Of all the risks that crop producers in central Illinois contend with during the growing season, weather is often the most unpredictable and costly. Whether it be heavy rains in the spring or intense summer storms, weather can be the difference between a successful and lackluster crop. After these events, producers often ask the same question: what are the impacts on yield? Two studies from 2025 sought to answer that question under two scenarios. The first looks at how waterlogging affects yield potential and nitrogen losses. The second examines how stalk breakage during the growing season reduces yields at harvest. Together, these studies offer useful information and insights that producers can draw on if they experience these issues in their operations.
Wet Conditions and Nitrogen Sources
Heavy rainfall and wet conditions during the planting season are not new in central Illinois. In fact, it happened this year. According to data from the National Weather Service, a total of 6.87 inches of rain fell in April and 2.06 inches in May, with 2.70 inches falling on April 27 alone. Many fields and other low-lying areas saw water pool as the ditches and waterways filled. Excessive rainfall such as this increases the risk of soil erosion and nutrient losses, particularly nitrogen.
Published in the Crop, Forage, and Turfgrass Management journal in 2025, researchers from Ohio conducted trials at two different sites where plots were waterlogged for either four days or no days on corn at the V4 or V6 stage. The researchers evaluated different nitrogen sources, including urea, UAN, polymer-coated urea (PCU), and enhanced-efficiency products. At one of the trial sites, nitrogen content in waterlogged plant leaves decreased by 22% to 38%, depending on the type of fertilizer applied. However, the authors note that while leaf nitrogen levels declined in some cases, overall nitrogen availability alone did not explain yield losses.
When comparing yields, the corn that did not experience waterlogging had approximately 33.5% higher yield than the corn that was waterlogged for 4 days. Additionally, the PCU and enhanced-efficiency urea-treated, non-waterlogged corn had higher yield than the other nitrogen treatments. The difference in yield is attributed to higher kernel numbers and reduced plant losses from waterlogging and erosion. While all nitrogen types increased yields compared to the no-fertilizer control, PCU and enhanced-efficiency urea showed the greatest yield gains. Additionally, when examining the waterlogged yields, standard and enhanced-efficiency urea had similar yields.
The results from this study offer important insights for central Illinois producers. The most important factor is having sufficient nitrogen available early in the growing season, regardless of the type of nitrogen fertilizer used. The study suggests that urea-based products provide more consistent nitrogen than UAN, but the decision about the right form of nitrogen fertilizer should be made at the field level.
Wind Damage and Stalk Breakage
Summer thunderstorms in central Illinois often bring tornadoes, hail, and high winds. For example, in June 2023 and July 2024, derechos swept across Illinois, with many gusts of at least 70 miles per hour being reported at weather stations across central Illinois. High winds often cause corn plants to snap or break at the stalk, especially when the plant has entered the reproductive stages and developed ears.
A research study published in the Agronomy Journal in 2025 by a team of Midwestern researchers evaluated the yield response to above- and below-ear stalk breakage across various growth stages. The growth stages were at V13, V16, and VT, with varying levels of severity: 0%, 25%, 50%, and 75%. Across the various research sites for the study, breakage above the ear resulted in smaller yield losses, but these were not statistically significant. This confirmed previous research that suggested damage to leaves and plant tissue above the ear, while detrimental, did not impact yields. Above-ear damage and breakage did not significantly affect the plant population, kernel weight, or kernel number on the primary ear.
When examining damage below the ear, the study found significant yield impacts across all research sites, with the timing of damage also playing a key role. At 25% severity, the yield loss was around 13%, increasing to 55% at 75% severity. Below-ear damage was also found to affect kernel number, contributing to overall yield losses. Furthermore, the timing and severity of below-ear damage significantly affected the plant population and the number of primary ears. With increased damage to primary ears, the study found that the number of secondary ears increased. Specifically, the number of secondary ears increased with damage severity, and more secondary ears were present the earlier the damage occurred.
For producers in central Illinois, this study reinforces the idea that below-ear breakage has a greater impact on yield than above-ear breakage. Greater damage severity below the ear led to larger yield losses. While second ears can help recover some of the yield loss from primary ears, they cannot make up for all the losses due to below-ear breakage. This information can help guide producers through the complex decisions on crop insurance and how much yield could be lost if a severe weather event causes widespread damage to a corn field.
Weather-related risks are among the most unpredictable and damaging challenges producers face in central Illinois and across the United States. Whether it be tornadoes, hail, flooding, or high winds, these events can make the difference between strong yields and disappointing results. Nevertheless, crop producers need to understand how different weather events and damage can impact their crops and yields.
This blog post examined two studies that evaluated the effects of waterlogging and stalk damage on corn growth and yield. When fields are flooded and waterlogged, nutrient availability to plants is important, with urea-based products tending to provide more consistent nitrogen availability. When stalk damage or breakage occurs above the ear, producers can be assured that yield impacts will be minimal, especially when compared to stalk damage below the ear. While no one can control the weather, understanding how these events affect crop growth can help producers make better decisions and reduce risk.