Each year as anticipation mounts for finally getting behind the wheel of the combine, work benches, dinner tables and agronomist office desks fill with corn ears. This year is no exception. Examining corn ears before harvest helps paint the picture of how the plant was impacted throughout the year. It may also explain why your yields aren’t as good as you hoped.
One of the biggest concerns observed on corn ears examined in 2022 is “tip back.” Many corn ears did not fill kernels from the base of the ear all the way to the tip. Thus, ear tips exhibited some length of missing and/or incomplete kernels.
There are two main reasons for tip back:
- poor pollination, causing the absence of kernel formation
- kernel abortion
First, it is important to remember that silks that emerge last from an ear during pollination and kernels that fill last during grain fill are located on the tip of the ear. Any significant stresses exhibited shortly before pollination, during pollination and shortly after pollination can negatively impact these “youngest” kernels.
If many ears exhibited tip back, the next step should be examining tips closely to understand the cause. Poor pollination can happen when stressful conditions occur a few weeks prior to and during pollination, when silk and tassel emergence is underway. For example, drought conditions can delay silk emergence and cause poor synchrony between pollen drop and silk emergence.
In addition, since the last emerging silks are located at the tip of the ear, pollen drop, which occurs for only seven to 10 days, can be completed prior to silk emergence. This can cause ovules at the tip, which are potential kernels, to never be pollinated.
Kernel abortion can be identified by shrunken and shriveled kernels on the tip. Kernel abortion is mainly caused by stresses that reduce plant photosynthetic output, such as drought, hail damage, nutrient deficiencies and foliar disease. It’s a problem if these occur during the first several weeks following pollination and through the R3 or milk growth stage. Even consecutive days of cloudy weather can reduce plant photosynthesis enough to cause kernel abortion.
Overall, any plant stresses that limit photosynthetically active leaf area or the photosynthetic “factory” of the corn plant can cause tip fill problems.
For example, the June drought conditions observed in certain areas of Indiana this year, which coincided with the rapid growth phase of corn, limited total plant photosynthetic output or the total “factory” needed for grain fill.
Now, is all tip back bad? No, not always. For example, in certain years, ideal environmental conditions present during corn ear size formation may cause ear size to be larger than normal. Kernel row number is decided from the V6 to V8 growth stage, and kernel number per row is set from V6 to a few weeks prior to pollination. Excellent growth conditions may cause tip back to appear.
Therefore, if tip back is observed, it’s still important to examine total kernel numbers per ear to understand the extent of potential yield impact. In this case, you may still harvest high yields.
Quinn is a Purdue Extension corn specialist. Email him at firstname.lastname@example.org.