GRAINS-Corn slips further after USDA surprises market with supply estimates

By Gus Trompiz and Daphne Zhang

PARIS/BEIJING, Jan 13 (Reuters) - Chicago corn futures edged lower on Tuesday to add to a day-earlier slide as bigger-than-expected supply estimates from the U.S. Department of Agriculture hung over the market.

Soybeans and wheat also extended losses from Monday as the USDA's widely tracked data also weighed.

The most-active corn contract Cv1 on the Chicago Board of Trade (CBOT) was down 0.6% at $4.19 a bushel to remain around its lowest since late October. The benchmark plunged 5.4% on Monday following the USDA's data.

The agency wrong-footed the corn market 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.

"Funds clearly dumped corn as the U.S. supply and demand turned very heavy and U.S. corn now needs to stimulate demand or discourage acres for 2026/27," CM Navigator analyst Donatas Jankauskas said in a note.

Corn had been supported in recent weeks by brisk U.S. exports and expectations that the USDA would trim its harvest view.

CBOT soybeans Sv1 eased 0.6% to $10.42-1/2 a bushel to trade at their lowest in over a week. CBOT wheat Wv1 inched down 0.2% to $5.10 a bushel.

The government data also pressured the soybean market, with the USDA increasing its U.S. harvest estimate and reducing its U.S. export forecast. That dented recent optimism over a resumption in Chinese purchases of U.S. soybeans under a bilateral trade truce agreed in late October.

Wheat prices were curbed by the USDA's estimate of U.S. winter wheat acreage for 2026, which while showing a decrease from last year exceeded an average of analyst estimates.

The wheat market is already grappling with abundant supply in major exporting countries, while the soybean sector is bracing for an expected record Brazilian soybean crop.

"While the USDA's adventures in the U.S. corn balance sheet were a genuine curveball for the market, the fact remains that global (grain and oilseed) markets are oversupplied – in an immediate, as well as a structural, sense," Rabobank analysts said.