August 11, 2010
Tipping Back and Premature Denting
Some corn is showing considerable tipping back. (If there is no tipping back, that usually means that a higher population would have resulted in higher yield.) Some corn is also already showing denting of the kernels, but the kernels are only in the early dough stage.
Once the ears reach the R2 (blister) stage of development, if the plant is stressed and starts to become less optimistic, kernel abortion will occur from the tip back. Kernel abortion will continue to the end of R3 (milk) if stress is present. Once the plants are into the R4 (dough) stage of development, the only adjustment the plant can make is to the kernel size; the early denting is an indicator that the plants are continuing to be less optimistic and are adjusting kernel size down, which will result in lighter kernels at harvest.
What is causing this stress? It may be the heat, but if the plants are running out of nutrients (nitrogen?) that is a definite possibility. However, if roots are very poor, rotted, or damaged by insects, that, too, can cause the plants to experience lack of water and/or nutrients and cause the plants to retrench. In a different year, drought could also cause this.
Yields can still be very good in fields with tipping back and premature denting, but the top of the yield has been lost.
FOR YOUR CALENDAR
Northeast Iowa Research and Demonstration Farm, Nashua
Fall Field Day on August 26, 2010, 1:00 p.m.
Details are posted at http://www.extension.iastate.edu/Pages/eccrops/meetnerf.html.
Southeast Iowa Research and Demonstration Farm, Crawfordsville
Fall Field Day on September 15, 2010
Tentatively there will be a manure application field day in the morning followed by a more traditional field day in the afternoon. More details will be posted at http://www.extension.iastate.edu/Pages/eccrops/meetserc.html.
If you have any questions, please feel free to contact the Iowa State University Extension Office.
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