File this under Ripley's Believe it or Not if you want. It's an actual testimony from a farmer in central Indiana.
He purchased a newer but still used combine over the winter, and first tried it out shelling corn this fall. His non-irrigated fields are mostly soil types that have loam soil or even sandy loam soil over gravel at 30 to 40 inches. This was not a good year to have gravel at 30 to 40 inches below the surface when corn roots were searching for water.
At any rate the first several fields he ran made 5.5 bushels per acre, 6 bushels per acre, then finally 15 bushels per acre. Fortunately, he has crop insurance.
The next day out he was running a field of corn that lies along a major creek, but which has soil types underlain with gravel away from the creek. The soils nearest the waterway are flood plain soils, typically deeper. These were poorly drained soils that hold water. In two or three years out of five, they either drown out or flood out early in the season. This year, they grew corn. These areas often extend out into the field in tongues or irregular shapes. Those farming this ground often call the lowland that extends outward in a narrow finger-like shape slews.
He was combining along, getting his normal 10 to 15 bushels per acre, when suddenly he heard an unfamiliar noise. It was like chattering and clanging. Unfamiliar with the machine, he stopped immediately, fearing something was wrong. He figured he had perhaps thrown off a gathering chain.
All gathering chains were in place. Nothing was wrong with the combine. Suddenly it dawned on him that what he was hearing was corn going through the combine. He had moved into one of the slews yielding over 100 bushels per acre. It was the first time he heard the combine sound like it is supposed to when it is running 'real' corn.
His story may bring a smile to your face, but it also has a point. Yields this year are very much tied to soil type. Soils that hold too much water in a normal year are where you will find your corn this year. High spots, except in areas blessed with rain at the right time, will drag the yield monitor down toward zero, if not all the way to absolute zero. That's how severe the difference is in some fields.