US corn futures dropped to a 3-1/2 week low on Tuesday while soyabeans fell for the first time in four sessions as largely dry US Midwest weather propelled harvesting, and rains bolstered crop prospects in South America where farmers are planting corn and soya.
Positioning ahead of a monthly US Department of Agriculture (USDA) crop supply and demand report on Friday also weighed on prices as traders anticipated minimal reductions to corn and soya crop outlooks despite poor crop weather this year.
"The harvest is rolling along and farmers are selling. There's no bullish news out there and it's just a slow bleed lower," said commodities broker Craig Turner at Daniels Trading.
CBOT December corn fell 1-1/2 cents to $3.81-3/4 per bushel by 12:18 p.m. CST (1818 GMT) while January soyabeans shed 1-1/4 cents to $9.36-3/4 a bushel.
The USDA said on Monday that 52% of the US corn crop was harvested as of Sunday, slightly behind market forecasts of 54%. Soyabeans were 75% harvested, on par with expectations. US wheat futures rose modestly on Tuesday after the USDA reported slower-than-expected winter crop planting progress.
The agency said 89% of the US winter wheat crop had been planted, behind market expectations of 91%. US wheat prices were capped by stiff competition in global export markets. Major wheat importer Egypt bought French and Russian grain in its latest tender that did not feature any offers of US wheat.
CBOT December wheat futures rose 2-1/2 cents to $5.12-1/4 a bushel, rebounding from a 1.2% drop in the previous session.