Incomplete Kernel Set and Tipped-Back Corn: How Do They Differ?

Field Corn

Crop tours in Ohio have indicated that crop pollination was generally good, but kernel abortion was noted in some fields. It is important to recognize that both affect final corn yields. Similarly, it is relevant to understand when/how issues occur (e.g., pollination issues vs. kernel abortion). The result is the same: fewer viable kernels per ear, but diagnosing the difference helps understand and identify the potential associated causes.

Corn plant with kernels exposed

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Incomplete kernel set
Poor or scattered kernel set in the ear (Fig. 1). Poor or scattered kernel set on ears results from either failed pollination/fertilization of ovules (VT or R1) or abortion of young kernels during the several weeks after pollination (R1–R3).

 Incomplete kernel set at varying degrees from least to most right
Figure 1.
Ears displaying incomplete kernel set at varying degrees from least (left) to most (right).

Possible causal factors: Silks damage (e.g., insect feeding and silk clipping), stress due to drought and high temperatures, pollination issues (e.g., asynchronous pollen shed and silking, inadequate pollen supply), phosphorus deficiency, herbicide injury, and cloudy days (due to low photosynthetic capacity).   

Postulated development timing: Pollination, VT or R1; and early reproductive stages, R1–R3.

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Tipped-back ears
Missing kernels at the tip of the ear (Fig. 2). Tipped-back ears can include failed pollination or kernel abortion at the ear tip and progressing down to varying severities. Tip-back ears are also referred to as tip-dieback, nosing, or tipping back. The nose or tip back in a corn ear can be the result of different conditions—a plant population response (i.e., higher seeding rates, more interplant competition, failure of pollination of ovules in the ear tip) and weather after pollination (i.e., non-favorable conditions, inadequate photosynthate supply, kernel abortion). Unfertilized ovules and aborted kernels may appear dried up and shrunken, but aborted kernels often have a slight reddish or yellowish color. In a corn ear, pollination/fertilization starts from the base and ends on the ear tip. Hence, kernels that develop on the tip of the ear are particularly vulnerable or susceptible to abortion as they form last (if they form at all).

Lack of pollination in the very tip
Figure 2. Tip back ear in corn displaying lack of pollination in the very tip (whiteish color) and kernel abortion during grain filling period below the tip (reddish or yellowish color).

Possible causal factors: Pollen and silk availability, kernel abortion, heat/drought stress, genetics, higher seeding rates, nitrogen deficiency, foliar diseases, and cloudy days.

Postulated development timing: Pollination, VT or R1; and early reproductive stages, R1–R3.

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Management Considerations

Follow recommended guidelines for minimizing crop stress for incomplete kernel set (Fig. 1) and tipped-back ears (Fig.2). This includes (but is not limited to) maintaining appropriate fertility, adjusting planting depth with varying soil conditions, following recommended herbicide application dates/rates, selecting adapted hybrids and seeding rates consistent for yield potential and planting dates, avoiding planting too early in wet/cold soils, and minimizing weed competition with effective herbicide applications and/or timely cultivation.

Ears exhibiting tip back may not always be cause for concern. Favorable growing conditions may result in more potential kernels per row than usual. So even if corn ear tips are not filled entirely due to poor pollination or kernel abortion, yield potential may not be affected significantly, if at all, because the number of kernels per row may still be above normal. On the other end, a general rule of thumb can be that presence of ears consistently filled to the very tip may indicate that a higher plant population might have been needed to optimize corn yields.

Resources

Ortez, O. A., McMechan, A. J., Hoegemeyer, T., Ciampitti, I. A., Nielsen, R., Thomison, P. R., & Elmore, R. W. (2022). Abnormal ear development in corn: A review. Agronomy Journal, 114, 1168– 1183. https://doi.org/10.1002/agj2.20986.

Incomplete Kernel Set – Whole Ear: https://u.osu.edu/mastercorn/incomplete-kernel-set/.

Tip Dieback (also referred to as “tip-back”, or “nosing or tipping back”): https://u.osu.edu/mastercorn/tip-dieback/.

Crop Observation and Recommendation Network

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.