The words ‘final exam’ are likely scary for many, but for corn growers the pre-harvest period is the perfect time to grade themselves on this year’s efforts. Take this opportunity to walk your fields and gain insight on the past year while formulating any plans to correct preventable losses.
Go to various spots in the field and count the number of fully developed ears. Given your planting population, have you achieved 90% effective ear count in that field? If not, this is the time to find out why.
On those plants that do not have an effective ear do you notice anything different about the diameter of the stalk? These plants should be dug to check for root restrictions or other damage. If the stalk diameter and plant-to-plant spacing is normal, examine the ear to see if the issue is related to pollination or kernel abortion. If this is the case, the kernel will have a much different appearance than an ovary that was never pollinated. Issues such as silk clipping or leaf feeding from various insects that were feeding on leaf tissue prior to pollination are possible if pollination did not occur.
Do the rows on the ear remain constant or do you have pinched rows? Pinched rows on the ear would indicate that something likely interfered with the hormonal balance in the plant during the row formation time (around V8-V12) that impacted the plant. It can be as simple as a weather anomaly or it could be the impact of a product that was applied to the meristematic tissue at an inopportune time.
Look at the plants and ears to see if potential nutrient deficiencies have led to kernel abortion. One common deficiency at this time is nitrogen, indicated by an inverted yellowish-orange V that starts at the tip of the lower leaves. Plants that run out of N early can respond by aborting tip kernels and can be more prone to individual death. Go out and take a 12 inch soil sample to test for soil nitrates. If your results come back under 5ppm, you may not have applied enough N. If levels are above 13ppm, you likely have too much N in the soil. The average range for acceptable levels of soil nitrates in a 12 inch sample is anywhere from 5-13ppm. If you see N deficiencies it may be prudent to rethink your timing and method of application to help reduce the likelihood of future losses.