Across much of Iowa, the corn harvest is already underway thanks to a hot summer that caused crops to mature faster than usual. Many farmers are finding wildly varying yields even within the same field. That’s the case with Jones County farmer Myron Ehresman (AIRS-man), who began combining his 1,100 acres of stressed corn near Anamosa on the holiday weekend.

“In some places it’s making 200 bushels (per acre), but on the same row, same variety, not too far away, it might only be making 10,” Ehresman says. “And it seems like those areas where it’s only making 10 to 30 (bushels per acre) are a lot bigger than those areas where it’s making 180 to 200.” The type of soil in which the corn was planted made a big difference in terms of yield.

“There are two different varieties of corn where I’ve combined and they both responded the same. When the soil type changed, they just didn’t have any ears to speak of and it didn’t matter what variety it was,” Ehresman said. Lighter, more sandy soils with less water-holding capacity were baked by July’s heat and drought, according to Ehresman.

The U.D.A.’s weekly crop update is due out later this afternoon.