Factors affecting crop production include genetics, environment, and management practices (G × E × M interactions). Environmental conditions across regions vary on spatial and temporal scales (Figure 1). It is important to assess how corn growth and yield can be affected by long-term weather patterns (approximately seven to 10 days) such as heat and drought, solar radiation and light availability, and variable heat unit accumulation over the crop season.
As climatic conditions continue to shift, weather variations at the different growth stages of corn can affect the crop’s productivity in a positive or negative way. This article reviews the potential effects of these conditions and introduces opportunities to address these challenges through management decisions.
Drought and High Temperatures
An increased frequency of drought events has been associated with climate change. Drought conditions are predicted to become more severe and impact more areas. Rainfall may also become more erratic in the future as temperatures continue to increase, leading to variable soil moisture across the midwestern United States (Crimmins et al., 2023). Corn yields can be heavily affected by drought; among cereals, corn is one of the most sensitive crops. Simulations have suggested that droughts will coincide with more frequent hot extremes in the future.
Weather extremes, particularly drought and heat, pose significant challenges to farmers and growers worldwide and to corn prices and crop security. Seasonal air temperatures and precipitation may explain about 30% or more of the year-to-year variability of crop yields in the largest crops, including corn. Corn has shown a negative yield response to higher air temperatures. These lower yields have been offset (at least partially) by introducing new genetics, agronomic strategies, and technologies. In Table 1, we highlight agronomic decisions that could be used to lessen the effects of drought and high temperatures in corn production.
Solar Radiation and Light Interception
Solar radiation and light interception directly impact crop production. Solar radiation intercepted by the crop canopy is a key factor driving crop development. Solar radiation drives crop photosynthesis (i.e., photosynthetically active radiation), the accumulation and movement of photosynthetic products, the formation of plant organs, transpiration, and crop yield. Corn’s biomass production is a result of the amount of solar radiation intercepted by the plant and the plant’s photosynthetic outcomes. Similarly, grain yield is proportional to the amount of biomass.
Two factors are important when it comes to radiation: available radiation and available radiation intercepted by the crop. In the absence of environmental stress (e.g., drought, pest pressure, and nutrient deficiencies), research has shown a positive relationship between corn yield and the total amount of solar radiation intercepted by the crop. It has been suggested that improvements in radiation-use efficiency over the past 100 years have translated into small increases of grain yield per unit of area per year.
The impact of short-term occlusion of light is variable in space and time, and it can affect crop yields. Short-term changes to light availability can result from dust storms (e.g., wind erosion), which have been evident in the United States since the Dust Bowl of the 1930s. Dust storm events have also been observed recently in states such as Iowa, Kansas, Nebraska, Minnesota, and the Dakotas. These events cause temporary reductions in light availability and tend to pass quickly, though they may leave dust deposits on plant tissue. Yield reductions from these events can come from losses of leaf tissue, reductions in stands (e.g., stalk breakage), or topsoil erosion.
Another factor affecting corn yield is long-term reduced solar radiation due to conditions such as cloud cover and/or smoke for longer periods of time. This has been studied with shading experiments. Significant yield reductions have been observed as having a negative linear relationship between reduced solar radiation and grain yield. Yield reductions caused by reduced solar radiation are dependent on when solar radiation reduction occurs during the growing season. Studies suggest that solar radiation reductions during corn’s silking and grain-filling stages have more impact on yield than similar solar radiation reductions during corn’s vegetative growth stages earlier in the season. While some management decisions can be used for partial mitigation of variability in solar radiation (Table 1), challenges associated with implementation exist and should be understood.
Heat Unit Accumulation
The growth of a corn plant is directly related to its accumulation of heat units over time rather than its number of calendar days from planting. The corn growing degree day (GDD) system provides information for estimating crop stages and phenology (e.g., tasseling and maturity), given site-specific conditions (e.g., daily temperatures) throughout the season and planting dates. Heat unit accumulation varies depending on temperatures changes; it impacts corn growth and development, and subsequently, crop yields.
