Especially during the reproductive stages of soybean growth, inadequate water supply and late-season drought stress can significantly impact yield potential. Throw high temperatures into the mix, and you’ve got a perfect storm of problems. You can’t predict the weather, but you can make choices that can help reduce plant stress and guard against losses caused by unpredictable weather you may face throughout the season.
Effect of heat and soybean drought stress on yield
Soybeans that experience drought during the flowering stage can have yield reductions up to 55%. Yield reductions from drought during grain-filling can reach nearly 60%.¹
Typically, when temperatures exceed 85 F, especially over a span of several days, soybeans are at risk for heat stress.
Soybean water requirements
Soybean water requirements peak when a full canopy forms. This typically coincides with the reproductive growth stages, including pod elongation (R4), early pod fill (R5), and mid-pod fill (R5-R6). On average, the R4 through R6 growth stages require almost double the water used in earlier growth stages. Additionally, limited soil-water supply and high heat stress can cause aborted flowers, aborted small pods, aborted seeds in larger pods and production of smaller seeds.
Optimal water supply during these stages is critical to achieve the highest grain yield, so if irrigation is available in your fields, make sure you are sufficiently irrigating your crop during these stages.
Soybean water usage chart
Symptoms of soybean drought stress
- Stunted vegetative growth: Before the leaf flipping symptom (see below) becomes apparent, you may notice dry soybean plants are undersized.
- Leaf flipping: Drought conditions cause soybean leaves to flip upside down, exposing their silvery undersides, which reflects more light, lowers leaf temperature, and reduces the amount of moisture lost.
- Leaf curling/clamping: In severe drought conditions, leaf curling/clamping helps conserve water by reducing the amount of leaf area exposed to the sun. Leaf trifoliates close, clamping the center leaflet between the outside leaflets, hindering further growth and productivity.²
How to prevent and manage heat and drought stress in soybeans
Mitigating the damage of heat and drought stress in soybeans involves a mix of preventive measures and in-season management practices.
Select stress-tolerant soybean varieties
In areas where drought stress is common, consider selecting seed that has been developed to tolerate drought and remain productive under stress.
Select seeds that work with earlier planting schedules, as early planting is another tactic to help prevent yield loss from drought stress.
Plant early to avoid soybean drought stress
Early-planted soybeans typically develop deeper root systems before hot, dry weather hits, allowing for more effective subsoil moisture absorption.
Narrow rows also help the crop canopy close sooner, shading the soil surface and reducing soil moisture loss due to evaporation.
Reduce other soybean stressors
Reducing other types of stress, whether from disease, weeds or pests, can help your crop navigate a drought scenario.
Managing early-planted soybeans with successful pre-emergence herbicide can promote earlier canopy closure. Canopy closure helps dry soybean plants outlast drought conditions by reducing soil surface evaporation, leaving more water available for photosynthesis.
Additionally, using a fungicide like Priaxor®, a product that received the Plant Health label from the EPA, can provide benefits beyond disease control, including improved plant tolerance to yield-robbing environmental stresses. Plant Health benefits include stress tolerance and growth efficiency and disease control from the bottom up, helping soybeans stay greener longer by preserving bottom leaves, maintaining middle leaf growth and conserving top leaves.
To learn more about mitigating soybean stressors, reach out to your seed retailer, a nearby extension office agent or a professional like your regional BASF representative.
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Endnotes
- Wang, Cheng, et al. “Drought and Rewatering Effects on Soybean Photosynthesis, Physiology and Yield.” PMC Home, 3 July 2025, pmc.ncbi.nlm.nih.gov/articles/PMC12229149/. Accessed 21 May 2026.
- Ciampitti, Ignacio, et al. “Drought and heat stress impacts on soybeans in Kansas.” Agronomy eUpdates. 24 Aug. 2023, eupdate.agronomy.ksu.edu/article/drought-and-heat-stress-impacts-on-soybeans-in-kansas-559-1.
