Agriculture prices fell by 3% in December, the seventh decrease over the past eight months, due to improved supply prospects and weak demand, the World Bank said.

Wheat prices declined 4.3% as large plantings and favorable weather conditions in the U.S. looked set to increase global supplies, the World Bank said late Friday, while corn prices fell 5.7% due to weak animal-feed demand and lower demand for ethanol.

Cocoa plummeted 13% to a three-year low as continued weak demand and a large West African crop took its toll, the World Bank said, while arabica coffee prices fell 3.4% due to a likely production surplus in 2011-12 because of record crops in Brazil and Vietnam.

Sugar prices decreased 4.1% as harvests for most major producers in the northern hemisphere progressed well, pointing to a significant global surplus, while cotton prices dropped 8.9% due to weak demand and a better-than-expected 2011-12 crop.

Rice prices reversed a seven-month upward trend, the World Bank said, falling 4.8% after India announced the removal of its export ban on common-grade rice and on better supply prospects elsewhere in the region.

The World Bank added that agriculture prices have continued to fall in early January as last week's U.S. Department of Agriculture reports showed improved global supply conditions.

-By Michael Haddon, Dow Jones Newswires; 4420-7842-9289; michael.haddon@dowjones.com

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January 16, 2012 04:35 ET (09:35 GMT)