A 2012 study reported an increase in the mean annual nonfrozen season of 0.189 days per year for the northern hemisphere, mostly driven by an earlier onset of spring by 0.149 days per year. Additionally, the day of the Midwest’s first autumn freeze has shifted to later, and autumn temperatures have remained higher. The frost-free thermal time in the Midwest has been increasing by as much as 0.3% per year since 1950, resulting in a 16-day increase in this period. This increase is calculated using the Midwestern Regional Climate Center’s Freeze Date Tool, which provides trends for spring and fall frost dates and the growing season length.
When the last spring frost occurs early, it calculates the time needed for the soil to warm so crop planting can proceed with a lower risk of poor or delayed seedling emergence. As soil warms and early planting becomes feasible, growers can use mid- or late-maturing hybrids with extended grain-filling periods to achieve greater grain yields. Previous research indicates possible benefits from adjusting comparative relative maturity (CRM) selection based on the planting date (e.g., delayed planting dates can benefit from shorter corn-relative maturities), but the interaction between planting date and CRM can be variable across environments.
In most parts of the United States, average temperatures later in the season have increased by approximately 1.8 degrees Fahrenheit over the past 50 years. Warm temperatures during the night increase respiration rates and may negatively impact productivity. The greater concern with increasing temperatures is the effect on the crop’s relative growth rate and how the daily radiation energy available per heat unit accumulated, also known as the photothermal quotient (PTQ), may be impacted. A greater PTQ during later vegetative stages is often favorable for yield because more photons per heat unit effectively increase the leaf's potential for carbon reactions in photosynthesis. Achieving maturity in fewer calendar days due to higher temperatures negatively affects the PTQ and may limit the number of days that plants can absorb photons to conduct photosynthesis. However, weather changes, such as extended periods for the growing season and improved solar brightening, also have the potential to bring benefits. Research from the midwestern United States and Europe suggests that certain changes in seasonality may improve crop yields in the future. While these trends have been documented, management decisions have the opportunity to impact or mitigate some of these changes (Table 1).
Management of Stressors: Summary
Management tools can help decision-makers and farmers mitigate the potential negative effects of long-term weather patterns. Some of these tools include varying the relative maturities of hybrids, using drought-tolerant hybrids that outperform standard hybrids in drought conditions, using conservation tillage options, using controlled drainage structures, adjusting seeding rates depending on site-specific conditions, and leveraging the season length by adjusting planting dates.
While genetic improvements are considered major contributors to grain yield, agronomic improvements and climate also play significant roles in corn yield gains. Heat and drought conditions negatively affect crop yields but changes like improved solar brightening can increase yield potential. Moreover, modest increases in temperatures can increase growing degree day accumulation, which positively affects crop growth, development, and yields.
The shift toward longer growing seasons provides corn growers, particularly in northern United States production systems, with an opportunity to increase yield and profits by selecting hybrids with later relative maturities or greater growing degree day requirements. A best-case scenario is to maximize the utilization of relatively short growing seasons (compared to those in southern states) by matching optimal hybrid maturities with optimum planting dates.
Table 1 summarizes these strategies based on the three long-term stress sources discussed in this fact sheet. Table 1 also presents management options to mitigate effects. As with anything, each strategy has drawbacks. These drawbacks are discussed in the “challenge with implementation” column. We are posed with many challenges; proactive planning can help mitigate some of these while protecting or preserving future crop yields. Weather stress conditions cannot be prevented, but negative plant responses may be mitigated.
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References
Crimmins, A. R., Avery, C. W., Easterling, D. R., Kunkel, K.E., Stewart, B. C., & Maycock, T. K. (2023). Fifth National Climate Assessment. U.S. Global Change Research Program.
nca2023.globalchange.gov/downloads
Ortez, O. A., Lindsey, A. J., Thomison, P. R., Coulter, J. A, Singh, M. P., Carrijo, D. R., Quinn, D. J., Licht, M. A., & Bastos, L. (2023). Corn response to long-term seasonal weather stressors: A review. Crop Science, 63(6), 3210–3235.
doi.org/10.1002/csc2.21101