December wheat futures at CBOT added 0.6% to $4.31 1/2 per bushel.
January soybeans were down 2.75 cents at 9.8425 US dollars per bushel as of 1610 GMT in the morning trading, December corn was down 0.75 cent at 3.4275 dollars, while December wheat was down 7.25 cents at 4.2425 dollars.
CBOT January soybeans last traded down 3-1/4 cents at $9.83-3/4 per bushel. This pushed up in advance the soybean prices while dragging down the corn futures earlier this week.
The corn harvest was 82 percent completed, behind 90 percent for both last year's pace and the five-year average.
However, a record large short position in corn market might not be maintained too long and a South American weather problem would trigger some rallies, they added. The revised global stock forecasts of the ageny for 2017-18 are at 267.53 million metric tons - a record high.
In other news, CME Group will be inaugurating the trades of Black Sea wheat and corn futures based on S&P Global Platts' price rates soon which is targeted for the fast-growing exporting regions.
It is expected that USA wheat inventories will decline further into 2019, but the overall structure of the wheat market won't change without severe drought in the European Union or Black Sea region next year.
US soybean production is forecast at 4.425 billion bushels, down 5 million due to a fractionally lower yield. In response, the soybean futures took back nearly all of the early week gains and closed this trading week fractionally higher. The CBOT January soybean contract dipped to $9.82-1/2 a bushel ahead of the daily pause in trade, its lowest since October 31 and just below its 50-day moving average.