It’s important to understand the yield-limiting effects of heat and drought on corn, especially at the critical pollination stage. Learn what to look for if your corn is experiencing heat stress and drought and how to manage drought-damaged corn fields.
What temperature can corn plants tolerate?
If temperatures surpass 95 F, corn growth is slowed, and yield can be reduced by 1.5 bushels per acre for each day the temperature remains at that temperature, or higher, during pollination and grainfill.¹
Yield impacts of drought stress in corn
When drought stress occurs for four or more consecutive days, growers can calculate yield loss per day using the following percentages:
- VE to V12 (early vegetative growth): 1% to 3% loss per day
- V12 to VT (late vegetative growth): 2% to 5% loss per day
- R2 (pollination to blister): 3% to 9% loss per day
- R3 (milk): 3% to 6% loss per day
- R4 (dough): 3% to 5% loss per day
- R5 (dent): 2% to 4% loss per day
- R6 (physiological maturity): 0% loss per day²
Corn is most susceptible to yield-reducing damage if heat and drought occur from pollination (VT) to the blister stage (R2).
Drought stress accelerates pollen shed but delays silk elongation. If pollen shed precedes silk emergence, pollination timing will be critically affected. Plus, once temperatures exceed 95 F (especially with relatively low humidity) pollen is no longer viable and silks become desiccated and unreceptive to pollen, impeding pollination.
Even if temperatures remain favorable during pollination, proper grain fill requires adequate moisture during R3 when the first small, watery kernels form.
How much water does corn need each day?
Corn needs approximately 0.3" of water per day during the early reproductive stages. Air temperature, humidity and cloud cover can impact the total amount of available daily soil moisture.³
Corn drought stress symptoms
- Leaf rolling/onion leafing: The earlier in the day leaf rolling occurs and the longer leaves remain rolled, the more likely yield loss will occur.
- Leaf discoloration: In severe drought conditions, leaf tissue may appear grayish or tan.
- Reduced ear size or ear abnormalities: Reduced ear diameter, ear length and abnormalities like banana ears (curvature of the cob) or zipper ears (missing kernel rows in ears).
- Reduced kernel count: Drought and high temperatures can lead to poor or sporadic kernel set in the ear.
- Ear tip back: Late-season moisture stress after pollination can cause kernels at the tip of the cob to die back.
How to manage heat and drought stress in corn
Corn can recover from drought damage, and if pollination appears to be mostly successful, you can manage and harvest the field as normal.
However, if pollination appears to be inconsistent due to drought conditions, consider a salvage harvest for silage. If corn plants do not show ear development, are losing leaves and leaves are not unrolling at night, the yield potential will likely be zero to 50 bushels per acre.⁴ A last resort is harvesting silage to avoid total profit loss.
Harvesting drought stressed corn is typically worthwhile; however, chopping costs and labor may outweigh the profit in severely stressed fields. Understanding silage pricing can help you decide whether a salvage harvest is best for your situation.
To lessen the impact of heat stress or drought on yield potential:
- Reduce other stressors to your crop, including common disease threats or pest-related stress.
- If available, irrigate in extreme heat conditions (especially if corn is already under other stressors that could delay silk emergence).
- If your area is susceptible to frequent drought and heat stress, look for drought-resistant hybrids and corn seed treatments to boost vigor.
Experts are available to help you make your decisions. Reach out to your seed retailer, a nearby extension office agent or a seed company professional like your regional BASF representative.
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Endnotes
- “Drought Status Update for the Midwest U.S.” Drought.gov, 19 Oct. 2023, www.drought.gov/drought-status-updates/drought-status-update-midwest-us-2023-10-19. Accessed 3 May 2024.
- Thomison, Peter. “Hot, Dry Conditions Stressing Corn.” Agronomic Crops Network, 2022, agcrops.osu.edu/newsletter/corn-newsletter/hot-dry-conditions-stressing-corn. Accessed 3 May 2024.
- Quinn, Dan. “Heat Stress And Drought Considerations For Corn.” Pest&Crop Newsletter, 21 June 2022, extension.entm.purdue.edu/newsletters/pestandcrop/article/heat-stress-and-drought-considerations-for-corn/. Accessed 3 May 2024.
- Brackenrich, Justin, and Gregory W. Roth. “Managing Drought Stressed Corn.” Penn State Extension, 11 Oct. 2023, extension.psu.edu/managing-drought-stressed-corn. Accessed 25 May 2026.
