The U.S. Department of Agri­culture (USDA) raised production estimates for corn and soybeans in its September crop production report last week, surprising farmers and grain traders for the second month in a row.

Based on conditions as of Sept. 1, U.S. corn yields are expected to average 169.9 bushels per acre, up 0.4 bushel from the August forecast. Soybean yields are expected to average 49.9 bushels per acre, up 0.5 bushel from last month.

Lack of heat stress

“You should never be surprised about these late season bumps in soybean numbers,” USDA meteorologist Brad Rippey said, noting the crop benefitted from below average temperatures that prevailed across most of the major U.S. growing areas during August. “Corn may be a little bit more of a surprise, but the bottom line again is we went through an entire season with...