Hail storms are common across the U.S. this time of year. Assessing the damage to a soybean crop following a hail event can be challenging because it is difficult to determine the full impact until a few days after the storm. Ideally, an accurate assessment of viability of soybean plants should be determined seven to 10 days after the event. Potential yield loss of a soybean crop due to hail damage can be caused by several factors: leaf defoliation, plant bruising and stand loss. To assess the extent of hail damage to the soybean crop, the severity of each of these factors should be determined.
It should be kept in mind that leaf defoliation usually appears worse immediately after a hail event than it may be; that is why it’s important to wait the seven-10 days to assess the crop. Prior to flowering, a soybean plant can branch out after defoliation or stand reduction. If any of the axillary buds are viable after the hail event, new branches and leaves can still be produced from that plant. In addition, any leaf tissue remaining can continue to produce photosynthates for that plant. Plants with damage later in the growing season during pod fill may not be impacted a great deal by leaf loss, but be sure to count the number of damaged pods. Photosynthesizing plants can continue to fill pods that are already on the plant. Defoliation can also impact weed control in the damaged field. Leaf loss allows sunlight to reach small weed escapes; therefore, counting weed escapes should be a part of the scouting plan to help determine in-season and prior-to-harvest weed control measures.
Stem bruising can also affect soybean health and stands. Bruising can lead to lodging later in the growing season as well as provide an opening for infection to enter the plant. A fungicide application after a hail event can help control fungal infections such as anthracnose and soybean rust.
The final factor in determining the potential for yield loss due to hail damage is stand reduction. Stand reduction is determined by the number of plants lost post-storm. Start by counting the remaining plants to determine post-storm stand vs. pre-storm stand counts. There is usually little yield loss if the remaining stand is uniform with a population of 120,000 plants per acre or greater.
Leaf defoliation, stand reduction, disease and weed control, and environmental conditions are all factors involved in evaluating soybean hail damage and the potential for yield loss. Assessing yield loss due to damaged pods, reduction in stands, disease and weed competition following a hail event are only estimations.
Recovery and assessment of hail damaged soybean. Agronomy ALERT. Channel.com. http://www.channel.com/agronomics/Documents/AgronomicContentPDF/RecoveryandAssessmentofHailDamagedSoybeanChannelAlert.pdf.