CHICAGO: Chicago Board of Trade (CBOT) corn futures turned lower on Wednesday, traders said, as the market began to unwind the corn-wheat spread.

* CBOT September corn settled down 1-1/2 cents at $4.24 per bushel. New-crop December corn closed down 3/4-cent at $4.30-3/4 a bushel.

* Corn contracts rallied earlier in the day on short covering, as the market weighed whether further hot weather in the US Midwest could affect crop yields this fall, traders said.

* Very hot and dry weather could return to the US Midwest in the next two weeks, particularly in parts of top-corn producing states Illinois, Iowa and Indiana, according to a report by Commodity Weather Group on Wednesday.

* But that rally fizzled later in the day, as news of variable quality findings in north central North Dakota emerged from the Wheat Quality Council's tour.

* Harvest potential for the spring wheat crop in north central North Dakota is variable, with fields that were planted in a timely fashion on track for bumper yields, scouts on an annual tour found on Wednesday.

* But fields that were seeded late were expected to come in with below average yields as the crop struggled through early development in muddy fields.

* That news convinced dealers to short wheat and go long on corn, traders said.