Project Objectives

Results

Final Results

Plant height, NDVI, and crop biomass, on the other hand, were significantly impacted by the simulated hail timing and severity in all crops. Effect of hail severity on plant height differed depending on the timing of hail simulation as indicated by significant interaction between hail timing and severity.

In case of wheat, reduction in plant height was more severe for hail damage at early (11 and 15 cm for light and heavy damage, respectively) and mid (11 and 14 cm for light and heavy damage, respectively) growth stages than hail damage at late growth stage (2 and 5 cm for light and heavy damage, respectively) relative to untreated control (Figure 2).

Reduction in plant height relative to untreated control for field pea and dry bean was more sever for hail damage during middle and late stages compared to hail damage during early stage.

Similar to plant height, reduction in NDVI due to hail damage relative to untreated control in wheat was higher for the early hail damage (12 and 19% for light and heavy damage, respectively) compared to the hail damage at the middle (7 and 10% for light and heavy damage, respectively) and late (5 and 8% for light and heavy damage, respectively) stages (Figure 3). For field pea and dry beans, NDVI was significantly lower for hail damage at early stage compared to middle and late stages.

Figure 2: Effect of simulated hail damage at the three severity levels and three crop growth stages on the plant height.	Figure 3: Effect of simulated hail damage at the three severity levels on normalized difference vegetation index (NDVI) for wheat, dry beans, and field peas.

Crop biomass of wheat decreased relative to the untreated control, by 22% and 30% in case of light and heavy damage. Wheat biomass was significantly lower for hail damage at early and middle stages compared to the late stage (Figure 4).

Crop biomass decreased by 31% and 38% for field pea, and 36% and 47% for dry bean in case of light and heavy damage relative to the untreated control, respectively. There was a trend of lesser crop damage in wheat due to simulated hail compared to pulses. This difference in wheat may be related to differences in the physiological nature of the stems and foliage, canopy architecture, and planting density.

There was a significant decrease in seed yield of wheat, field pea and dry beans due to hail timing and severity.

Figure 4: Effect of simulated hail damage at the three severity levels on crop biomass of wheat.

Reduction in yield due to hail damage at the early growth stage was less severe potentially due to additional time for crop recovery from regrowth of plants damaged at early compared to later stages. For hail damage at later growth stages, the ability of plants to recover and compensate for damage decreases due to less time remaining in the growing season.

Additionally, plant energy during the reproductive stages is invested in the development of reproductive organs and seed growth, thus making the recovery from damage less likely. Compared to damage inflicted at the early growth stage, the loss of yield was 2.7 to 3.8 times greater for field pea, and 1.2 to 4.8 times greater for beans from the same degree of damage when it occurred during the late stages of plant growth. While the damage to growing points in pulse crops in the early growth stages can still reduce yields, plants may recover by continuing to develop from dormant buds within a few weeks of the damage.

However, as the crop developmental stages advance, the impact of hail injury on crop yield can be more difficult to overcome and therefore result in more pronounced effects. As a result, many crops are generally able to recover from some leaf defoliation in the early vegetative stages, while leaf and stem damage in the later stages may lead to significant reduction in yield. Additionally, hail damage to pods can result in poor seed development or shattering of pods. In addition to direct yield loss, stem damage in later stages can cause lodging of crops, thus leading to additional losses during crop harvest.

Overall, the average yield for wheat decreased from 5200 kg ha-1 for untreated control to 3954 kg ha-1 (24% decrease) for light damage, and to 3377 kg ha-1 (35% decrease) for heavy damage (Figure 5). No significant reduction in wheat yield was observed when hail damage occurred at early growth stage, regardless of hail severity. Largest reduction in wheat yield occurred with heavy hail severity at late growth stage (BBCH 60) resulting in 55% yield loss.

Dry bean yield decreased from an average of 2574 kg ha-1 for untreated control to 2138 kg ha-1 (17% decrease) for light damage, and to 1745 kg ha-1 (35% decrease) for heavy damage. Yield reduction in dry beans was not statistically significant for light hail damage during early growth stage, but it increased to 41% for heavy hail damage during late growth stage.

Field pea yields were most affected, with the average yield decreasing from 4082 kg ha-1 for untreated control to 2566 kg ha-1 (37% decrease) after light damage, and to 2242 kg ha-1 (45% decrease) after heavy damage. Field pea yield reduced by 14 and 21% for light and heavy hail damage, respectively, during early growth stage, but the reduction in yield increased up to 66% for heavy hail damage during late growth stage.

Figure 5: Change in yield (%) for the light and heavy damaged treatments compared to untreated control for dry bean, field pea and wheat.

The application of nutrient blends and fungicides to the crops did not significantly improve stand density, crop height, NDVI, yield and seed weight compared to the check without any foliar fungicide and nutrient blend application nor were there any significant interactions with hail timing or severity.

Crop yield did not significantly change or show any pattern of increase for the plots treated with fungicide or supplemented with nutrient blends, compared to the untreated control without foliar applications for wheat, field pea or dry bean (Table 1). These findings are in agreement with other studies that did not find an increase in yield in response to application of fungicides in hail-affected crops such as corn, soybean and dry beans. Our results showed no benefit, or harm, associated with application of foliar-applied fungicides and nutrient supplements as hail-recovery tools.

Table 1: Effect of foliar application of fungicide and nutrient blends on the yield (kg ha-1) of wheat, field pea and dry bean averaged across the hail severity levels, hail timing treatments, and study locations from 2016 to 2018.