As China continues making large corn and soybean purchases from the U.S., markets reacted last week by extending an unusual harvest rally that began in mid-August.

November beans gained more than 30 cents on the week, coming close to matching highs from the previous week in the $10.80 range.

December corn futures started the week just under $3.90 per bushel and reached highs above $4 per bushel by week’s end.

On Oct. 14, the USDA announced an export sale of 420,000 metric tons of U.S. corn to China, which...