NOTE: The US Department of Agriculture (USDA) is scheduled to release its US acreage and quarterly stocks reports on Friday at 11 a.m. CDT (1600 GMT).
Friday is also first notice day for deliveries against CBOT July futures contracts.
WHEAT - Down 1 to 2 cents per bushel
Wheat drifts lower on forecasts for improving harvest weather in the US Plains winter wheat belt and spillover pressure from corn and soybeans.
Traders also adjusting positions ahead of Friday's USDA acreage and quarterly stocks reports.
Statistics Canada said Canadian farmers reported seeding 24.6 million acres to wheat for 2019, down from 24.7 million in 2018.
Wheat production in Russia is expected to be 81.7 million tonnes this year, up 13pc from 2018, as hot, dry conditions have had a limited impact on yields, French consultancy Agritel said.
CBOT September soft red winter wheat last traded down 1-1/2 cents at $5.38-1/2 a bushel. K.C. September hard red winter wheat was last down 3-1/2 cents at $4.74-3/4 while MGEX September spring wheat was up 2 cents at $5.59.
CORN - Down 3 to 4 cents per bushel
Corn heads lower after a two-session advance, pressured by a slight improvement in US Midwest weather this week and position-squaring ahead of the USDA's acreage and quarterly stocks reports on Friday.
CBOT September corn last traded down 3-3/4 cents at $4.49-1/4 a bushel.
SOYBEANS - Down 3 to 4 cents per bushel
Soybeans lower on slightly improved US Midwest crop weather that may aid late planting in a few areas, and on position-squaring ahead of the USDA's acreage and quarterly stocks reports on Friday.
The USDA said private exporters sold 145,000 tonnes US soybeans to unknown destinations for delivery in the 2018/19 marketing year that began Sept. 1, 2018.
Statistics Canada said Canadian farmers reported seeding 21.0 million acres to canola in 2019, down from 22.8 million in 2018.
CBOT July soybeans last traded down 4 cents at $8.99-1/2 per bushel.