GRAINS-Corn sinks to 3-month low after USDA surprises market with supply estimates

By Karl Plume

CHICAGO, Jan 13 (Reuters) - U.S. corn futures slid to a fresh three-month low on Tuesday, extending prior-day declines triggered by the U.S. Department of Agriculture's outlook for massive supplies following a record-large U.S. harvest.

Soybeans touched a 2-1/2 month low after the USDA on Monday trimmed its U.S. export view and raised its harvest estimate for rival supplier Brazil, while what futures followed corn and soybeans lower.

The USDA on Monday caught the corn market wrong-footed by increasing its estimate of the 2025 U.S. harvest to a new record, contrary to expectations of a downward revision, while also pegging U.S. quarterly stocks of the cereal at their largest ever.

Losses on Tuesday were tempered by bargain buying and technical support, and as traders turned their focus to weather in Brazil, where farmers will soon be planting their large second corn crop.

"For corn, this was a rip-the-Band-Aid-off event and these are probably the worst numbers we're going to see. If anything, there is some risk on South American weather," said Ted Seifried, chief strategist at Zaner Group.

"But for soybeans, I don't feel like it's the same sort of mentality," he said.

Brazil's record-large harvest is likely to undercut demand for U.S. soy in the coming months, and it remains unclear if a recent surge in U.S. purchases by China will continue after a 12-million-metric-ton buying target is achieved.

Chicago Board of Trade March corn CH26 was down 1 cent at $4.20-1/2 a bushel at 12:54 p.m. CST (1854 GMT) after earlier touching the lowest point for a most-active contract Cv1 since October 16. March soybeans SH26 were down 10-1/2 cents at $10.38-1/2 a bushel, the lowest since October 23. CBOT March wheat WH26 was down 3/4 cent at $5.10-1/2 a bushel.