Corn Yield Response to Simulated Hail

INSIGHTS

• Hail damage can affect corn yield differently depending on crop growth stage.

• Results from this trial were similar to previous research showing the greatest impact of hail was at tassel and early reproductive stages.

Introduction

Hail damage can be unpredictable, resulting in defoliation and stalk damage that can cause varying levels of yield loss depending on damage severity and timing. While visual assessments of leaf area loss can appear devastating, corn plants can recover quickly in some cases and maintain much of their original yield potential. Plant growth stage at the time of a hail event has the greatest impact on the level of resilience the corn plants will exhibit.

Hail events prior to the V6 growth stage typically have little effect on yield, as the growing point of the corn plant is still protected.1 In early growth stages, leaf whorls may become twisted and bent over from hail damage, making new leaf emergence difficult. Corn yields are increasingly sensitive to hail damage from the V6 stage until tassel, when hail damage can have the greatest impact on corn yield. For example, an 80% reduction in leaf area at the V10 growth stage results in only an 11% reduction of potential yield. The same reduction in leaf area at tasseling can reduce yield potential almost 70% (Table 1).

Table 1. Estimated percent yield loss at different stages and severity of leaf loss caused by hail damage.²

2024 Agronomy in Action Trial

Agronomy in Action research trials were established in Malta, IL, Slater, IA, and Waterloo, NE to simulate leaf area and stalk injury from hail at different crop growth stages and to assess the effect on corn yield. Various tools such as a gas-powered string trimmer were used to simulate leaf shredding and loss. Additionally, stalk bruising was simulated using a golf ball attached to a cable that was spun in a circular pattern while striking stalks. Damage at V3, V6, V12-V15, or R2 growth timings were compared to undamaged treatments (check, Figure 1). Defoliation during the corn vegetative growth stages targeted 90-100% leaf removal while defoliation at R2 growth stage timing attempted to remove 70% of the leaf area at or above the ear leaf.

Figure 1. Pictures of simulated hail damage inflicted on corn plants at V3 (A), V6 (B), V12 (C) and after pollination (D) in 2024 trial.

Trial Results

Trial results in 2024 were very similar to prior research on this topic.² Simulated hail treatments carried out at V3 or V6 timings only resulted in a 7% yield loss. Simulated hail treatments occurring in late vegetative stages caused the most yield loss of 45%. Simulated hail occurring during reproductive (R2) crop stages reduced yields by 24%, which was significantly less than pre-pollination simulated hail (Graph 1). During vegetative growth stages, corn can quickly produce new leaves, helping minimize yield losses. As vegetative growth begins to transition to reproductive functions, corn is no longer able to grow additional leaves and is at a disadvantage for capturing sunlight and carrying out photosynthesis needed to support developing kernels.

Graph 1. Yield response of corn when simulated hail treatment applied at various growth stage timings in 2024 trial.

Summary

Hail events tend to impact yield more than other events. Assessment of the amount of leaf area affected and identification of growth stage at the time of a hail event can help determine possible yield loss. In some cases, fungicide applications may be considered after a hail event to minimize disease development and improve late-season standability. Crop assessment should occur after the plants have had some time to recover to provide better perspective on leaf regrowth and allow a grower to make more accurate management decisions.

Reference

¹Shapiro, C.A., Peterson, T.A. and Flowerday, A.D. 1986. Yield Loss Due to Simulated Hail Damage on Corn: A Comparison of Actual and Predicted Values. Agron. J., 78: 585-589

²United States Department of Agriculture and J.W. Underwood. 2023. Corn Loss Adjustment Standards Handbook. https://www.rma.usda.gov/sites/default/files/handbooks/2024-25080-Corn-Loss-Adjustment-Handbook.pdf