Corn rose, capping a third straight weekly gain, on speculation that snow and rain during the past two months damaged crops in the U.S., the biggest grower and exporter. About 95 percent of the corn crop was harvested as of Dec.

About 95 percent of the corn crop was harvested as of Dec. 21, the U.S. Department of Agriculture said last month in its final estimate before next week’s annual production report. U.S. output may fall to 12.844 billion bushels, less than the 12.921 billion estimated by the government in December, based on the average of 25 analysts surveyed by Bloomberg News.

“Traders are betting on a smaller crop in next week’s USDA report,” said Don Roose, the president of U.S. Commodities Inc. in West Des Moines, Iowa. “The uncertainty about how USDA handles the crop still left in the field” has reduced the selling interest from both traders and farmers, said Roose, who estimated the crop at 12.886 billion bushels.

Corn futures for March delivery rose 5.5 cents, or 1.3 percent, to $4.23 a bushel on the Chicago Board of Trade. This week, the price climbed 2.1 percent after jumping 20 percent in the fourth quarter.

U.S. inventories before next year’s harvest may fall to 1.608 billion bushels from 1.674 billion bushels last year, based on the average forecast of 24 analysts surveyed by Bloomberg News. That compares with a 1.675 billion-bushel USDA estimate.

Corn is the biggest U.S. crop, valued at $47.4 billion in 2008, government data show.