US corn futures rose to a 3-1/2-week high on Friday as China booked its largest purchase of the grain in more than 5 years and as flooding in the western US Midwest raised concerns over spring planting. Technical selling and profit-taking later pulled corn from the highs, although the market closed with a second straight weekly gain.
Soyabeans fell for the first time in three sessions on worries over demand for ample US supplies as Brazilian farmers are harvesting a bumper crop.
Wheat futures drifted lower in a profit-taking pullback from earlier 3-1/2 week highs.
The US Department of Agriculture announced corn sales totaling 300,000 tonnes to China on Friday following weeks of rumors that Beijing was poised to make a goodwill purchase of the grain amid ongoing US-China trade talks.
Grains futures were anchored by a broader commodities market selloff and as a firming US dollar, particularly against the currencies of rival exporters Brazil and Argentina, stoked concerns about US export demand.
Flooding in the western US Midwest remained a focus for grains markets as large swathes of Iowa and Nebraska - two of the top three corn-producing states - are under water.
The USDA is due to release its annual planting prospects report next Friday.
A farmer survey by crop advisory firm Farm Futures on Friday said US growers will plant 1.9 percent more corn acres this year and 3.7 percent less soyabeans.
Chicago Board of Trade May corn futures settled up 2 cents at $3.78-1/4 a bushel, ending 1.3 percent higher on the week.
May soyabeans were down 6-3/4 cents at $9.03-3/4 a bushel. The 0.6 percent weekly decline was its third drop in four weeks.
CBOT May wheat ended down 1/2 cent at $4.66 a bushel after earlier hitting a 3-1/2 week high of $4.73-3/4. The contract closed the week up 0.8 percent, its second straight weekly advance after falling in the previous five weeks.