Emerson Nafziger at the University of Illinois has tagged 2010 as a bad year for corn after corn, at least in the prairie regions in his state. Many farmers there have become accustomed to harvesting equal or better yields on corn after corn as on corn after soybeans, but not this year. He believes the wet spring and slow start may have been part of the issue holding continuous corn back.
Continuous corn was about 35 bushels per acre behind corn yields after soybeans this year in the long-term tillage plots at the Purdue University Agronomy Farm near West Lafayette. The soils are prairie soils, dark, flat with about 4% organic matter. Over the past decade, continuous corn yields trail corn after soybean yields in the plot by only a few bushels per acre, except for in no-till, where the spread is much larger in the 10-year window.
This past year, corn after corn yielded in the mid 180-bushels per acre level, compared to corn after soybeans around 220 bushels per acre. Over a 10-year period, continuous corn trails corn after beans by only 2 bushels per acre in a moldboard system, by 9 bushels in a chisel system, but by 23 bushels per acre in no-till.
For 2010, however, the story is different, notes Tony Vyn, a Purdue University agronomist who now has input into these long-term tillage plots. Moldboard plowing produced the lowest yield in both corn after corn and corn after soybeans, although only by small amounts. In corn after corn, it yielded 184 bushels per acre, compared to 186 for no-till and 187 bushels per acre for chisel-till.
Vyn concluded after this year that no matter what tillage system you're using there is still additional risk in growing corn after corn vs. corn after soybeans. And that's despite all the advances in hybrid genetics, seed treatments, better planting techniques and other moves forward over the past decade.
As Nafziger notes earlier, 2010 wasn't a good year for corn after corn in many locations. While he believes weather explains a lot of the difference, he also believes it may have to do with new corn roots trying to grow where old plants are breaking down. He believes that there may be an effect there that works against the establishment of new corn seedlings in corn after corn situations.