The USDA is due to publish its monthly World Agricultural Supply and Demand Estimates (WASDE) at 1600 GMT along with crop production reports. "Soybean, corn and wheat markets are drifting down today in positioning ahead of the USDA reports," said Matt Ammermann, commodity risk manager at INTL FCStone. "In corn and soybeans, a major focus is what yields the USDA will forecast for the U.S. crops after some poor weather this year." Analysts in a Reuters poll expect the USDA to trim its U.S. 2017 yield estimates for corn and soybeans. "The USDA regularly provides the market with surprises but overall the expectations are for a slight cut in U.S. yield forecasts for soybeans and corn," Ammermann said. "The U.S. crop conditions report did not provide big surprises late on Monday. So investors are taking a fairly relaxed view as we wait for the USDA numbers." The USDA said on Monday the condition of the U.S. corn crop was unchanged on the week while the condition of the soybean crop was only slightly down.

In Iowa, the top U.S. corn producer, USDA said 15 percent of the crop was mature, below the five-year average of 28 percent. The corn crop in the No. 2 producer, Illinois, was 26 percent mature, compared to the five-year average of 41 percent. Wheat fell despite major exporter Australia on Tuesday cutting its forecast for 2017/18 wheat production by nearly 10 percent to an eight-year low, as dry weather cut yields . "Wheat markets are weaker today as there are expectations the USDA will give a new reminder that world wheat supplies are looking ample, with big crops expected in the Black Sea region, especially Russia," said Charles Clack, Commodity Analyst at Rabobank. "This will mean more competition in global export markets for U.S. wheat." Grains prices at 1016 GMT

Contract Last Change Pct chg Two-day chg MA 30 RSI CBOT wheat 433.25 -1.50 -0.35% -1.03% 451.44 44 CBOT corn 355.25 -2.25 -0.63% -0.42% 364.97 54 CBOT soy 957.75 -2.25 -0.23% -0.44% 950.79 55 CBOT rice $12.67 $0.01 +0.12% +29.15% $10.11 47 WTI crude $47.92 -$0.15 -0.31% +0.93% $48.10 49


Euro/dlr $1.1957

Most active contracts Wheat, corn and soy US cents/bushel. Rice: USD per hundredweight RSI 14, exponential

(Reporting by Michael Hogan; additional reporting by Naveen Thukral; editing by Alexander Smith)