With the increasing acreage of corn in Mississippi and the Midsouth, and since many of Mississippi’s soybean producers are also corn producers, it is fitting that this space be used to pass along significant information about corn production from time to time.

If projected increases in demand for corn come true, continuous corn acreage–i.e., planting corn on the same field for at least 3 years–will inevitably increase. In fact, in a 2009 USDA-ERS REPORT, it is predicted that continuous corn will account for 30% of the total US corn acres by 2015, which somewhat reverses the trend of rotating corn with other crops, mainly soybeans. This figure could be even higher under the biofuel scenario of the Energy Independence and Security Act (EISA) of 2007, which has significantly increased the demand for US corn grain.

It is also predicted that a significant portion of these additional corn acres will be in no-till production.

The above two predictions raise two important points.

●          The so-called “yield drag” or “yield penalty” resulting from corn following corn vs. yield of corn grown in rotation with soybeans is substantiated by results from numerous research projects.

●          Continuous corn production will result in the annual, unbroken production and accumulation of corn residue in fields cropped to continuous corn.

A soon-to-be-published paper (“Agronomy Journal”, Vol. 105, Jan. 2013) by Gentry, Ruffo, and Below at the Univ. of Illinois sheds some light on factors that control the aforementioned yield drag resulting from continuous corn production on a site. Their study was conducted from 2005-2010 on a site that had been in continuous corn or a soybean-corn rotation for the previous 2 years, with the objective of identifying the causes of the continuous corn yield drag relative to the yield of corn from a soybean-corn rotation.

Averaged across all years of their study, yield of continuous corn was about 15% below the yield of corn in the soybean-corn rotation, and this yield drag existed for the duration of the 7-year study. They concluded that the primary causes of the continuous corn yield penalty are nitrogen availability, corn residue accumulation, and weather.

Furthermore, they speculated that the primary agent of the yield penalty in the continuous corn system is accumulated corn residue, which is slow to decompose. This in turn can exert a negative effect on nutrient cycling and speed of N mineralization.

They also proffered that excellent weed control and biotech traits that impart insect resistance in corn make it unlikely that pests are a primary cause of reduced yields in continuous corn systems.

Thus, since weather cannot be controlled and the optimum N rate for continuous corn can only be determined from experience, managing corn residue has the greatest potential for reducing the yield drag associated with continuous corn production on a site.

This implication of accumulating corn residue as a factor in the yield drag associated with a continuous corn production system was addressed in a previously posted blog on MSSOY.

The following excerpt is from that article.

According to Heggenstaller (Pioneer, 2012), “corn residues are a major factor contributing to lower yields for corn following corn compared to corn rotated with soybean, particularly in no-till management.” Major points from this study are:

●          With corn following corn, residue management seems to be the key to avoiding the yield-reducing effects of corn stover. This involves offsetting stover’s potential for producing negative effects by reducing the interference from corn residue through removal (baling) of a portion (approximately one-half) of the stover.

●          Results suggest that corn after corn with stover removal may produce yields that are similar to those from corn rotated with soybeans.

●          No-till continuous corn production is amenable to stover removal due to the high amounts of residue that are produced and remain on the soil surface in the absence of tillage.

●          The amount of corn residue that should remain on a site to maintain soil organic carbon level must be accounted for when considering removal of residue. Click here for an article that provides guidelines regarding the amount of corn stover that should be retained to maintain soil organic matter.

From 2001 to 2012, the Midsouthern states of Arkansas, Louisiana, and Mississippi have seen a significant increase in corn acreage (877,000 to 2,000,000 acres). It is likely that most of these acres are grown in rotation with another crop. However, it is also likely that Midsouth producers would grow continuous corn on some of the acreage if not for the yield drag expected from this practice.

In my opinion, the above findings indicate that Midsouth research that explores a production system of corn following corn vs. corn rotated with soybeans should include assessing the effects of stover removal in the continuous corn system. If findings from this research mimic those from the above studies, then Midsouth producers can elect to grow either continuous corn or rotated corn with no concern for the yield drag associated with growing continuous corn.

Composed by Larry G. Heatherly, Nov. 2012, larryheatherly@bellsouth.net