China's corn harvest, the world's second-largest, plunged by a more-than-estimated 13% to a four-year low because of droughts in the main growing regions, according to a report from Bloomberg.

A survey of farmers there shows production dropped to 144.374 million metric tons (5.684 billion bushels) from 165.9 million tons last year, based on interviews completed during harvest. The estimate is below the 155 million tons USDA predicted on Oct. 9 and the 163 million forecast on Oct. 14 by the China National Grain and Oils Information Center.

Crop yields dropped 16%, erasing the benefit of a 4% increase in planted acreage, Bloomberg reports. Drought ravaged 19.8 million acres of farmland.