Soy down on demand worries, corn mixed as traders question lofty yield projections
- Soybeans down on export demand worries
- Corn mixed as disease, dry conditions threaten yields
- Wheat down as large Russian, Australian crops set to swell global supplies
U.S. soybean futures fell to a 1-1/2 week low on Tuesday as China continued to shun purchases from the United States and as forecasts for improved rains in the coming days reinforced expectations for a sizeable Midwest harvest.
Corn futures were mixed as traders returned from the long U.S. Labor Day holiday weekend. Losses were limited by concerns that pockets of yield-sapping disease and dry conditions in parts of the Midwest farm belt would trim yields as farmers prepare to harvest a record-large crop this autumn.
Wheat futures dropped, pressured by ample supplies from Northern Hemisphere harvests and a rebound in the U.S. dollar index 
DXY from a five-week low.
Grain traders have been weighing the U.S. Department of Agriculture's latest forecasts for record-large U.S. corn and soybean yields against scattered reports of disease pressure and drought-hit fields, while also monitoring forecasts for rain this week that could aid late-developing crops.
Strong export demand has kept a floor under the corn market, but a lack of new-crop soybean purchases by China and slow progress in securing a U.S.-China trade deal have kept soy futures under pressure.
"I think we have this decided shift pre-holiday versus post-holiday today. Friday, we had a corn-led rally and today we have a soy-led decline," said Mike Zuzolo, president of Global Commodity Analytics, citing "the lack of positive news or progressive news in the U.S. and China trade negotiations" that concluded over the weekend.
Beijing's hosting this week of non-Western leaders, including Russian President Vladimir Putin and Indian Prime Minister Narendra Modi, has underscored its geopolitical opposition to the United States.
Chicago Board of Trade November soybeans (SX25) were 15-3/4 cents lower at $10.38-3/4 a bushel by 12 p.m. CDT (1700 GMT), while December corn (CZ25) was down a penny at $4.19-1/4 a bushel.
CBOT December wheat (WZ25) fell 9-1/4 cents to $5.25 a bushel, on abundant supplies from exporters including Australia and Russia.
