All first-year corn had followed soybeans. All second-year corn was s-c-c. I carried the study over to third-year corn...but didn't have enough data for a conclusion.

Some of the best corn I've ever seen was a field that had been in corn for almost 30 years. It was rotated to beans twice c-s-c-s-c and has been in corn since then. The yields are "recovering" but just haven't been the same. There is something to say about countinuous corn in high-yield plots. Warsaw and Childs were onto something!