* Corn drops on plentiful world supplies

* Cheap Brazilian supplies curb gains in Chicago futures

CANBERRA, Feb 22 (Reuters) - Chicago corn futures fell on Thursday to their lowest level since November 2020, as speculators bet on further price drop amid ample supply from top exporters - the United States and Brazil.

Soybeans hovered near a three-year low reached in the previous session due to pressure from cheap Brazilian exports, while wheat fell amid plentiful Russian shipments.

The most-active corn contract on the Chicago Board of Trade (CBOT) was down 0.4% at $4.22-1/2 a bushel, as of 0637 GMT, after falling as low as $4.08-3/4.

Further declines are likely, said Ole Houe at IKON Commodities in Sydney.

"With the weight of the South American crop now coming at us, I think we'll go below $4," he said, though he warned that the huge short position held by investors meant that when a rally does occur, it is likely to be rapid.

Expected rainfall over the next few days in Argentina's Pampas region will likely boost 2023/24 soybean and corn crops there, the Buenos Aires grains exchange said in a report.

Argentina's Rosario grains exchange cut its estimates for the country's 2023/24 soybean and corn harvests, but the 49.5 million metric tons of soy and 57 million tons of corn are still a huge improvement on the previous season.

CBOT soybeans added 0.2% at $11.66-3/4 a bushel, having touched $11.58 on Wednesday, while wheat was down 0.2% at $5.77 a bushel and not far from September's three-year low of $5.40.

Corn, soybeans and wheat have all fallen between 8% and 13% so far this year amid selling by speculative investors who think plentiful supply and falling Chinese demand for animal feed will lead to further losses.

Funds were net sellers again on Wednesday, traders said.

The U.S. Department of Agriculture (USDA) said last week that U.S. ending stocks of soybeans, corn and wheat would rise sharply from a year ago.

Ukrainian farmers are reviewing their planting plans for 2024 after low corn prices led to steep losses last year, but their ability to switch to more profitable soybeans is limited by scarce funding, producers said.

Denmark's farmers on Wednesday voiced concerns that plans to levy a carbon emission tax on farming as part of efforts to meet Denmark's ambitious climate goals would force them to reduce production and close farms.

(Reporting by Peter Hobson; Editing by Sherry Jacob-Phillips)