Corn following corn may be getting its second strike this season, said University of Illinois Extension agronomist Emerson Nafziger.

“Despite different planting season and crop conditions in 2011 than in 2010, we are again hearing that corn following corn is producing lower yields than corn following soybean in many areas,” Nafziger said.  

“In some cases, I’ve heard reports of corn following soybeans yielding in the range of 230 bushels per acre, while corn following corn in the same area planted with similar practices is yielding in the 160 to 170 range. We don’t expect corn following corn to average 60 or 70 bushels less than corn following soybeans over whole areas, but this does illustrate what will again be a significant issue in some fields this year.”

Nafziger said it was easy to attribute last year’s decreased yields in corn following corn to weather. In 2011, he doesn’t have as clear a picture about why growers are seeing this problem again.

What happened this year to result in a second year of substantial yield loss in corn following corn?

Nafziger offers the following:

1.) The spring of 2011 started out well, with some corn planted in early April. Almost all of this was corn following soybeans, given that such fields tend to dry out faster and need less work in the spring. It turned wet and cool after that, and planting stalled at about 10 percent complete through the rest of April. So planting was, on average, late in 2011.

2.) Once the calendar turned to May and it dried up enough for field work, planting got under way in a big rush, with about 60 percent of the crop planted over the first two weeks of May. Many fields planted during this period were wetter than ideal.

And because fields that were in corn the year before almost always dry out more slowly than those that were in soybeans, those who started planting corn following corn in early May planted into even wetter and cooler soils than those planting after soybean.

This not only caused more compaction, “undoing” much of the benefit of tillage last fall, but it also brought issues of residue interference, seed placement, and effects of heavy equipment in many corn-on-corn fields.