Corn Pollination: The Physiological Fork in The Road

BY Dairyland Seed Agronomy Team

The corn crop is approaching pollination season, which brings us upon a major fork in the winding road to yield. During a season of normal rainfall, we pass this intersection without notice; like an unmarked two-track dirt road off the side of a four-lane highway. In dry conditions, this intersection is well signed, and the road is bumpy in both directions. Pollination success is possibly the most binary event of the season. It either works and we are on the road to success, or we are sent down the road to despair.

This partially pollinated ear demonstrates the habit of silk emergence from the ear shoot. The first silks to emerge have already been pollinated, detached from their kernels, and fell from the ear.

Having already determined the potential number of ears per acre at planting and emergence, and the potential number of kernels per ear during the past few weeks, the plants must now turn ovules (potential kernels) into embryos (actual kernels) during pollination. The R1 growth stage is initiated by silk emergence from the ear shoot. Each silk is attached to a single ovule with the purpose of “catching” pollen and providing a physical pathway for fertilization to occur. Silks begin to elongate 10 to 14 days prior to R1. Once emerged, silks will continue to grow for about 5 days, or until fertilized. The 5-to-8-day pollen shed window must overlap with receptive silks. This synchronization is referred to as the “nick.” Moisture stress during silk elongation can delay silk emergence and sometimes cause the crop to miss the nick (the proverbial fork in the road).

Leading up R1 the crop is using 0.28 inches of water per day. During R1, it increases to 0.30. That’s a scary statistic this season, but the good news is that our corn crop is hard wired for survival and reproduction. The crop adjusts to conditions along the way in the name of survival; this usually reduces yield, but hopefully leaves us surprised with more than expected in the bin. If you have access to irrigation, the solution is simple: use it! Without, we can only hope and pray. Either way, there are observations that we should be making to set expectations and adjust our management.

Now is a good time to begin seeing the yield potential in your crop. Look for the following:

Assess your population of good plants. Another look doesn’t hurt.
Stress from V6 through tassel can alter the number of kernel rows on an ear. Peel husks to see how your crop fared during this period in 2023. Look for 14, 16 or 18 rows in most hybrids.
Note plant height.
Try to observe the nick: look for exposed silks with actively shedding pollen early in the morning or in the evening.
Evaluate pollination success. Brown silks and dead tassels indicate the completion of pollination. Carefully peel husks from ears and gently shake silks free. Any silks that still cling to the ear (see photo) indicate an ovule that failed to pollinate.

Overall, the impacts of stress in 2023 will result in variability across the farm. Arm yourself with current knowledge of your acres as we enter the next part of the yield equation: grain fill. The season is not over and there are still decisions to be made!