Allelopathy--Corn
Since corn is often rotated with soybeans in the Midwest, and is increasingly so in the Midsouth, the effect of possible corn allelopathy on following soybeans is of interest to Midsouth producers. However, there is negligible information to indicate any such effect.
So, this article in my allelopathy series will deal with possible corn allelopathy in general.
● As with extracts from the residues of other crops, extract from corn residue inhibits germination and growth and development of corn seedlings in laboratory experiments (Martin, McCoy, and Dick, Agron. J., Vol. 82, 1990; Elmore and Abendroth). However, there is no indication in the literature that this has been manifested in a field environment.
● Using corn allelopathy is a hoped-for and perceived possible alternative to weed management with synthetic herbicides or herbicide-resistant hybrids (Pratley 2006). This is a worthwhile alternative weed management approach in corn, but as of this date (2012), it has not been successfully accomplished in production environments.
● In field experiments, Elmore and Abendroth state “...yields are reduced when corn follows corn....”, or to use common jargon, there is a “yield drag” for corn following corn. Allelopathy is often implicated but rarely if ever proven in field environments because of weather vagaries, amount and makeup of the residues, and unknown factors such as soil microbial activity. More than likely, allelopathy is used as a catch-all term for the myriad unidentified causes of this proven occurrence.
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.
Additional discussion of possible corn allelopathy is presented by Lykins in the April 2012 issue of Corn and Soybean Digest.
In summary, and to be concise, corn allelopathy has not been specifically identified as a factor in US corn production systems, especially as it relates to soybeans rotated with corn. There is no evidence that corn allelopathy will be utilized as a weed management tool in the near future.
Composed by Larry G. Heatherly, Nov. 2012, larryheatherly@bellsouth.net